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As outlined in my new Garage Build thread, we added a boiler to heat the new garage with hydronic in floor heat. The Lochinvar boiler we went with has up to 4 zones (thermostats) that we can hook up to it. I buried an insulated PEX loop out to my pole barn where I have my main shop. So one end (with a pair of 1" PEX lines) comes up in my mechanical room in the new shop, the other in the pole barn. Today I am heating the pole barn with a forced air NG hanging style shop heater. I will likely leave that in place for the time being but am looking at heating the shop with a water to air heat exchanger. This is the one I think I will buy.

https://www.amazon.com/Hydronic-hanging-heater-Variable-WIRING/dp/B077V63CM1

So to operate something like this I will need a way to call for the boiler to kick on and generate heat as well as trigger the pump to pump glycol out to the pole barn. I will also need to trigger the fan on the water to air heat exchanger to kick on. I will run a thermostat wire from the boiler to the pole barn via conduit that will be shared with the fiberoptic cable for internet. Shouldn't be an issue mixing low voltage with glass in the same pipe. That will allow me to install a thermostat out there to trigger the boiler and pump however how do I trigger the fan? Am I going to need two thermostats? My thought is to put a probe on the return loop or in the heat exchanger somewhere to detect a temp warmer than say 80F and kick on the fan. This way the call for heat controlling the boiler/pump will start circulating warm fluid, once it gets to the heat exchanger it detects it or the return loop heating up and kicks on the fan. Once the air temp hits my target the boiler/pump cuts out but the fan would keep running until either the return loop or heat exchanger drops in temp below whatever it is set at. The only problem is that the fan would try and run all summer unless I set it to something like 110F or just turn it off in the summer which is likely what I would do. Might as well keep using the warmth in the exchanger for a bit even though the boiler/pump kicked off. The boiler will send 160F to the pole barn and I expect some heat loss but it will be very minimal the majority of the run is under the new garage which has a heated floor, and it is about 15' from the new garage to the pole barn where it would be in frozen ground. I think the PEX is rated to 1F loss per 100' Total run is probably just shy of 70'. So I expect to basically have 160F liquid.

So, my question is if anyone has a setup like this and if so, how do you control both the boiler/pump and line voltage to the fan? Is there a single thermostat that will do this or am I better off going with two thermostats with a probe on the heat exchanger and a separate air thermostat to trigger the boiler/pump.
 

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I didn’t look real closely at the unit you linked...

I used to sell these things years ago. These would have their own fan limit control in them just like a furnace (hot air) would.

When the thermostat calls for heat the boiler will fire along with the circulating pump. As the heat exchanger warms up the fan limit control will sense the temperature and start the fan when appropriate. Then of course the opposite when cooling down.

The specs didn’t say if a fan limit control is included or not. That is what you will need for the fan to come on and turn off as certain temps of the heat exchanger.
 

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Ok, I'll give this a shot, but I'll have to re-read your spec a couple times....:lol:

Yes, you can do it with one stat.

You will need a couple relays. Relay In a Box, by Functional Devices. RIBU1C - single pole, double throw. RIBU2C, double pole, double throw. Coil has connections for 24vac & 120.

I would also use a temp sensor on the pipe to keep the fan from running till the flow is hot.

Stat makes, pulls in fan contactor, but fan doesn't start because pipe sensor wired in series is still open.

Stat also makes 2 pole relay at the boiler, one starts zone pump, other contact start boiler.

Water gets hot, pipe sensor makes, fan turns on.

Shop gets warm, stat opens.

Boiler should stop when the stat opens.

If you want the pump & fan to continue, you can use a time delay off relay, or you can use another pipe sensor to keep them energized (like a latching relay) until the pipe is cool.
 

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Discussion Starter #4
I didn’t look real closely at the unit you linked...

I used to sell these things years ago. These would have their own fan limit control in them just like a furnace (hot air) would.

When the thermostat calls for heat the boiler will fire along with the circulating pump. As the heat exchanger warms up the fan limit control will sense the temperature and start the fan when appropriate. Then of course the opposite when cooling down.

The specs didn’t say if a fan limit control is included or not. That is what you will need for the fan to come on and turn off as certain temps of the heat exchanger.
So they sell four versions. Well packages I guess is a better term.

Water to Air Heat Exchanger alone then bundled with different combinations of things like a rheostat to control fan speed and a thermostat.

The thermostat that they offer I looked up.

https://www.amazon.com/LuxPro-Programmable-Thermostat-Heating-Cooling/dp/B079GL1TQZ

But the issue is this appears to plug into an outlet and then the fan plugs into this. Also the temp prob is pretty short and on the back of the thermostat so only senses air temp. Then it is programmable for weekdays and weekends for different temps. Yeah don't care about that. I normally keep the shop at 36f or so all winter and bump to 60f when working out there. It also doesn't appear to have an output to low voltage to power the boiler/pump. Because of these reasons I was going to skip the thermostat.

I was looking at getting the bundle with the rheostat. Not that I feel the need to control the fan speed, maybe it would be nice, but for some reason it is cheaper to get the one with the optional rheostat than without. :dunno:

I guess you are touching on my question, I don't see anything that is a fan controller, I guess I could order one and see what happens when I plug it in. If the fan turns on then there isn't a controller. That is where I was thinking I could make one with a second thermostat with a probe on the heat exchanger to detect that the boiler is heating something and then it triggers the fan. In homebrewing I have a similar thermostat like this to control my fermentation process. It is a dual stage thermostat that can trigger cooling (turn on a fridge) or heating (turn on a heating element in the fridge) so that I can maintain whatever desired temp I want.

This is what I used for that project and I could adapt one to act as a fan controller.

https://www.amazon.com/Inkbird-Temperature-Controller-Fahrenheit-Thermostat/dp/B0152LYY0I

I asked the boiler guy what I should add for this and what he thought it would cost. He said that the water to air exchanger would be around $1000, plus a thermostat for the boiler/pump and misc plumbing. Total he was thinking around $1500. This one in the amazon link is $300-400 depending on options. For the same 100,000 BTU heat exchanger. Now it might not have the fan controller that you mentioned but that is what I am trying to figure out. Worst case, I don't see why I can't just make my own with the one above for $15. Doesn't need to be all that fancy, just no need to run the fan 24x7. I just didn't know if there was an all in one option out there for a thermostat that can read air temp and a probe for the heating element. Then call for heat with the low voltage to the boiler/pump and line voltage for the fan.
 

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Discussion Starter #5
Ok, I'll give this a shot, but I'll have to re-read your spec a couple times....:lol:

Yes, you can do it with one stat.

You will need a couple relays. Relay In a Box, by Functional Devices. RIBU1C - single pole, double throw. RIBU2C, double pole, double throw. Coil has connections for 24vac & 120.
I might have one of these laying around I just don't remember what flavor of a RIB it is. My dad gave me one years ago when he never had a use for it but I haven't found one either. Now where did that go. :dunno:

I would also use a temp sensor on the pipe to keep the fan from running till the flow is hot.
Yeah this is what I was thinking either on the return run or the heat exchanger. I was leaning toward the return only because if the boiler/pump shuts down, and the inlet pipe may stay hotter than whatever my fan cutoff temp is set to, it will keep the fan going long after the heat exchanger isn't producing heat. That is also why I think it might be better on the heat exchanger somewhere vs on the pipe. Once there is flow of 160f liquid the heat exchanger should get to temp quick. I also don't really care about what the temp of the pipe is to control the fan, the heat exchanger is heating the air being blown by the fan.

Stat makes, pulls in fan contactor, but fan doesn't start because pipe sensor wired in series is still open.
Can the pipe (or heat exchanger) take line voltage and how would I set it? I assume that would basically be another thermostat unless I wired in a thermistor in series.

Stat also makes 2 pole relay at the boiler, one starts zone pump, other contact start boiler.
The Lochnivar boiler has controller built in for 4 zones (pumps) so I run the Tstat to the boiler, that will control my pump.

Water gets hot, pipe sensor makes, fan turns on.

Shop gets warm, stat opens.

Boiler should stop when the stat opens.

If you want the pump & fan to continue, you can use a time delay off relay, or you can use another pipe sensor to keep them energized (like a latching relay) until the pipe is cool.
I could do a time delay relay. I think that STC1000 thing I posted above will do that. I know there is a start delay that I can program in. I use that to keep from short cycling the compressor on my fridge in the fermentation process. So basically backwards but if I am sensing the temp at the heat exchanger I don't need to get that fancy. Lets say I set it to 80F. Well if the boiler kicks out because the shop hits the target air temp, the fan would keep blowing across the heat exchanger until that probe hits 80F. Same effect. I just figured why not keep the fan blowing, I just would want it set to a temp greater than what I would call for. I could go 110F because we rarely hit that temp in the summer around here but that is still quite a bit of usable heat which could be circulated in the shop. I can always shut it down in the summer. I do that today with the NG furnace.

While I think your solution will work, I wonder if from a complexity standpoint it really isn't much difference than just doing two thermostats. One sensing heat at the heat exchanger and let it control line voltage of the fan. The other sensing air temp and controlling the boiler/pump.
 

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So they sell four versions. Well packages I guess is a better term.

Water to Air Heat Exchanger alone then bundled with different combinations of things like a rheostat to control fan speed and a thermostat.

The thermostat that they offer I looked up.

https://www.amazon.com/LuxPro-Programmable-Thermostat-Heating-Cooling/dp/B079GL1TQZ

But the issue is this appears to plug into an outlet and then the fan plugs into this. Also the temp prob is pretty short and on the back of the thermostat so only senses air temp. Then it is programmable for weekdays and weekends for different temps. Yeah don't care about that. I normally keep the shop at 36f or so all winter and bump to 60f when working out there. It also doesn't appear to have an output to low voltage to power the boiler/pump. Because of these reasons I was going to skip the thermostat.

I was looking at getting the bundle with the rheostat. Not that I feel the need to control the fan speed, maybe it would be nice, but for some reason it is cheaper to get the one with the optional rheostat than without. :dunno:

I guess you are touching on my question, I don't see anything that is a fan controller, I guess I could order one and see what happens when I plug it in. If the fan turns on then there isn't a controller. That is where I was thinking I could make one with a second thermostat with a probe on the heat exchanger to detect that the boiler is heating something and then it triggers the fan. In homebrewing I have a similar thermostat like this to control my fermentation process. It is a dual stage thermostat that can trigger cooling (turn on a fridge) or heating (turn on a heating element in the fridge) so that I can maintain whatever desired temp I want.

This is what I used for that project and I could adapt one to act as a fan controller.

https://www.amazon.com/Inkbird-Temperature-Controller-Fahrenheit-Thermostat/dp/B0152LYY0I

I asked the boiler guy what I should add for this and what he thought it would cost. He said that the water to air exchanger would be around $1000, plus a thermostat for the boiler/pump and misc plumbing. Total he was thinking around $1500. This one in the amazon link is $300-400 depending on options. For the same 100,000 BTU heat exchanger. Now it might not have the fan controller that you mentioned but that is what I am trying to figure out. Worst case, I don't see why I can't just make my own with the one above for $15. Doesn't need to be all that fancy, just no need to run the fan 24x7. I just didn't know if there was an all in one option out there for a thermostat that can read air temp and a probe for the heating element. Then call for heat with the low voltage to the boiler/pump and line voltage for the fan.
What I had in my mind was a hydronic controller - one that has a probe that is in the liquid flow from the boiler. Of course the heat exchanger would have to have a port for said probe.

Thinking more it would be overkill for your situation.

The LuxPro thermostats you linked would be a simple solution. It will be sensing the air temp adjacent to the unit. However it will turn the fan on and off with the change in the ambient air temp and not the temp of the liquid in the system which is what I was going for.

There would be no way to accurately sync the system thermostat and the luxpro thermostat. But that may not be a big deal as long as you got them close. What may happen is the luxpro thermostat may kick the fan on before hot liquid is flowing through the heat exchanger.

One other benefit of a true fan and limit controller is they are designed to kick the boiler burner off if it reaches the preset limit. In a situation where the boiler didn’t shut down when it should the fan/limit controller would shut it down before the system got too hot and caused damage.

So for my idea - you want something that will kick the fan on when the heat exchanger itself reaches a certain temp - then shut the fan off when the heat exchanger cools to a certain point. So something with a probe or sensor at the heat exchanger itself. It can and should act independently of the thermostat itself which is controlling the boiler and circulating pump.

I’m trying to digest rtgt’s theory of operation.
 

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As outlined in my new Garage Build thread, we added a boiler to heat the new garage with hydronic in floor heat. The Lochinvar boiler we went with has up to 4 zones (thermostats) that we can hook up to it. I buried an insulated PEX loop out to my pole barn where I have my main shop. So one end (with a pair of 1" PEX lines) comes up in my mechanical room in the new shop, the other in the pole barn. Today I am heating the pole barn with a forced air NG hanging style shop heater. I will likely leave that in place for the time being but am looking at heating the shop with a water to air heat exchanger. This is the one I think I will buy.

https://www.amazon.com/Hydronic-hanging-heater-Variable-WIRING/dp/B077V63CM1
Before I comment on anything else, will your plan here even work well enough even if you can find the correct controls?

What temps is your boiler heating water/glycol to?

Typically, hydronc in-floor heating systems use water temps at 85-125 degrees.

That exchanger you are looking at is designed to be connected to a system for standard hydronic baseboards. Those systems typically heat water to 160-185 degrees.

If you are pumping water that is only 120 degrees in to that exchanger, you're going to have to wait an awful long time before your shop ever warms up.
 

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Discussion Starter #8
What I had in my mind was a hydronic controller - one that has a probe that is in the liquid flow from the boiler. Of course the heat exchanger would have to have a port for said probe.

Thinking more it would be overkill for your situation.

The LuxPro thermostats you linked would be a simple solution. It will be sensing the air temp adjacent to the unit. However it will turn the fan on and off with the change in the ambient air temp and not the temp of the liquid in the system which is what I was going for.

There would be no way to accurately sync the system thermostat and the luxpro thermostat. But that may not be a big deal as long as you got them close. What may happen is the luxpro thermostat may kick the fan on before hot liquid is flowing through the heat exchanger.

One other benefit of a true fan and limit controller is they are designed to kick the boiler burner off if it reaches the preset limit. In a situation where the boiler didn’t shut down when it should the fan/limit controller would shut it down before the system got too hot and caused damage.

So for my idea - you want something that will kick the fan on when the heat exchanger itself reaches a certain temp - then shut the fan off when the heat exchanger cools to a certain point. So something with a probe or sensor at the heat exchanger itself. It can and should act independently of the thermostat itself which is controlling the boiler and circulating pump.

I’m trying to digest rtgt’s theory of operation.
The luxpro I linked to only seems to provide the ability to switch the line voltage. Sure I could go with a relay in a box like what rtgt mentioned but to close a low voltage circuit back to the boiler. If I mounted the luxpro to the side of the heat exchanger it might all work fine because as the coils heated, it would heat the sides of the box but that might just cut off the boiler. The other problem with this is I would have to climb up a ladder to get to the heat exchanger to change the temp when I am working out there.

This is why I keep going back to two separate thermostats like you also indicated. One to sense the temp of the liquid (to control the fan) and the other to sense the temp of the air (to control the boiler/pump). Unless someone makes a single thermostat that has two probes and can control line and low voltage. I could do something in the plumbing to actually sense the liquid temp. Again going back to homebrewing. I use thermowells in my kettles so that I can get temp readings of the wort during different stages of brewing. I then use a computer to control the electric heating elements. Same thing could be used to get a reading in the plumbing but I think it is overkill as I don't need accuracy to a 1/100th of a degree to control a fan. I am just thinking of sticking a probe in the heat exchanger somewhere. As long as the fan doesn't hit it, it should be fine. There are some thermowells in the installation right now but those are back at the boiler and too far away to control the fan. They are also before the splits to the zone pumps.

I am sure the more expensive water to air heat exchangers do this with something integrated but some of those are in the $1000 range. It isn't that I am cheap but if I can accomplish the same thing with a $15 thermostat, why spend close to $700 more to have it built in. It would be one thing if it is was in my livingroom. This is my shop.
 

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Discussion Starter #9
Before I comment on anything else, will your plan here even work well enough even if you can find the correct controls?

What temps is your boiler heating water/glycol to?

Typically, hydronc in-floor heating systems use water temps at 85-125 degrees.

That exchanger you are looking at is designed to be connected to a system for standard hydronic baseboards. Those systems typically heat water to 160-185 degrees.

If you are pumping water that is only 120 degrees in to that exchanger, you're going to have to wait an awful long time before your shop ever warms up.
For the floor hydronic zones there is a mixer that will limit the glycol/water mix to 120F or so. For the pole barn zone it will be before the mixer so it can get full 160F but great question as I didn't mention it. I will also be adding another zone and put another water to air heat exchanger in my furnace plenum but that is for a later project. Doing the pole barn now.

I don't have a great photo of how it is plumbed in the mechanical room but I can take one to show how he did it when I get home.

I will also still have the NG forced air hanging furnace out there. Depending on how things operate in real world vs theory right now, I can at a worst case use hydronics to keep the shop at 34-36. Then when I go out there to work use the NG forced air to kick it up to 60F. It can do that just fine.

The shop is roughly 32x32 insulated. Not sure of the R value. I also have a wood stove out there I use from time to time if I am going to be out there all day.
 

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I have one of these for a homemade control system for the solar panels on my pool.
https://www.amazon.com/bayite-Fahrenheit-Digital-Temperature-Controller/dp/B011VGASLW

It's lived outside for 3 years now and still works perfectly.

There are multiple program modes but if you tape the temp probe to the water pipe on the heat exchanger you can set the unit to turn the fan on when it gets warm and shut the fan off when the water is cold.

As for triggering the boiler loop you would need a second regular thermostat to control the space air temp.
 

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Yeah this is what I was thinking either on the return run or the heat exchanger. I was leaning toward the return only because if the boiler/pump shuts down, and the inlet pipe may stay hotter than whatever my fan cutoff temp is set to, it will keep the fan going long after the heat exchanger isn't producing heat. That is also why I think it might be better on the heat exchanger somewhere vs on the pipe. Once there is flow of 160f liquid the heat exchanger should get to temp quick. I also don't really care about what the temp of the pipe is to control the fan, the heat exchanger is heating the air being blown by the fan.

The sensor, mounted on the pipe or heat exchanger is just to tell you the system is hot. The temperature of the water in the supply line is the most consistent. Something like a TE91, straps directly to the pipe.

If you are running 160 degree water, the sensor could be set for 140 - 150 degrees. I doubt you'll see that kind of pipe temperature in the summer either so you shouldn't have to mess with it.

It doesn't actually have to be used to keep the fan running. Sometimes you want the load to stay on the system (fan running) until you can move the heat out of the boiler with the pump. Boiler goes off, pump and the fan stay on until the system temp starts to drop, indicating that the heat load is out of the boiler, then the pump and fan are turned off.


Can the pipe (or heat exchanger) take line voltage and how would I set it? I assume that would basically be another thermostat unless I wired in a thermistor in series.

I attached a spec sheet of the TE9x series strap on sensor. It is rated for 250vac.

If you have a low volt stat, then you'll need a 24vac transformer. If you use a stat and pipe sensor rated for line voltage you are good to use line voltage. Just use an isolation relay like a RIB because likely the boiler connection has its own power source. The RIBU1C has either a 24 or 120 coil.



The Lochnivar boiler has controller built in for 4 zones (pumps) so I run the Tstat to the boiler, that will control my pump.

:good2: Then the boiler likely also has a timer to keep the pump running for a time period once the call for heat is removed.

Since the pump control is packaged with the boiler it probably doesn't matter if you keep the fan running after the room stat kicks out since the pump will stop in 2 to 5 minutes after the boiler is stopped. If you wanted to keep the fan running to get whatever heat is left, the an off delay relay would be the easiest. Just time how long the boiler controller keeps the pump running and set the off delay relay for the same about of time. Once the pump is off, there is no need to keep the fan on.



While I think your solution will work, I wonder if from a complexity standpoint it really isn't much difference than just doing two thermostats. One sensing heat at the heat exchanger and let it control line voltage of the fan. The other sensing air temp and controlling the boiler/pump.

It would look a lot easier if I could draw it first, then explain it. I also was thinking that the pump wasn't part of the boiler package.

Room stat calls for heat.
The coil of Boiler enable relay (R-1) is wired to just the room stat.
Contacts of relay R-1 close and enable packaged boiler & pump to start.
Water gets hot.
Pipe stat contacts close.
The coil of the Fan enable relay (R-2) is wired in series with room stat and the pipe stat. When R-2 is energized, the fan is enable to run.
R-2 can be a normal relay, or an off delay relay.

See comments in blue.
 

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Discussion Starter #13
Before I comment on anything else, will your plan here even work well enough even if you can find the correct controls?

What temps is your boiler heating water/glycol to?

Typically, hydronc in-floor heating systems use water temps at 85-125 degrees.

That exchanger you are looking at is designed to be connected to a system for standard hydronic baseboards. Those systems typically heat water to 160-185 degrees.

If you are pumping water that is only 120 degrees in to that exchanger, you're going to have to wait an awful long time before your shop ever warms up.
Jim, I took some pics of the setup.

In this one you can see the pipes coming from the boiler which is out of frame to the right. They go into the green tank which allows for sediment to drop out and trap any air in the system. From there you can see where they end to the left edge of the shot. The top pipe is the hot side from the boiler and the lower one will be the return loop. Where those pipes end, we will have the pump for the zone going to the pole barn. Also the green pair of PEX is the loop that goes to the pole barn. The mess of blue PEX will be either water lines, runs for fiberoptics to the other buildings and one will be shared with thermostat wire to the pole barn.



This second shot is a little higher on the wall from the first. You can see the green knob in the middle/bottom of the shot. That is the mixing valve which will mix in cool return glycol/water with some hot to make 120F to supply all loops to the floor heat. You can see the one pump in place for the garage floor. Above this pump out of frame is a split with a pair of valves that will open and close to either send glycol/water to either the garage floor or mud/laundry room. Not sure what the other valve is for that dead ends in the upper right. Maybe that is a system fill point. I wasn't here when they filled it.

 

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Discussion Starter #14
I have one of these for a homemade control system for the solar panels on my pool.
https://www.amazon.com/bayite-Fahrenheit-Digital-Temperature-Controller/dp/B011VGASLW

It's lived outside for 3 years now and still works perfectly.

There are multiple program modes but if you tape the temp probe to the water pipe on the heat exchanger you can set the unit to turn the fan on when it gets warm and shut the fan off when the water is cold.

As for triggering the boiler loop you would need a second regular thermostat to control the space air temp.
Yeah that is similar to the STC1000 that I have used for fermentation control. I think it is a single which is what I would need. For home brewing I am using a dual stage so I can set the desired temp and an offset. So lets say 50F +/- 2F and it will either run the fridge or heating element to keep it right at that temp.
 

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Discussion Starter #15 (Edited)
See comments in blue.
The one gottcha I might have is that while the boiler should supply 160F liquid. There is a scenario where it will be lower.

If you look at the first photo above the green tank looking thing is a Caleffi Hydro Separator. Because of the mixing valve for all in floor heat this likely wouldn't happen very often but it is possible where the main pump on the boiler can't pump enough GPM to keep up with the demand of the heating loops. For instance if everything is calling for heat at once. Because we are running the boiler at a higher temp (160F) than what is going to the floor loops (120F) they should only see a slight GPM pull to bump the temp back up to 120F before getting sent back out to the zone. However if everything is heating at once wide open. For instance on first start in the fall. What will happen is if the boiler pump can't keep up, the fluid on the return loop will hit the Caleffi Hydro Separator and some of the volume will get sucked up to the top of the tank and back out to the loops. The idea is as follows just making up numbers for an example.

main boiler pump 20GPM
all loops open 25GPM demand

In that case the boiler is running 20GPM at 160F which hits the Hydro Separator and then there is a deficit of 5GPM so that gets sucked up and mixes with the hot 160F liquid and will drop it a bit in temp until some of the zones stop calling for heat by closing their valves. As they close off the demand will dip from 25GPM to maybe 18GPM. Now the main boiler pump can keep up and 160F liquid will start going to the pole barn.

The idea of this is without it, some of your individual loops in a zone can suck 100% return fluid and the first couple loops will get all the heat until they start to balance out. This is where you get uneven heating. With the Hydro Separator all loops in a zone might get slightly lower temp liquid until zones start shutting down. It will come down to how often all zones are calling for heat at once which shouldn't be very common.

That is one of the reasons I was thinking about running a thermostat at a lower temp than 120F. I should always get that much heat or more in theory but we will see in practice.
 

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The one gottcha I might have is that while the boiler should supply 160F liquid. There is a scenario where it will be lower.

That is one of the reasons I was thinking about running a thermostat at a lower temp than 120F. I should always get that much heat or more in theory but we will see in practice.
:good2: The pipe stat has a setpoint range of 68 to 194 degrees. It is really there just to tell you you have hot enough water to heat with.

If the pole barn isn't a high priority, maybe keeping the pipe stat set at 140+ will allow the other three zones a chance to catch up without mixing if you were to get into a full load situation.

Either way, you have a pretty good range to play with.

Thinking about the fan running in the summertime I realized it if is hot enough in the summer to allow the pipe stat to make even as low as 120 degrees, the zone stat shouldn't be made with a typical heating setpoint (70 degrees or less).
 

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Discussion Starter #17 (Edited)
:good2: The pipe stat has a setpoint range of 68 to 194 degrees. It is really there just to tell you you have hot enough water to heat with.

If the pole barn isn't a high priority, maybe keeping the pipe stat set at 140+ will allow the other three zones a chance to catch up without mixing if you were to get into a full load situation.

Either way, you have a pretty good range to play with.

Thinking about the fan running in the summertime I realized it if is hot enough in the summer to allow the pipe stat to make even as low as 120 degrees, the zone stat shouldn't be made with a typical heating setpoint (70 degrees or less).
I will have to look at the spec on it again. I guess I read it wrong. I was thinking it was saying that there were three different ones with different points that were set at the factory. I missed that they were adjustable.

Even if it were set to a point where the air thermostat would call for heat, we are going to be programming the boiler today. One of the settings on the boiler is for outside temp cutoff. The boiler will be set so that if the outside air temp is greater than 70f (I think that is where we are going to set it) the boiler completely shuts down. There isn't any space that I will heat greater than that so it won't be possible for someone to mess with or bump a thermostat and call for heating a zone to 90 in the middle of summer. It is really just to save wear and tear on the fan to not have it run all summer if the temp of whatever I am measuring went about the cut in temp for the fan. Or just turn it off in the summer. That is what I do with my hanging forced air furnace. I just shut the breaker off.

I will get the water to air heat exchanger ordered up. I did ask on Amazon if it had any form of fan controller other than the thermostat and someone replied that it does not. If the fan has power it will run.

Once it gets here and I have some time to play around with it and work out how I want to plumb it, I can figure out what method will work best. I will be running the pex up the wall and transition to copper. When I do that I can easily put in a T rather than an elbow somewhere and either go with a thermowell or probe in the liquid or just stick something in the heat exchanger.

I was mainly wondering if there was some thermostat out there where one unit could do everything but was coming up with nothing as it is kind of a different situation. I figured it could be done with a series of relays and probes or two separate thermostats but I wasn't sure what the best option was.
 

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I would approach it one of two ways:

1. Honeywell manufacturers a hot water sensor that would clamp to the feed pipe, assuming you have a stub of copper or some other rigid piping long enough before the PEX connection. They'll switch line voltage. It, by itself, will control the fan. I've seen these quite a bit on hot water systems with multiple radiators on a single zone. This would be the simplest.

2. Utilize a Honeywell Fan/High Limit controller that is normally utilized in a forced air furnace. The probe will need to be inserted so it receives air flow from the fan. I added one of these to an overhead NG Bryant unit heater 20+ years ago, in our former business building. When we acquired the building, the Bryant heater was in place and recently had the heat exchanger replaced, so it was a solid unit. It was just way too big (BTUs) for the garage it was heating, especially once the overhead door was replaced with an insulated door and the block walls were stripped and insulated. So it would short cycle frequently. It just had a delay timer on the fan, as part of the standard wiring. The problem with that was the delay timer was not adjustable and it would run too soon and too long. So it was always blowing cold air on us when we worked in the garage. It was fairly uncomfortable.

After putting up with it for a few heating seasons, I finally said enough was enough. I fabricated a mounting plate from some heavier gauge galvanized sheet metal to fit into the corner. I mounted a fan/limit switch normally utilized in a forced air furnace on to the sheet metal plate I had fabricated. I then bent conduit an attached from the limit controller to the electrical cabinet at the rear of the unit. Once I had it wired up a few a trial and error adjustments followed. It worked great for the next 20+ years! We sold the building a few years back, but I think it is all still in place.

Whatever you decide to do, you want something that is not going to be blowing cold air on you.
 

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Discussion Starter #19
I would approach it one of two ways:

1. Honeywell manufacturers a hot water sensor that would clamp to the feed pipe, assuming you have a stub of copper or some other rigid piping long enough before the PEX connection. They'll switch line voltage. It, by itself, will control the fan. I've seen these quite a bit on hot water systems with multiple radiators on a single zone. This would be the simplest.
Are you talking about something like this?

https://www.amazon.com/Honeywell-T675A1425-temperature-contol-capillary/dp/B0009784L6

As another example I have used this one which is a digital version of basically the same thing.

https://www.amazon.com/Johnson-Controls-A421ABG-02C-Electronic-Temperature/dp/B01IWIZJHA

I have used both as Keggerator controls as I can better control the temp vs the internal thermostat that just is a random number that doesn't match a temp. For a while I was using the Johnson Controls version with the forced air furnace in my pole barn. I was using this because I could set the temp at 36F and program in the offset that I wanted. Before that the Honeywell round mercury switch style thermostat could only be set down to 60F. I couldn't find a thermostat at Menards at the time that went below 60F as they were all designed for the home. Keeping the shop at 60F was killing me financially and I had the Johnson Controls Thermostat sitting there not really doing anything. The only complaint was it was too hard to raise the temp one degree at time when I wanted it warmer out there so I wired in a toggle switch so I could switch back and forth between the old Honeywell and Johnson Controls. That worked well until I got another keggerator that I wanted to use the Johnson Control on and I found a slider Honeywell that went down to 36F.

I will have copper. The PEX runs about 6' up my 12' walls so I will transition from PEX to Copper and complete the loop. This is why I was looking for options on controlling the fan. Do I want to use a T rather than an elbow somewhere to add a thermowell and get a temp reading of the liquid (either on the hot side or return side) or do I just stick a sensor of some sort in the heat exchanger. I don't need the accuracy of being in the liquid for something like controlling the fan. So I will likely skip the thermowell option as there are more chances of leaks. I can just strap something to the side of the copper pipe and it would be fine or go inside the heat exchanger. Even something sitting on one of the copper 180 bends that most of these use should be fine. There are options.

2. Utilize a Honeywell Fan/High Limit controller that is normally utilized in a forced air furnace. The probe will need to be inserted so it receives air flow from the fan. I added one of these to an overhead NG Bryant unit heater 20+ years ago, in our former business building. When we acquired the building, the Bryant heater was in place and recently had the heat exchanger replaced, so it was a solid unit. It was just way too big (BTUs) for the garage it was heating, especially once the overhead door was replaced with an insulated door and the block walls were stripped and insulated. So it would short cycle frequently. It just had a delay timer on the fan, as part of the standard wiring. The problem with that was the delay timer was not adjustable and it would run too soon and too long. So it was always blowing cold air on us when we worked in the garage. It was fairly uncomfortable.

After putting up with it for a few heating seasons, I finally said enough was enough. I fabricated a mounting plate from some heavier gauge galvanized sheet metal to fit into the corner. I mounted a fan/limit switch normally utilized in a forced air furnace on to the sheet metal plate I had fabricated. I then bent conduit an attached from the limit controller to the electrical cabinet at the rear of the unit. Once I had it wired up a few a trial and error adjustments followed. It worked great for the next 20+ years! We sold the building a few years back, but I think it is all still in place.

Whatever you decide to do, you want something that is not going to be blowing cold air on you.
Something like this is what I assume you are mentioning as another option.

https://www.amazon.com/Honeywell-L4064B2228-limit-controller-insert/dp/B00097BE5O

I can look into that. It is a cleaner package for likely doing the same thing.

125 F fan on and 100 F fan off stops, 200 F high limit stop and 5 in. insertion.

I did order the water to air heat exchanger. It should be here in about a week. Maybe I will wait until it is here to look it over and see what is going to be the easiest to install.

I agree that I don't want cold air blowing on me. It would also cause the fan to run when it is summer all the time if set too low. Fan on at 120F should be warm enough where it wouldn't kick on in the summer. It is probably is a good compromise to allow it to get a little more heat out of the liquid in the heat exchanger rather than just cutting out when the air thermostat is no longer calling for heat from the boiler and pump.
 

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A well sensor is overkill.

The TE91 straps to the pipe. With a little thermal grease on a clean copper pipe this sensor will read as accurate as a well sensor.

The arrow points to the sensor block on the back of the sensor.

TE91.JPG

I would mount the pipe sensor on the pipe as close to the coil connection as possible. Once the pump shuts down, you won't have any flow and if the fan is running the heat exchanger will cool very quick. As long as the pump is running you will be able to use the remaining heat.

I would use an off delay relay, like the IDEC RTE series, for the fan control. Time the off delay the boiler uses to control the pump, then set the fan relay for that time.

You can always wire in a light switch on the side of the unit as a service switch to kill control power to the stats/relays. Usually by code this is required anyway.
 
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