Existing OWB to heat pole barn

[Sparky43]

Hello everyone! Tonight I stumbled upon this site and I love it.

Earlier this year my wife and I bought our house which has an OWB. The boiler is located about 30 yards from the house on the backside of my pole barn which is 30’ x24’. The previous owner sprung for the top of the line insulated lines for the supply and return.

I run the boiler as my primary heat and we have a propane forced air furnace as back up if it goes out. The OWB also heats our hot water heater.

So here is my plan and I’d appreciate some feedback and any wisdom anyone could impart. The pole barn (30’x24’) is currently uninsulated and has a crushed stone floor. My plan is to take the lines from the boiler and cut them as they pass by the pole barn and swing them into the barn, underground of course. Then pex the return around in the pole barn before heading back to the boiler which is just outside the back of the pole barn. The supply would just connect right in the pole barn and go straight into the house.

All lines would be reinsulated and poured in the slab of the pole barn floor. Then we plan on insulating the pole barn.

The questions this raises for me is with no way to control the heat in the pole barn I wonder what temperature it will be out there. The return is usually around 120 degrees (according to the previous owner). I’ve done my research as far as installing the pex radiant heating (vapor barrier, insulation, pex). If anyone has a similar system or any tips or tricks or tweaks I should make to this plan feel free to respond.

Thanks for taking the time to read this I appreciate any and all Input!
Ps I added a couple very rough drawings I did on some app I just bought to illustrate my plan. The lines approximately pass 3’ from the edge of the pole barn and run parallel lengthwise along the entire pole barn. Cutting the lines in the middle of the barn would give me more than enough “slack” to swing them into the barn.

 

[andym]

That would certainly heat the pole barn. I would advise you not to do it that way though. Others more knowledgeable on hydronics will be along soon, but for starters here are a couple problems I see: you already mentioned the fact that you would not be able to control temperature. It would almost certainly get too warm in the shoulder season. Another issue is that the return to the boiler would probably become way colder than preferred. Thirdly, I'm assuming the underground lines are 1". That would be overkill for using in a poured slab, but neither do you want to reduce it to 1/2".
The proper approach (I think) would be to run the insulated lines into the barn as suggested and install a T on both return and supply. Then add a small circulator pump connected to the supply T, loop the half inch lines through the floor and connect it to the return T. You can then control the pump via thermostat. You may also want to add a thermostatic tempering valve? An alternate method would be to simply run another separate insulated line from the boiler to the barn.

 

[Eureka]

Run another underground line from the OWB to a heat exchanger in the pole building. Basic radiant floor system running off of that.

 

[Eureka]

There is likely an extra supply and return port on the back of the OWB. If not, a tee can be put on to have 2 outputs; which is what I had to to. I have also seen people run a single supply output to a small manifold to pull extra loads from.
You would not be happy with your plan in the end.
-#1, and most importantly, you need to be able to fully regulate heat distribution in your pole building, or it will be emitting heat at the rate the slab can give it off all the time, no matter what, essentially ending up at whatever the return temperature is, so 180.
-It would be less than fun digging up a line in the middle of the yard without hitting it and damaging it.
-You would most likely have to upsize the circulator off the OWB bigtime to deal with the extra head, so more money in power used there. 2 small circulators pushing less fluid, a shorter distance will use less than 1 huge pump chugging along.

You need to treat them as 2 separate heating systems with 2 different supply and return routes, coming from 1 heat source.

Happy to help! But do a little more looking around first. Image search for OWB piping, OWB plumbing, OWB underground lines, etc. Its all pretty simple, and because of that, it is very easy to over complicate.

 

[Sparky43]

Thanks so much for the responses!

I’ve done a little more research and have attached a picture of my current set up. You can see the pump with the supply and return lines.

Near the lines are two black rubber caps covering square bolts. I’m assuming these are plugs for an additional supply and return line.

I’m excited because it’s far easier to run a new line 10’ than to dig up the existing one!

So this raises more questions. I would have to put a separate pump for the new lines as it’s a completely separate system. My current pump runs continuously. I’m assuming I would need to run a control wire to a thermostat in my pole barn so that the new pump would only turn on when it called for heat. Would I also have to add any control wiring for control valves and if so where in the system would they go?

 

[E Yoder]

I would not cut into lines underground.
To control the floor heat you'll need to start and stop the pump with a thermostat and relay. You'll need a mixing valve to temper down the water to approx 80-100 F going into the floor. 180F is way too hot. You'll scorch your feet and crack the slab.
With a mild steel boiler I'd probably separate the floor loops from the OWB water with an additional pump and flat plate heat exchanger.
Take your time and research it, radiant has to be done correctly.

 

[Highbeam]

How about a primary/secondary set up with a pump at the boiler constantly circulating water to the pole barn in a loop. On that loop, in the barn, a second pump that runs as needed to draw hot water from the loop for the slab and returns to the boiler loop.

 

[E Yoder]

Agree, with the secondary pump pulling through a mixing valve.

 

[Eureka]

Here is an example of a simple closed loop radiant floor system connected to a flat plate heat exchanger pulling heat from underground lines from an OWB.
I’ll snap a picture of the system I plumbed in my pole building using black iron pipe a few years ago when I get a chance.

The electrical side hasn’t been done in the photo, but all that is remaining here would be a Taco 501
1 zone switching relay (or equivalent), and a thermostat to tell the switching relay “Hey I need heat, turn on the circulator and give me warm water”. That’s it.
The circulators on the back of your OWB should run constantly pushing water around the loop out of the OWB, to the building, through the heat exchanger, and back out to the OWB. When your buildings want heat, thermostat asks for it, relay turns on circulator in building, cool water in the floor loops is pushed out and warm water pushed in, transferring heat from the heat exchanger until the thermostats are satisfied, and the circulator turns off. I have the mixing valve on my pole building sending 75 degree water to my floors to maintain 55 inside. It works very well. Thank you, spray foam.

 

[Highbeam]

Here is an example of a simple closed loop radiant floor system connected to a flat plate heat exchanger pulling heat from underground lines from an OWB.
I’ll snap a picture of the system I plumbed in my pole building using black iron pipe a few years ago when I get a chance.
View attachment 269668
The electrical side hasn’t been done in the photo, but all that is remaining here would be a Taco 501
1 zone switching relay (or equivalent), and a thermostat to tell the switching relay “Hey I need heat, turn on the circulator and give me warm water”. That’s it.
The circulators on the back of your OWB should run constantly pushing water around the loop out of the OWB, to the building, through the heat exchanger, and back out to the OWB. When your buildings want heat, thermostat asks for it, relay turns on circulator in building, cool water in the floor loops is pushed out and warm water pushed in, transferring heat from the heat exchanger until the thermostats are satisfied, and the circulator turns off. I have the mixing valve on my pole building sending 75 degree water to my floors to maintain 55 inside. It works very well. Thank you, spray foam.

What is the benefit of adding a heat exchanger and the expansion tank hardware when you could have just pushed boiler water through your floor? You created a second, isolated, pressurized system for the slab. Why?

 

[Sparky43]

Thanks for the continued responses!

I talked to my brother today who is a union plumber and has years of experience with these types of sysytems. He reaffirmed what you guys have told me.

I will add a small pump at the boiler with a loop to send hot water into my pole barn. this will run continuously. That will be hooked up to a heat exchanger in the pole barn. I will have a loop in there on a separate circulating pump which will be controlled by a relay attached to a thermostat as described above attached to the heat exchanger as well.

The only suggestion that he added was to use glycol in the pole barn floor loop so that if I ever lose heat at the boiler the pipes won’t freeze solid. This is common sense but I really hadn’t thought about it.

I’m a union electrician by trade so it takes me a little while longer than average to wrap my head around how these systems work. I feel like I have it on the run now .

Does anyone have any tips or suggestions about installing pex in the floor for the radiant heat. It seems pretty straight forward but it’s always nice to hear from someone who’s done it before and hear about the things that they wished they’d known.
Thanks again!

 

[Eureka]

What is the benefit of adding a heat exchanger and the expansion tank hardware when you could have just pushed boiler water through your floor? You created a second, isolated, pressurized system for the slab. Why?

That picture wasn’t mine, just pulled off google images, so I don’t know their logic. It was on heating help dot com

It is in general a poor practice to have an open in-floor radiant system.
Some potential cons:
-Persistent air problems
-Inconsistent flow / balancing through loops
-Shorter circulator life
-Potential corrosion in high points or air pockets
-More water to treat, test, and maintain
-Corrosion or nastiness in the outdoor unit gets pumped through the more delicate indoor hardware. This includes Asian beetles, box elder bugs, rust flakes, Teflon tape, silicone, or whatever else finds its way through the OWB vent. All
things I have seen in y strainers on the OWB feed
-Inferior heat exchange through emitters
-No option to add glycol for future freeze protection in accessory or seasonal buildings
-Susceptible to height and water level issues, especially during power outages

Potential pros:
-It’s cheaper
-It’s easier

All that being said, there are many many folks running their systems just like this, and they work great for them. I suspect that for every 3 homes running with open systems, 1 may have persistent issues. No disrespect meant to anyone doing this successfully, @E Yoder probably has lots of experience in this that would prove me wrong.

More boils down to what is accepted as right, vs wrong.

 

[Eureka]

Does anyone have any tips or suggestions about installing pex in the floor for the radiant heat

-Take your time with the details of getting the earth compacted and leveled, you want the foam flat and tight.
-Insulation is everything with in floor heat, so get it right. Slab edges can be most important. Anywhere concrete will be in contact with cold is a huge energy leech.
-Use a thick poly vapor retarder under the foam
-The stand up stapler with plastic staples is slick. One person unrolls and guides the PEX and the other routes and staples the pex.
-The staples are expensive, but use plenty so the tubing stays put during the pour.
-Consider sticking a 3/8” chunk of copper a few inches long in the concrete where you plan to have the thermostat so a slab sensor thermostat probe is an option
-12-18” on center with the tubing works well
-Keep loops under 250’ ideally, but not over 300’
-Mesh or rebar reinforcement over the PEX are good, but can puncture the tubing during the pour from wheelbarrows and walking, so be careful and use rebar stands or chunks of brick or CMU block to lift the rebar / mesh up off the PEX and suspend it in the slab.
-Have the supply and return manifolds in place and connected to the tubing so they can be pressurized with air during the pour. A schrader valve adapted to 1” pipe threaded into one manifold, and an air gauge adapted to the other. 30-40 psi and if a tube gets pierced, you should hear air or see bubbles. Have a couple PEX couplings there in case the dreaded happens. It rarely does unless you have silverback gorillas pouring the floor.

 

[Eureka]

OWB strainer:

Closed loop floor strainer:

These are on either side of a 40 plate FPHX that I cleaned for this season.

 

[salecker]

What is the benefit of adding a heat exchanger and the expansion tank hardware when you could have just pushed boiler water through your floor? You created a second, isolated, pressurized system for the slab. Why?

My guess he has antifreeze in his slab...

 

[Highbeam]

My guess he has antifreeze in his slab...

But not in the owb? I guess that would be a lot of antifreeze! So if you have to keep the boiler hot then why not keep the shop above freezing too.

Selfish questions, I have a shop with 1800 lf of unused pex tubes in a well insulated slab.

 

[Eureka]

So if you have to keep the boiler hot then why not keep the shop above freezing too.

In the case of a house and outbuilding being heated, one might not always have the outbuilding turned on or heated beyond freeze danger. I put some glycol in my pole building just in case I’m injured and can’t load wood. My house has backup but not my shop.

An OWB with circulators running will rarely freeze up. My OWB water stays about the temperature of my utility room throughout the off season with the circulator running. I left for 4 days in the middle of the winter and the temp of the water was 68.

 

[Sparky43]

The biggest question I have now is why use a mixing valve for the in floor loop? I don’t really understand why you would want your heated supply glycol mixing with your return from the floor.

 

[Eureka]

The biggest question I have now is why use a mixing valve for the in floor loop? I don’t really understand why you would want your heated supply glycol mixing with your return from the floor.

The mixing valve blends a little of the cooler return water with the hot supply to get the desired temperature out to the floor. Don’t want anything over 130-140 going to the concrete, and it’s usually much lower, like 100 degrees.
Think of the mixing valve like you standing at your bathroom sink and turning a little bit of the cold and hot to get a temperature that’s comfortable.
So it doesn’t actually mix the two systems’ fluid.

 

[E Yoder]

That picture wasn’t mine, just pulled off google images, so I don’t know their logic. It was on heating help dot com

It is in general a poor practice to have an open in-floor radiant system.
Some potential cons:
-Persistent air problems
-Inconsistent flow / balancing through loops
-Shorter circulator life
-Potential corrosion in high points or air pockets
-More water to treat, test, and maintain
-Corrosion or nastiness in the outdoor unit gets pumped through the more delicate indoor hardware. This includes Asian beetles, box elder bugs, rust flakes, Teflon tape, silicone, or whatever else finds its way through the OWB vent. All
things I have seen in y strainers on the OWB feed
-Inferior heat exchange through emitters
-No option to add glycol for future freeze protection in accessory or seasonal buildings
-Susceptible to height and water level issues, especially during power outages

Potential pros:
-It’s cheaper
-It’s easier

All that being said, there are many many folks running their systems just like this, and they work great for them. I suspect that for every 3 homes running with open systems, 1 may have persistent issues. No disrespect meant to anyone doing this successfully, @E Yoder probably has lots of experience in this that would prove me wrong.

More boils down to what is accepted as right, vs wrong.

I have always piped the outdoor boiler water in direct (with a mixing valve, etc) rather than separating with a flat plate. But I'm using all stainless boilers.
I just worked on an old mild steel unit last week that had filled the lines to the house with sludge to the point it had almost no flow. So trash coming through the lines can definitely be an issue.

 

[Sparky43]

I have always piped the outdoor boiler water in direct (with a mixing valve, etc) rather than separating with a flat plate. But I'm using all stainless boilers.
I just worked on an old mild steel unit last week that had filled the lines to the house with sludge to the point it had almost no flow. So trash coming through the lines can definitely be an issue

I have never really considered this being an issue. My system has nothing in place to filter any “gunk” from OWB loop to the house. How does one go about putting something like this in? I have plenty of access to the 1” pex in the house I would think that it’s as easy as putting in a couple shutoff valves with some sort of filter in between it.

 

[salecker]

I run antifreeze in my underground lines and house.
My boiler and storage are water,i have a y screen befor my heat exchanger on each side.Plus i run a side stream filter on the antifreez side. I was told that Antifreeze breaks down in a boiler,i have my oil back up on the antifreeze side so i wanted to make sure it was clean during use.I also used recycled copper from an old boiler system which had a coating in the pipes.The first sidestream filter pulged up after a week,the next one lasted 3 months,this one is still working years later.It has a flow glass on the downstream side so you can see it it is still flowing fluid.
My water remains crystal clear after 10 years

 

[Eureka]

I have never really considered this being an issue. My system has nothing in place to filter any “gunk” from OWB loop to the house. How does one go about putting something like this in? I have plenty of access to the 1” pex in the house I would think that it’s as easy as putting in a couple shutoff valves with some sort of filter in between it.

As @salecker said, a simple Y strainer is rock solid and easy to service with minimal loss of system fluid. Shut offs on either side. You can get them threaded, sweat, whatever. Cheap too. There are better options, but at higher cost.

Put it before circs and stuff you don’t want junk in.

 

[NateB]

Here is a crazy idea. Extend your pole barn around your wood boiler. There are many advantages to doing it, and very few if any negatives. The waste heat from the boiler would heat your building.

 

[Highbeam]

Can these things be “interior”?