Hello all! FNG here with some radiant heat floor questions.

GrafixxMan

Howdy from central KY (42754) everyone! Happy to be a new member, although I wish I didn't need to be. LOL! The wife and I built a 40x60x17 pole barn. It is insulated with 3" bat rolls on the walls and roof. They say they're R10-R19, but I'm guessing they're on the 10 side. The building sits on 4" of rock, then a 6mil vapor barrier and then the 2.5" "lego" type of insulated panels are under a 6" concrete slab. We have 8 250-300' runs of 1/2" pex. After the gravel was on grade, we did everything else ourselves. Now, I am not an expert at radiant floor heating (or anything for that matter) and I have some questions. I would absolutely appreciate any help. With that being said, we cannot afford to buy different pieces nor do we have the time to "redo" anything. I would very much like to make what we have work as well as possible.

So, a friend did his floor and it turned out great and he guided me thru buying the pieces I would need (the same pieces he has) minus the boiler. The building has a kitchen and a full bath. What we have for our system consists of:

Hydro Smart HSPS120LT 1 zone low temp integrator panel
Aube thermostat w/ floor sensor - hooked to above panel
Bluefin 8 loop stainless manifold
Navien NCB 240/130H combi boiler
250gal propane tank

The water heater was recommended by our plumber - who has never done a radiant system. He called his Navien rep and that guy recommended this model so we could heat the floor in closed loop and the potable water. He was just trying to help me out since I don't know what I don't know. I just knew I wanted heated floors in our garage. When we first got everything hooked up, the boiler wouldn't for for the floor...only the DHW side. No matter what we (the plumber and myself) tried, it just wouldn't come on. After a couple of days, he came back over and tried a dip switch. It instantly came on and man did it work! Unfortunately, it was pushing 170*+ water thru the lines. It went from 53* in the garage to 73* overnight. Because that dip switch was flipped, the boiler was just on... ALL the time. Unfortunately, we used 75gal of propane in 2.5 days! I knew that couldn't be right and Navien won't tell the customer how to do anything, so the plumber came back over and helped me once again. We were both learning at the same time. Turns out, we needed t-stat wires to go from the panel to the boiler...not just the from the panel to the t-stat. After doing that and "unflipping" the dip switch, now the boiler turns on and off as it should. Since we fired it up less than 2 weeks ago now, we've ran thru 150-160gal of propane!

We have an outdoor thermostat, but I had it disabled so I could turn the outgoing water temp down. With it enabled, I have no control of that and I've turned it down from 150 to 135 to 130 to 120 and now it's at 110. We've kept the garage at 55-60* and in 2 days time, it's used 10-15% of the propane. Certainly it shouldn't be using THAT much, should it? There are so many settings on this boiler and I don't know where they should be set and Navien won't tell you nor does the book that comes with it. Can someone please tell me where everything should be set at so we're not burning propane like it's out job to do so , PLEASE?

There was no heat loss analysis done. There was just a guy and girl with a will and a way and not scared to do it ourselves. Now that it's done, I want to make it right. Sorry for being so long, but I wanted to get all of the pertinent info out that I could think of. I'm sure y'all will have questions for me that I will do my best to answer... I'm just looking for some help to make our investment worth it and not break the bank on burning propane.
Will will be putting a ceiling in it soon as well as stuffing another 4 1/2" of bat insulation in between the studs before we put the interior walls up. We planned on the floor being the only heating source and we have a 10' big **** fan to help circulate the air in the building.

Thank you sincerely in advance for the help!

Hot_water_fan

Basically, you want as low a water temperature as you can have without the room not meeting the setpoint. As it gets colder outside, you need higher water temps, which is what the outdoor reset is for.  That’s all there is to it on the boiler side. 

To reduce usage once your water temp is low, insulate or adjust the thermostat lower.

GrafixxMan

How long do I give it to see if it'll reach that setpoint or not? Say the garage is at 50* and I want it to be 65*. I have the water temp set at 100* ??? How long should it take to know if that will be enough or not? Then, if it isn't, do I go up 5* at a time, 10*, ____? Also, are you saying that I don't need to mess with all of the infinite settings with the Navien screen?

Hot_water_fan

No, setting up an outdoor reset curve will definitely make your life easier. Just remember: cold outside, warmest water temp. And vice versa. Return temps around 120F and lower are the most efficient. 

Trial and error to find the right temps. Keep the air thermostat at a constant temp: if you want setbacks, this is the wrong type of heat. 

GrafixxMan

Any recommendations on setting up that reset curve?

Sorry for my ignorance, but I don’t even know what setbacks are.

Hot_water_fan

That should all be in the manual. Try 120F for the coldest outdoor temp and 100 for 60F outside and see how it goes. 

Many boilers have a function that increase the temp for every x minutes that the thermostat isn’t satisfied. That’ll lead to some inefficiency, so turn it off or set the duration to a long time.

GroundUp

The install manual is your friend. All the information to set up the ODR is in there, but at the very least you could simply set the water temp to 100* and let it ride for now. It doesn't help that you used the wrong integrator panel for that boiler as well as the wrong pipe size and piping material, but it will work until it doesn't. The main reason you're using so much fuel is because your insulation is terrible. The ceiling should have at least triple what it does, R50+ would be ideal. Also, turn the fan off- that's simply sending your warm air from the floor up to be lost out the poorly insulated ceiling.

GrafixxMan

What’s the matter with the panel and pipe size? I understand about the insulation, but we did what we could afford. Once we put the ceiling up, I plan on putting blown in on top of that.

hot_rod

Looks like maybe you have radiant Pex in the slab, with an oxygen barrier? What tube is that?

But the boiler piping looks like standard plumbing Pex, without a barrier. That should also be heating type pex. Or copper tube

Insulation under and around the slab looks fine. Getting the structure insulated better will cut down the fuel costs.

Curious why a 6” slab? With the tube at the bottom you will need higher supply temperature.
That LEGO panel is quick and easy but puts the tube in the worse spot.

You have a workable system, better than most DIY systems we see. The tweakable components are all above the concrete, that’s a big plus😏 stick with your plan

GrafixxMan

Yes, the pex in the slab is pex-b. I wanted a 6” slab to have a car lift and never have to worry about it being on sturdy enough concrete. I also have a motorcycle lift buried in the slab that’s 7 1/2” tall when it’s collapsed - so you can drive onto it flush with the floor. As far as the boiler piping, yes, unfortunately while I was in the house working, the plumbers ran the tubing to the panel with what they had on the truck. By the time I got out there to check on their progress, they had it all finished up waiting on me to start filling and bleeding it. How bad is it that they used regular pex to go between the two? Is it something that’s going to need to be changed? I can assure you that is the only spot where it’s like that.

I don’t understand how the lego panels put it on the worst spot. They would be in the same spot if they were on flat panels, but without the rebar laying directly on top of them. We did insulate around the outside edge as well with 2.5” flat panels 8” tall. I’m very likely wrong here, but wouldn’t the 6” slab - while taking longer to come up to temp - also work better/longer since the extra surface area will be warmed?

Can anyone give me a rough guesstimate on how much propane I “should” be using? I know that’s a loaded question, but I’d like to have a reasonable idea of how much I should expect to use.

Dave Carpentier

If someone did a proper heat loss calc on the structure , you could get a fairly good idea of how many btu you need per given outside temperature and a suitable boiler outlet temperature.
This would lead to knowing how much input btu (propane) you need.
If someone calculated that, they could also compare the existing plan ceiling insulation vs beefing it up a bunch.. and you could figure if it's a worthwhile investment.
I dont imagine going too crazy on the ceiling would pay off , considering the comparative losses on the adjoining walls, but R30 or 40 would be a realistic guess ?

2400 sqft with 17ft high walls is a huge space, I envy your legroom.

warmAK

Initial start up of 6” slab that size can really draw down some tanks, it should settle out for you 120* water max, 100* water is usually minimum for me (especially in a 6” slab) otherwise I feel your wasting energy pumping fluid around trying to satisfy. as others said set up your outdoor reset set the parameters and it will do it for you.

Hot_water_fan

Can anyone give me a rough guesstimate on how much propane I “should” be using? I know that’s a loaded question, but I’d like to have a reasonable idea of how much I should expect to use.

Nope, not enough details. 

I’d keep the place at a constant indoor temp for a tank and then we can figure your gallons/heating degree days. That’s the best way to estimate. 

GGross

Treat this as an estimate, but plugging in your information and approximate location into loopcad, with 2 10x10 doors

at 10 degree outside air temp (design day for ashland kentucky)
60 degree air temp approx 48,784 BTU/hr 91 f degree supply water temp

72 degree air temp approx 59,911 BTU/hr 110 f supply water temp

Supply water temps may need to be just a tad higher due to the thicker slab

For some reference we have new homes in northern michigan with less heat loss (though this number is not massive by any stretch), so I would expect to use quite a bit of fuel to heat this space. You could take these estimates to get an approximate fuel usage, my guess is that as long as the space is maintaining the correct temperature you are using the correct amount of fuel. Hook up the outdoor reset and set a really good low heating curve, you won't need very hot supply water for most of the year and it will be pretty easy for the slab to overshoot temperatures with higher supply temp than you need (thus wasting fuel, and sacrificing comfort)

Increasing your insulation could lower the heat loss (thus lowering the fuel usage) by 25% or more (R-44 ceiling R-19 walls)

GrafixxMan

I have the ODT hooked up and enabled. It is set for 0* and 65* outside temps and the curve is for a low mass radiant slab. As far as doors go, we have 10x18 and 14x12 insulated doors as well as a 5x7 bar/pass thru type of door. We also have 2 3x5 good windows.

Now, as far as insulation in the ceiling, would blown in be enough on top of the ceiling? I can tell you that neither one of us are going to go up above that and add more in between the trusses. As I mentioned earlier, we have the opportunity to get enough 4-4.5" "leftover" insulation from a friend for free that will do ALL of the walls. We will be taking full advantage of that, but likely won't see any benefits from it until next winter as we have a lot going on currently.

GGross

If you have an opportunity to get free insulation to add to the walls I would start there. Seems like a win-win

Hot_water_fan

I have the ODT hooked up and enabled. It is set for 0* and 65* outside temps and the curve is for a low mass radiant slab. 

Change it to a high mass slab if they have that option. 

hot_rod

You have a few small details working against you at start up. You need to raise the temperature of about 180,000 lbs of concrete, that is the issue with first starts/ high fuel consumption.
The insulation, you already know.

The tube at the bottom will cost you 15 degrees higher water temperature compared to 2- 2-1/2" below the slab. Downward loss goes up a bit also with tube at the bottom. I understand the logistics of getting tube on top of the rebar and raising it up on bar chairs it is a lot of work.

If you plan on bolting equipment down, tube needs to be marked, mapped when you have tube up in the slab. So that also a trade out.

Higher supply temperatures of course cost more fuel.

But at days end, your system will be more fuel efficient than hanging, blower type unit heaters and light years ahead on comfort. Especially in high ceiling buildings.

On big "heat" leak I discovered on my shop 12x12 door is wind blowing in around the edges. I need to detail that better. There are some brush type seals that you can add inside the door for that. Cut down the infiltration losses.

GroundUp

Your combi boiler has an internal circulator. Your integrator panel has an additional primary circulator, which is fighting with the one inside the combi. Your pex is non-barrier as has been mentioned, and your primary loop pex is 3/4" which is too small for proper operation. It should all be 1" oxygen barrier tubing, and the primary circulator on the integrator panel should be removed- but again, it will work until it doesn't. The insulation is the main issue here.

hot_rod

The panel was more than you needed to make the system work. The pump in the boiler and the panel pump are in series, not really fighting🤔
However when the combi goes into DHW mode I think the panel pump dead heads, it doesn’t have a circuit to flow from what I can tell from the exploded view of the DHW pump module in the boiler.

IF the boiler is in DHW mode for long periods that could cause issues with the panel pump, 10 minutes or more perhaps. You could merely un wire the panel pump, just let it spin when the boiler is in heat mode. The boiler pump is adequate to move heat to the panel by itself

Here is one way, if you are up for a repipe to address all theses details. The boiler pipes into a 1” copper header, Navian sells them, but easy to build.
The air purger, circ pump then pipe to the supply manifold Or put the manifolds right on the header and Pex up to them

This fixes the non barrier boiler piping tube issue, and simplifies it to one pump

What you have will work, the 3/4 pex can move 4-5 gpm in that small circuit. So you should be able to get the 48,000 that @GGross ballparked. Especially with the pumps in series🤔

I’m still not clear on the Pex in the slab. B Pex is the type, it comes in plumbing or hydronic versions. The hydronic version has an o2 barrier. It should be printed on the tube what version it is.

If the Pex is non barrier, change the pump to a stainless version, get a extol pro expansion tank and you have a completely non ferrous system, o2 ingress is no longer a concern, nothing to rust or corrode.

Now get busy insulating. My shop in SW Missouri was 1/2 your size, 500 gallons on a cold winter was typical. It had an office that we kept fairly warm, the shop at 60-65