In floor radiant heat programmable thermostat

[jblnut]

I currently have a Tekmar 519 thermostat in my shop that runs the radiant in floor heat. I have a floor stat installed and don’t really utilize it night now. I’d like to find a decent programmable thermostat that works with a floor stat so I can set it 1-2f warmer during the day and back down at night. It doesn’t need to be a WiFi connected stat.

This is NOT due to working temp comfort or whatever you want to call it…… I have an outdoor wood boiler that isn’t struggling in anyway to keep up at night but it’d be nice if I could put a smaller load in at night and then small loads during the day as needed so it could be more efficient. I have a lot more crappy wood than I do nice oak and it loses a lot of efficiency when it’s loaded full full.

I can stoke it during the day while I’m home and set it to cool off at 10pm so the heat won’t kick on until morning sometime. I’ve been doing this manually for a few weeks now and it works great so if it could be automated that’d be great lol

Thank you in advance.

 

[Firebrick43]

Honeywell T6?

Supply house.com T6

 

[jack stand]

How well is your shop (and slab) insulated?
In my thinking, if its well insulated, you might extend your burn. If not so well and you loose those 1 or 2 degrees in an hour or two of "coasting" you've really not gained much except for buying an expensive t-stat that I don't think exists anyway.
I don't think you'll find a t-stat with accommodations for a slab sensor that's not for a radiant system. It's widely accepted that you don't do these small setbacks with radiant heating regardless of your intentions (saving wood).
Have you thought of better wood (fuels) for the overnight?
I sympathize with your situation as I heat radiant and a wood boiler also but I have an indoor boiler and if necessary, feeding it at 2am is a whole different "event".

 

[jblnut]

Honeywell T6?

Supply house.com T6

That will do the trick I think. We have a Honeywell thermostat in the house for the forced air that looks just like that and it seems to work great.

How well is your shop (and slab) insulated?
In my thinking, if its well insulated, you might extend your burn. If not so well and you loose those 1 or 2 degrees in an hour or two of "coasting" you've really not gained much except for buying an expensive t-stat that I don't think exists anyway.
I don't think you'll find a t-stat with accommodations for a slab sensor that's not for a radiant system. It's widely accepted that you don't do these small setbacks with radiant heating regardless of your intentions (saving wood).
Have you thought of better wood (fuels) for the overnight?
I sympathize with your situation as I heat radiant and a wood boiler also but I have an indoor boiler and if necessary, feeding it at 2am is a whole different "event".

The shop is 54x72x18 and is very well insulated. Slab has 2” foam down 3’, 4” foam around the outside 8’ and 2” of foam in the middle area. Walls are 8” thick blankets between poles. There is blue foam between all wall girts on the West and North sides where the wind hits with an enclosed lean-to on the entire South wall. Not sure of R value in attic but there is 28” of pink blown stuff up there.

In floor loops are all 250’ runs and are 8” apart over the 4” foam and 12-14” apart the rest of the building.

I’ve been making the setbacks manually the last few weeks and it’s been working very well. When we have family events in the shop I can turn the stat from 58f up to 70f air temp and it’ll be there in less than 12hrs.

I know exactly when the heat runs as I have an InkBird WiFi grill monitor on the back of the stove to monitor supply/return temps and it’s been showing that the shop won’t call for heat until 5-6am when I set it back 2f at 10pm. It calls for heat around 2am when I set it back 1f. It’ll be back up those 2 degrees before 10am when I set it back up around 7:15am.

When the stove is full full of even crappy poplar and it’s -25f and windy it’ll go from 10pm-7am without a refill. Spending some $$$$ to ease the load on the wood use is okay in my book. I’ll likely never recoup the $$$$ I have invested in the entire system anyway so what’s another couple hundred lol.

EDIT: if you have WiFi near the stove you should really look into an InkBird BBQ thermostat. It’s amazing to be able to check things from your phone !!

Orange/ red are house
Green/blue are shop

 

[jack stand]

Sounds like a very nice installation and building.

 

[jblnut]

Sounds like a very nice installation and building.

Thank you !! I took the advice of oh so many on here and put more insulation in than I, or my builder, or the lumberyard, or the insulation guys, thought I needed. I told them I wanted it insulated like I was in Antarctica so it’d heat with a candle and a fart and cool with a fan blowing over an ice cube. I cool the whole shop with a single 6k btu window AC. It truly is bonkers.

I ordered that Honeywell stat and will update on how it does !!

Thank you for the replies.

 

[Mr onetwo]

This is an interesting case.I have never been a believer in setbacks with radiant floor systems, but I look forward to seeing how this works out.

 

[jblnut]

This is an interesting case.I have never been a believer in setbacks with radiant floor systems, but I look forward to seeing how this works out.

Comfort setbacks are impractical with in floor but this has been doing what I want it to do so far. I’m excited to automate it !!

 

[jblnut]

Update


I installed the Honeywell thermostat linked above that utilizes both my air and floor stats and have the shop heat up to 58f during the day and cool off to 56f over night. The load on the stove is way less (proven with a temp/run time monitor on the stove) and it’s great. The shop calls for heat and gives the stove a workout around 8am once the sun is up and when I’ve already been out there to reload it. It’ll burn hot and hard until 10am and maintain temp until 9pm and won’t call for heat until midnight usually.

It’s good to let the stove stretch its legs and burn the **** out of the flue and I have noticed a definite decrease in the amount of wood used overnight. Honestly I bet I gained at least 2hrs of run time before it “has” to be loaded again.

 

[jack stand]

I wish that I had built in 1000 gallons of storage into my wood boiler/radiant system. You mentioned letting your boiler "stretch its legs", I've heard and been told this by many boilermen over the years that a boiler running "flat out" is at its best and very happy along with maximum efficiency.
Using a very variable fuel (wood) is another challenge that's added to the whole operation and the cycling that occurs when heat is called for is not as simple as it is with conventional fuels.
"Batch burning " to charge a 1000g of storage in 3-4....?
hours and having that last for days (depending on the heat loads) would be nice. I just didn't have, or want to surrender the Sq footage of otherwise useful space for this.
Sounds like you're new t-stat is a success.

Ps, I love my radiant system and the wood boiler, and the above is not a complaint at all.

 

[Mr onetwo]

Professor **** Hill