Looking for a thermostat for floor heater

[slash007]

I have it set for the circ pump to kick on around 32-34 degrees then the boiler to kick on around 30. I just figured I needed the circ pump to be on first, but that was the extent of my thinking as I really had no idea how it all works. What temp would I set it on if I attached the sensor to the plumbing? Would it matter if it is pvc and not copper?

I would love to stop by sometime, will keep it in mind.

 

[GoBuckeyes]

2Biz I definitely owe you a few beers. I just saw post #35 & #36! I'm sorry for keeping you up at night. As for your question, I have not looked at any other heaters. I did just look at some of the pump data and I was thinking that with two Takagis in series I would need 50 head ft to get the flow through the heaters but 16 gpm total (8 gpm each). I found a Taco 2400-50 will flow 15gpm at 46 head ft using a 1/2 hp motor. It's about a $500 pump/motor setup.

 

[2Biz]

I have it set for the circ pump to kick on around 32-34 degrees then the boiler to kick on around 30. I just figured I needed the circ pump to be on first, but that was the extent of my thinking as I really had no idea how it all works. What temp would I set it on if I attached the sensor to the plumbing? Would it matter if it is pvc and not copper?

I would love to stop by sometime, will keep it in mind.

Slash...You want your circulator to kick on at 32° like you have it set based on outside air temperature since you don't have a slab stat. You could actually have it kick on at a lower temp, but you'd have to experiment with it. Mine comes on at 32° only because I have multiple systems running off the secondary output on the weepmizer....

What you have to do from there is to wire the t-stat to the boiler so it picks up the line (Hot wire) from the circulator. This will "Only" allow the boiler to fire if there is power to the circulator. You DON"T want a situation where the boiler can fire without the circulator running. You currently have this possiblity. If you put the boiler t-stat sensor on the return bay loop pipe, Then the boiler will cycle on/off based on return glycol temp. The boiler t-stat has to have differential capability. Not all t-stats are the same. I have mine set with 10° differential. The boiler kicks on at 60° and off @ 70°. This gives me an average of 15 minutes on - 15 minute off to complete the cycle. Even though you are picking up heat through the PVC pipe, it will be consistant. So you may have toplay with the diffential and setpoint of the boiler t-stat to get it dialed in. But once you have it set, it will repeat.

When the outside temp goes above 32°, it cuts power to the circulator which in turn cuts power to the boiler t-stat thus shutting the whole system down...

2Biz I definitely owe you a few beers. I just saw post #35 & #36! I'm sorry for keeping you up at night. As for your question, I have not looked at any other heaters. I did just look at some of the pump data and I was thinking that with two Takagis in series I would need 50 head ft to get the flow through the heaters but 16 gpm total (8 gpm each). I found a Taco 2400-50 will flow 15gpm at 46 head ft using a 1/2 hp motor. It's about a $500 pump/motor setup.

I wished I would have seen this circulator before putting (2) 013's in series. This is a much better pump to handle the job.... It only uses an amp more than mine put together. Maybe I was looking at the ability to rebuild the 000 circulators with just a cartridge. I don't believe you can do that with the 2400 series. I'm sure its no biggy. What a learning curve all this is!

 

[2Biz]

After digesting this more....46 feet of head only yeilds 20 psi. Are you sure this is enough? Now you'll have to revert to the demand heater data. I believe it takes roughly 25 psi to get the full output of the heater. MAybe this is why I went with the two 013's after all. (2) 013's are rated at 28 feet of head each or 56 feet of head combined at 8 gpm. Neither may work for a dual demand heater system like your needing.

I found some actual wall hung boilers that only have 2-3 psi restrictions through the boiler. You may have to look into one or two of these. Problem is, when they are listed as a "Boiler" the price goes way up....

 

[mjwalsh]

This will "Only" allow the boiler to fire if there is power to the circulator. You DON"T want a situation where the boiler can fire without the circulator running. You currently have this possiblity.

2Biz & others,

It seems like a flow switch to prove actual minimum needed GPM flow would make the system more fail safe against a low or no flow situation. I know our boiler inspector makes sure that there is a flow switch & that it is working every time he stops by to inspect. Some boilers of course are more vulnerable than others. Here is an example of a 1" size flow switch:
http://www.pexsupply.com/Mcdonnell-Miller-114410-FS4-3Z-1-Flow-Switch-w-ANSI-terminal-connections

mike walsh king koin USA

 

[slash007]

So at least my thermostat for the circ pump is correct Thanks for the explanation, that is exactly what I was looking for. Now I just need to make sure that I wire it correctly, hopefully before the crazy cold hits on Friday. I will take a pic of my boiler thermostat and see if it is the right one. If you look at the picture I posted, it says all over the boiler "pump on first". The previous owner wrote that on there as a reminder. I once had someone turn the boiler on without turning the circ pump and after losing my mind I checked the unit and it still seemed to work. I contacted the previous owner and if I remember he said that it happened to him once so he had it wired so that the boiler wouldn't fire unless the circ pump was on. I'll have to check the wires to be sure though. If it is already wired like that, then I could just setup the probe of the boiler stat and I should be good to go? What I did now was to just connect the boiler stat inline with the on/off switch of the boiler.

 

[2Biz]

I will take a pic of my boiler thermostat and see if it is the right one.

Its easy to tell. Take the cover off and see if it has more than one dial. You'll have the main temp dial and another tucked in behind the switch if it has differential. The differential dial isn't visable with the cover on. At least thats how mine is. Mine has up to 30° differential.

Another good point Mike..I hadn't got that far. I was trying to make sure slash corrected the wiring with his t-stats before going further. My old system had a flow switch like you linked to. I didn't think I needed one tll now since the heater has one built in. But I can see now if the main circulator quits the boiler circulators can continue to run. It might be something I need to correct.

 

[slash007]

What you have to do from there is to wire the t-stat to the boiler so it picks up the line (Hot wire) from the circulator. This will "Only" allow the boiler to fire if there is power to the circulator. You DON"T want a situation where the boiler can fire without the circulator running. You currently have this possiblity. If you put the boiler t-stat sensor on the return bay loop pipe, Then the boiler will cycle on/off based on return glycol temp. The boiler t-stat has to have differential capability. Not all t-stats are the same. I have mine set with 10° differential. The boiler kicks on at 60° and off @ 70°. This gives me an average of 15 minutes on - 15 minute off to complete the cycle. Even though you are picking up heat through the PVC pipe, it will be consistant. So you may have toplay with the diffential and setpoint of the boiler t-stat to get it dialed in. But once you have it set, it will repeat.

When the outside temp goes above 32°, it cuts power to the circulator which in turn cuts power to the boiler t-stat thus shutting the whole system down...

I am pretty sure it is already wired to only kick on with the circ pump on, but still need to verify that. In case it isn't, do I need a relay to do that? I unhooked my stat today and plan on taping it to the return line tomorrow. According to the instructions with the stat, it can be set to a differential, but I don't see the second set point. I'll remove the knob and see it it is under there. So basically I need the temp to be around 60-70 degrees in order to be effective?

 

[2Biz]

Can you get a model # off the T-stat? Most of the ones we use have a 30a rating, so no need for a relay. On my t-stat with a differential dial, you have to remove the cover to see it. It sits between the switching mechanism and the rear of the housing. Here is the one I use:

http://www.pexsupply.com/Honeywell-...5-200F-range-5-30F-Adj-Differential-1738000-p

I guess we need to call them by their real name...Aquastat instead of T-Stat....You won't find them if you search for thermostat...

Even though it has a range from 65°-200°, I set mine a little below 65° and it gives the system a range from 60°-70° on/off...Its the closest one I could find to give me the range I needed.

There are a lot of factors that make every system different. I didn't get the settings correct right out of the gate. You might have to play with your settings a little. I try to maintain between 35°-40° slab surface temp (I use a hand held infra red surface temp sensor). 60°-70° on the return Aquastat gets me there. Yours may be different, but 60-70° should be a very good starting point. Its not hard to dial in once your system stabilizes. Its amazing how consistent it is once you get it there...

 

[cantbreak80]

Or, this one...although, it works best in an immersion well.

http://www.pexsupply.com/Johnson-Co...age-Digital-Temperature-Control-120-240v-SPDT

I use a hand held infra red surface temp sensor

For more accurate readings, wrap the surface with non-reflective black tape...like the stuff used on hockey sticks or baseball bats.

 

[slash007]

For more accurate readings, wrap the surface with non-reflective black tape...like the stuff used on hockey sticks or baseball bats.

Are you talking about wrapping the pvc with non-reflective tape before mounting the stat, or talking about measuring surface temp like 2biz was referring to?

 

[2Biz]

Are you talking about wrapping the pvc with non-reflective tape before mounting the stat, or talking about measuring surface temp like 2biz was referring to?

I use the hand held infra red surface temp sensor to check the concrete surface temperature so I know how much I need to change the aquastat on the return line from the bays...If it was 20° outside and the surface temperature of the slab was 50°, that tells me I could possibly dial my return line aquastat down about 15°...Make sense?

CB80...Good find, I just bought one of those to cycle on/off the heat exchanger pump for my new hot water float tank. I was trying to see if Slash had the one I linked to since his is the dial type. I didn't see the A419 when I was putting my Floor heat system together or I would have bought it instead. I like the thoughts of dialing in temps to the exact degree. The dial type takes some tinkering with.

 

[slash007]

View attachment 540 View attachment 541

Here are pics of my thermostat...

 

[2Biz]

I d/loaded the manual for this aquastat. Isn't there a lever to the right side if the switch between the switch and the metal back plate? Is there a scale marked on the back plate? I tried blowing your picture up, but its too low of a resolution. But according to the manual, it has a lever that adjusts the differential on the right side. Without being able to read the markings on the plate, its hard to tell from the picture...

 

[slash007]

If you look at the stat pic, right next to the screw in the middle there is a lever to the right. It sits right under a marking that says "min" then you can slide it up to near the dial where a marking says "max". I saw that but wasn't really sure how it would work as there are no #'s involved.

 

[2Biz]

Whoa! Your guess is as good as mine! No markings? I wonder? Max or minimum of what starting values? You could put it on Min to see what the on/off cycle was then max to see what that on/off cycle yielded. Then you'd at least know what direction to go. Or you could get a better one so there is less guessing. The manual doesn't tell how to adjust it, only that the differential is adjustable.

 

[cantbreak80]

Are you talking about wrapping the pvc with non-reflective tape before mounting the stat, or talking about measuring surface temp like 2biz was referring to?

I thought 2Biz was reading copper pipe temperatures. The infrared thermometers give inaccurate readings when directed at "reflective" surfaces like copper pipe and brass fittings. Something I learned in "plumbing for dummies school".

I just bought one of those to cycle on/off the heat exchanger pump for my new hot water float tank.

I have one installed on my boiler/rinse tank. I sealed the probe inside a piece of poly tubing and submerged it inside the open water tank. Along with a timer, it serves as a setback control for the boiler...110F during normal business hours...70F from 10pm to 6am.

 

[2Biz]

I used the Infra red thermometer last week to check slab temps. You could actually tell where the lines were in the floor. The readings averaged between 35° and 40° throughout each bay. If I moved out of the bay 1 foot, the surface temp measured 15°. It had got down to less than 15° the night before. So it seems to give accurate readings pointing it at concrete.

I'm going a different route with my hot water float tank since the new HTP Water Heater has additional 1" ports for different types of heating. I read where you don't want to submerge the probe directly in water because it won't last long. Sealing the probe in poly tubing was a good idea. I'm having my float tank made with an additional 1/2" port for a well to put the probe in. Good Idea on the setback control...I never have any business between 10pm and 6am either.

 

[slash007]

I actually have another new aquastat that I will pull out and post a picture. I got it first, but wasn't able to use it because it only had two screw so the boiler would kick on at the opposite of what I wanted. For example, if I used it on the circ pump it would kick off at 32 degrees instead of on. Maybe it will work for a differential though.

 

[slash007]

View attachment 542

Here is a pic of the other stat I have. Not sure of the exact model as I don't have the box, but I have the instructions and they are under it. It is a White-Rogers Brand though.