Floor Heat 101

[Bubbles Galore]

Alright guys, I need to make sure my floor heat is operating correctly and as efficiently as possible . If I understand correctly:

1. There should be an external temperature sensor that turns on the circulation pump once the temp gets below freezing.
2. The boiler should then fire depending on what the return line temperature is set at.

My question is, how does the boiler know not to fire when the circulation pump is not running? Is there a safety feature that is already built into the boiler to keep this from occuring?

Looking at a different aspect, is there any type of precipitation sensor + a bay input that could be wired into a plc to help necessitate when and if it should come on? I'm trying to mitigate the use of the boiler when its 20 degrees outside but the bays are bone dry...

Thoughts? Opinions? Please share!

 

[Ric]

There is a flow switch on the boiler which will not allow the burner to fire unless it senses flow (circulator pump on). I know you bought the wash so I would check it to see that it has not been bypassed. I've seen that done many times.

 

[mjwalsh]

There is a flow switch on the boiler which will not allow the burner to fire unless it senses flow (circulator pump on). I know you bought the wash so I would check it to see that it has not been bypassed. I've seen that done many times.

Here in North Dakota they have become quite strict in their boiler inspection by the state or a private insurance boiler inspector & the flow switch is one of the items where they make us close a ball valve to see if it is doing its job. Also they make us pop the relief valve.

Bubbles,

From our experience when the cement is bone dry the slab sensor will not drop in temperature nearly as fast ---- that is what would be wired in series to override even if the outdoor temp is calling. 3 stage controllers can be used just as creatively as a PLC. PLCs do have almost unlimited programming & configuration potential but that can be a challenge too without really good information about them flowing.

MJ

 

[JIMT]

We set our floor heat thermostat by using an infrared thermometer to check the temperature of the surface of the bay floors and adjust the thermostat to get the surface temperature between 35 and 40 degrees. Also, adjust the antifreeze flow in each circuit to get an even temperature across the bays.

JimT

 

[Bubbles Galore]

Well I was able to get the circulator pump wired into the thermostat that Eric H recommended with the +/- 1 degree variance. Now I just need to get the sensing bulb attached to the return line and we should be good to go. What do you guys recommend for insulating the bulb when attached to the return line so that I don't get a false reading from the ambient air in the equipment room?

 

[mjwalsh]

Well I was able to get the circulator pump wired into the thermostat that Eric H recommended with the +/- 1 degree variance. Now I just need to get the sensing bulb attached to the return line and we should be good to go. What do you guys recommend for insulating the bulb when attached to the return line so that I don't get a false reading from the ambient air in the equipment room?

Bubbles - John,

For our thermistors & RTD thermocouples on new piping we put in tees with solder & with center threads to screw in a threaded sensor. This makes the sensor right in the flow which is the ideal. On existing pipe we used some special conductive grease we got from a local Trane Service Person to conduct better where the pipe with a non threaded sensor attach to each other. We secured the sensor with some electrical tape around the pipe & then covered both pipe & the sensor with fiberglass pipe insulation. This approach has worked good for us over the years.

MJ

 

[Bubbles Galore]

I finally have the floor heat up and running properly with a Honeywell aquastat zip tied and insulated to the return line...depending on wind and such I have the return line temp set between 55 and 60. I am still using an Intermatic timer to shut the system down between 9p and 630a and it appears as though it is working well. I guess the gas bill will tell the true story...

Anyway, would a different type of thermostat be a better fit for the return line or should I just stick with the Honeywell? All in all I hope this will be a much more efficient system than what I had with the single bulb slabstat.