Boiler Temp on/off

[nate379]

I went to turn my boiler up for winter and I can't remember what the max is supposed to be at.

I want to say 170 or 180.

Radiant floor heat.

Also what is the norm pressure on the system? I have 10psi right now but I have seen other setups at 20psi. My T&P valve is 30psi, no temp listed on it though.

Google searching isn't coming up with much.

 

[tcianci]

Nate, not too familiar with radiant but with FHW radiation, about 180 is the norm. It really comes down to how fast you need the system to react, or let me re-phrase that since we would like them to react instantly... the hotter the boiler water, the more quickly you can reach the desired room temperature. Your 10psi will go up when you increase the temperature setting. The 30 psi relief valve is just that, a max pressure and temperature safety device. Lots of FHW systems run about 10 to 20 lbs.

 

[ixlr8]

Most radiant floor heating systems temper the water down to 110dF or less before entering the tubing. You might not need to raise the temp at all. My system needs the water to be at 95dF to have a floor temp of 82dF to provide the BTU's I need to heat the house.

 

[walrus]

I went to turn my boiler up for winter and I can't remember what the max is supposed to be at.

I want to say 170 or 180.

Radiant floor heat.

Also what is the norm pressure on the system? I have 10psi right now but I have seen other setups at 20psi. My T&P valve is 30psi, no temp listed on it though.

Google searching isn't coming up with much.

What kind of radiant floor, in concrete or under wood?, I don't see how you'd want 180 degree in concrete so must be wood. In that case whatever takes to keep you warm, the lower the temp though the better the energy savings

 

[nate379]

Concrete. I have a mixing valve that mixes the outbound and inbound water so right now with the boiler at 170* it is 120* out at the boiler and 100* coming back in.

My domestic hot water is heated by the boiler as well. I turned it down to 140* (lowest the boiler goes) this summer since I just needed it for the domestic hot water. I forgot to write down what the winter setting was though. (oops)

I might just call the heating guys to do a yearly check on the system to dial everything in, it's only $40 or 50.

 

[JCByrd24]

Anywhere from 165-185 is where you want to be for boiler temp. Sounds like your're running just fine but could go up a bit if you thought you needed to.

 

[tcianci]

I only have experience form older systems but I know older controls that use the boiler for heat and DHW have a control that has a high limit, a low limit and a differential control. When the source calling for the boiler to fire is a heat zone, the boiler temperature cycles between the high limit and the differential set point. For example if your high limit is set at 180 and your differentail is 15 degrees, the boiler water will cycle between 165 and 180. When the source that calls for the boiler to fire is the thermostat on the hot water coil, the boiler cycles between the low limit and the diferential. If your system was designed correctly, with the proper controls you shouldn't need to change any settings between summer and winter or for your DHW.

Now that I think about it, up where you are...do you even have a summer and winter?

 

[HoosierBuddy]

Are you using any PEX in your system?

IIRC, my PEX is rated at 180 degrees F. The lower the temperature you can run your water at, the higher the efficiency of the system. As others have said, the pex in concrete should work well at a lower temperature.

I've had problems with the 2 zones on my system where I have pex clipped up under the subfloor between the floor joists. I actually went though mine about a month ago and reconfigured the tubing to get more loops and use aluminum sheets that clip around the pex to try to get more heat sucked out of the pex at a lower temperature.

The issue I've had is the water from those zones comes back to the boiler at almost the same temperature it leaves the boiler...meaning not enough of the heat has flowed into the heated space. Then...the only fix is to crank up the boiler temperature to force more heat in.

I'm hoping I'll see a better outcome with twice the tubing in the joist space, aluminum plates tieing the tubing to the subfloor and an additional layer of FBF insulation (added to the 6" of fiberglass I had) across the bottom of the joists to add to R-value and eliminate thermal bridging between the joists and the unheated crawlspace.

My system runs about 10 psi...so that doesn't sound too far off.

Phil

 

[nate379]

Of course there is summer. Was almost 90* this summer.

I only have experience form older systems but I know older controls that use the boiler for heat and DHW have a control that has a high limit, a low limit and a differential control. When the source calling for the boiler to fire is a heat zone, the boiler temperature cycles between the high limit and the differential set point. For example if your high limit is set at 180 and your differentail is 15 degrees, the boiler water will cycle between 165 and 180. When the source that calls for the boiler to fire is the thermostat on the hot water coil, the boiler cycles between the low limit and the diferential. If your system was designed correctly, with the proper controls you shouldn't need to change any settings between summer and winter or for your DHW.

Now that I think about it, up where you are...do you even have a summer and winter?

 

[TurnipTruck]

With my radiant heated shop, I run the boiler at about 170, the mixer is 110, and the boiler return I try to keep at least 120, but that doesn't happen for the first hour of firing each day. That is with a constant (uncontrolled) bleed to keep some heat in the return.