How low is too low for return water temp.

ricking

Got cold enough lately for the boiler to run almost full time. Mid to low 20's and that is below normal. Radiant heat in ceiling with electric boiler. One zone. Did the refit on the boiler myself with excellent help from this site. All seems to be running fine. Just a little slower to heat house from 65 to 69 with colder temps. Supply temp is set at 115. The return water ranges from 80 to 85. Thats a nice spread but is it too low return temp. Not sure what the circulator is circulating in GPM but do those numbers sound ok?

hot_rod

does the boiler ever cycle off or does it run non stop?

if the boiler cycles off, you probably have enough "horsepower" A load calc could help confirm that.

Is it a multi speed circ pump? What speed? Kick it up if you can, lower ∆T will increase average surface temperature of the panel, and increase output.

ricking

Pretty sure it does cycle off. It's a 3 stage boiler 34k per stage. Have'nt seen all 3 on. Maybe at start up to heat up the cool water. When water is up to temp on outlet, it runs mostly on 1st stage and that will turn off once and a while. One speed pump. There is no problem with the house not being warm. It is a very even heat through out the house. My thoughts were maybe if the return was higher, boiler would cycle off more saving costs. But. Heat transfer is heat transfer. Right? If it takes x number of BTU's to go up 1 degree.....

hot_rod

Ideally, the less a boiler, any mechanical component cycles the longer it will last and.

in a perfect world heating equipment would cycle on and continuously modulate to the load, little if any cycling.

If the home is comfortable, it sounds like you are good to go.

BTU in vs BTU out

Ceiling heat is not a ∆T sensitive as a floor panel would be. With floors 10- 15° is often a design ∆. As long as you are not walking on the ceiling, that surface temperature is not as critical.
Cover the load with the lowest SWT, that is the goal of outdoor reset controls, and pursues best operating efficiency..

Harvey Ramer

Did I read correctly... 34kw per stage?

ricking

Sorry Harvey. Forgot the BTU after 34K. Its a 30kw boiler total. 6 -5k elements that stage 2 at a time. Total 102,360 btu.

"As long as you are not walking on the ceiling, that surface temperature is not as critical."

Those days are long over Bob. Thanks goodness.

Paul48

Do your neighbors lights dim when the boiler kicks on? Man.....My electric bill would kill me.

ratio

Oh, oh, oh—how 'bout an SCR on one stage? I'm pretty sure with a Honeywell T775 to control it you could get 99% turndown on that boiler!

Zman

In a perfect world it would be nice to get your delta t less than 20, just to even out the radiant temps. The bottom line is comfort.
I agree with the outdoor reset recommendation.

Gordy

The return temp for that boiler is fine.

Do you use setbacks?
Is this system zoned?
Is the supply temp actually reading 112*?

27 degree delta is pretty wide I think you would experience better comfort with a 15 delta. But if your happy that works then.

Harvey Ramer

I have a feeling you will NEVER see it on the third stage. I might be tempted to disconnect one of the 5K elements from each stage, to give the boiler better temp control of the supply temp with less stress on your electrical system.