Change Boiler Return Protection Valve From 130 to 140?

velvetfoot said:

It's the time of year to make changes and I've been thinking about this for a while.

It's on a pellet boiler with a 120 gallon tank. Baseboard convectors.

Everything works fine now at 130, no creosote, etc, but I wonder if 140 would provide any operational advantage? I have the cartridge already and have a tendency to not leave well enough alone.

I'm thinking a greater volume would recirculate through the boiler but higher temp supply through the baseboards would be good. Water coming out of the boiler to distribution would always be at least 150 or so. Excess goes to buffer tank, as usual.

It would take a little longer to heat up and then less volume would be available, while things heat up, I imagine.

Thoughts?

Click to expand...

I started with a 130 on mind and went down to a lower temperature, here is why.

There is a differential in the thermostatic cartridge. On the Caleffi brand it is around 18°. So the 130° cartridges closes off the bypass port completely at 148°. At that temperature condition, 100% of the boiler output goes to the load.

On my EKO 40 the blower starts to ramp down at about that same temperature. Granted it is an early Euro version control, I know some have tweaked the with resistors add to the sensor.
So basically my boiler was reving down just when my bypass closed and I wanted full boiler output going into the system.

Maybe check if or when your control starts modulating down the firing rate, if it is the same as mine the higher temperature sensor may be taking you in the wrong direction.

I think I went with the 120°. So at 138° is has closed the bypass completely, just about the exact temperature I need for my boiler return temperature.

The higher temperature sensor may work better on a boiler that doesn't modulate, or modulates at higher temperature.

Regardless you want the boiler to start adding BTU to the system ASAP, as long as it is protecting itself from cold return.

Remember also, its the distribution, or load that drives the operating condition of the boiler. If the heat emitters or loads are matched closely to the BTU output of the boiler, it will find and operate at thermal equilibrium.