Pressuretrol question for pressure settings

melo

Hi all, this is a photo of my parents pressuretrol setting. We had a boiler guy and this is the setting he had set a year or so ago because the boiler was short cycling due to it being oversized and us not having too many radiators.

We tried installing bigger radiators, which helped a little bit but I am wondering if I'm understanding the pressuretrol correctly.

Based on this pressuretrol, the boiler will go up to 6 PSI because the main is 3 PSI and the DIFF is at 3 PSI. So the boiler will go to 6 PSI then the pressuretrol will shut it off for the boiler to come down in pressure and when it goes back to 3 PSI, the boiler will kick back on until it hits 6 PSI.

Is that correct? If so, in order to help alleviate the short cycling, would it be smarter to make the main 1 PSI and keep the DIFF to say 4 PSI? So the boiler will climp to 5 PSI (4+1) then turn off, as the pressure goes down to 1 PSI, it will start back on?

Neild5

Your pressurtol shows the DIFF as subtractive, so the pressure will build to between 3 and 4 and shut off, drop 3 psi and restart, and repeat until the thermostat is satisfied.

melo

Interesting, maybe the pressure gauge is off/defective? I clearly seen the gauge go up to 6 then turn off, the pressure guage come down before the boiler kicked back up.

melo

There is a photo of the gauge on the left side, that's pretty much where it turns off, right almost at that line as the vent closes and the boiler shuts off.

Jamie Hall

@Neild5 is correct — that is a subtractive pressuretrol. Now that it may or may not be that accurate. However, that pressure gauge, while required by your insurance and building codes, is not likely to be even as accurate. To really find out what your system is doing, you need to add a 0 to 3 psig gauge. It can go on the same pigtail with a little ingenuity. You also need to be sure that the pigtail is really clear all the way into the boiler. They do clog…

Waher

The pressurtrol should not be set to operate above 2 PSI. Ideally it will be set to cut out at 1.5 PSI. Over 2 PSI is creating problems.

The scale on the right should be set under the 2 line and the scale on the left at 1.

melo

I ended up replacing the pigtail, old one looked a little clogged