Are my Pressuretrol Time Cycle Numbers Normal?

dlipter

During a steam cycle my pressuretrol cycles from a 0.5psi cut-in to a 1.2psi cut-out.

The cut-in to cut-out time is 2 min.
The cut-out to cut-in time 1 min.

During the heat cycle the burner turns on for 2min to build pressure and turns off for 1 min to allow pressure to drop.
The burner keeps on cycling 2min on and 1min off till the thermostst is satisified.

Do these numbers seem normal?

Thanks

Jamie Hall

Maybe. Unfortunately. The first question, though, is does this cycling start at the beginning of a heating cycle, or does the boiler run for 10 or 15 minutes before it starts?

If it starts right away, your main venting is either non-existent, failed closed, or way way way too small. So... what are your main vents, if any?

If the boiler runs for a while, and most of the radiation is warm, before this starts, what you are seeing is the effect of an oversized boiler -- in this case somewhere between a third and half again as big as it needs to be.

JUGHNE

Do you still have the JB welded boiler?

Have you measured the connected EDR for your replacement?
How does existing boiler compare to your EDR.

dlipter

The boiler does run for 10-15min to build steam. I have a single pipe system with the one main vented with a Big Mouth.

I have not measure the EDR yet. This is the JB Weld Boiler. What kind of up-down timing numbers would indicate a propererly sized boiler?

JUGHNE

I would start with the EDR numbers first as you have the inevitable decision to make in selecting a new boiler.
Your boiler could go beyond any JB repair anytime.
You would not want to make a hasty decision when it is 10 degrees out.
After you crunch numbers and read everything here about the elusive pick up factor to utilize for boiler selection you will be prepared.

How long is your main...assuming it is 2"?

Jamie Hall

A perfectly sized boiler would run for 4 or 5 minutes on and about a minute off (there are those who would argue that a perfectly sized boiler should never turn off -- however, most boilers are slightly oversize -- 10% to 30% -- to account for pipe heating losses early in the cycle -- so-called "pickup factor"). Yours doesn't seem to be too too much oversize, but more than ideal.

dlipter

My main is 2 3/8" OD and 42' long.

dlipter

Is 2 3/8" OD considered a 2" pipe?

Fred

Yes, that is a 2" main and a Big Mouth should be fine based on that length.

gfrbrookline

Given that it is a patched boiler you are just putting good money bad. Save your money and add the new main vents with the new boiler.

ethicalpaul

gfrbrookline said:

Given that it is a patched boiler you are just putting good money bad. Save your money and add the new main vents with the new boiler.

But the main vent will help him now and the new boiler will reuse that return line with the vent on it, so it's actually the opposite of throwing away money, isn't it?

Edit: and to answer the original question, those numbers are about what I see from my ~25% oversized boiler. Maybe mine are a little longer on the fire time.