Looking for a better understanding...

John Shea

Is this correct?

Even though you may have a systems pressure control set high, the system may still run at a very low pressure?

Example:

My one-pipe system at home will easily heat the house from say 66 F -69 F without the burner cutting out. It's got an old White-Rodgers pressuretrol that won't allow settings below 1lb. (can't find any doc. on the control, so I don't know if that's cut-in or cut-out pressure)

What physically effects the pressure? length of cycle? is the boiler making steam faster than the system can condense it? ... that gets me thinkin that that would be the case. My boiler is currently undersized... would that mean that it would never build up too much pressure?

Thanks for sharing your thoughts.

Al Letellier

pressure

Think vents. When the boiler makes steam, water changes to vapor and expands 1700 time in volume, giving steam velocity and pushin air out of the system thru the pipes and radiators. When the air is all out and the vents close, pressure builds in the system until the heat demand is met or the pressure switch opens and stops the burner. In the latter case, when the systmen cools, the pressure drops and the switch closes, restarting the burner. This process continues until the call for heat is satisfied.
If your boiler runs all the time during a call for heat, the switch may be bad or the pigtail is plugged. If your boiler is too small for the load, it will run forever and you will never heat the house on the colder days.

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Al Letellier

pressure

Think vents. When the boiler makes steam, water changes to vapor and expands 1700 time in volume, giving steam velocity and pushin air out of the system thru the pipes and radiators. When the air is all out and the vents close, pressure builds in the system until the heat demand is met or the pressure switch opens and stops the burner. In the latter case, when the systmen cools, the pressure drops and the switch closes, restarting the burner. This process continues until the call for heat is satisfied.
If your boiler runs all the time during a call for heat, the switch may be bad or the pigtail is plugged. If your boiler is too small for the load, it will run forever and you will never heat the house on the colder days.

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jim post

Hot water pressure

Does the pressure of a hot water system affect the cycle time of the boiler. I mistakenly added water to my system the other night. Now the pressure goes over the desired setting (22psi) and the boiler seems to short cycle. Before the boiler system temp would range from 170 down to about 130 before the boiler kicked back on. Now it doesn't get much below 160 before it refires. Should I bleed the pressure back down to the desired setting. Thanks for educating me.

[Deleted User]

The W/R

Pressure Control has 2 settings. The front dial setting is the cut in. Remove the cover. There you will find the differential setting. Add both for the cut out.

[Deleted User]

If that gage

reading is correct, shut the boiler down. Get a professional ASAP. 30# is the max rating for most residential boilers. You should have wet feet.

John Shea

that clarifies things a bit.

One more question, though.

Does that mean that a moderately undersized boiler will never build much pressure under normal operating conditions?

Thank you.

Dave Bush

Absolutely.

Yikes.

That's bad.

John Shea

isn't it odd then...

that the W/R control won't allow you to cut-in at anything under a pound?

It looks like maybe if you had a special driver, you could remove or relocate the 'stop' for the cut-in. Would this be advisable?

oil-2-4-6-gas

.

you have "red lined" your boiler like a kid driving a Honda ///////////shut it down and verify the pressure with an accurate gage,call a pro make sure the gage is good and relif valve operational

Mad Dog

Yes, an undersized boiler will run a marathon

and not top off on pressure....and as Al said, vents affect pressure cyling greatly..also boiler size. Mad Dog

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