How to test a pressuretrol

Jeff_44

How would I go about testing the pressuretrol on my one pipe system?

BobC

Test pressuretrol

  The picture below shows the inside of the pressuretrol, the brown

object is a microswitch. The two brass screws are the contacts of that

switch, Normally the contacts of this switch are closed until pressure

builds enough to trip it off. If you have a meter (With the boiler power switched off at the

circuit breaker panel), you should measure zero ohms across those two

brass screws. You can force that silver arm up and down (1/16 to 1/8")

to mimic the action of the internal bellows, when you do you will hear a

small click and the reading should go up to hundreds or thousands of ohms.

Let it move back and the reading should go back to zero ohms.



All that does is tell you that the switch works it does not tell you if the pressure bellows is good or if the pigtail is clear.



With the power back on you can manipulate the silver lever and should be

able to turn the burner off and on, assuming the thermostat is calling

for heat. Just be careful so you don't get a shock, those screws are

carrying 120v. Again this tells you the switch is good it does not tell you if the bellows is good or the pigtail is clear.



One problem pressuretrols have is they are not accurate so just because it's set to 2 PSI does not mean the trip point will be 2 PSI. Sometimes they get flaky at very low settings where they trip off but won't reset when pressure goes back down.



Bob

norb

another question regarding Pressuretrol

I have a Honeywell ( additive) due to the "cut-in" labeling on the outside where the main scale slide is located.

My Question, just to make sure I am understanding how the pressuretrol and the guage ( 0--30psi ) should be working:

     If I set the "cut-in" to 1/2 and on the inside of the pressuretrol I then set the "Differetial" to . let's say' 3 1/2, then is 4 the PSI reading I should have on the guage when the furnace starts to run, based on the call for heat?  Is this correct?

If this thinking is not right, would you explain to me how those settings should work?  My guage needle does not move from the zero ( or I should say one psi marker on the guage).   If my psi should be 4 on the gauge but the guage does not move, is the guage faulty or the piping blocked around the gauge?

Enreynolds

Pressuretrol

The cut-in is the pressure that the system will have to lower to after the pressuretrol breaks on pressure, so 1/2 psi or lower is the pressure that should be showing on the gauge at start.  With an additive differential, the internal setting is the amount of pressure above the cut-in pressure the system will allow before breaking on pressure.  Note:  4psi cut out is WAY too high for residential heating.  (Almost) All residential steam heating systems installed after the early 1900s were required to run under 2psi, with rare exceptions.  If you are running at 4psi you probably have other problems with the system and are wasting a lot of money on fuel.  Post pictures of your system so the wall can help.

Eric