Steam venting at end of cycle

caseycamire

Hey everyone - I have a puzzler. I bought a house with steam heat last year, and over my first winter, I replaced all main vents and air vents with Gorton vents more or less according to the diagram on the Gorton website. I have yet to insulate the steam lines in my basement, but generally the system now heats up evenly, quickly, and quietly.

During shutdown, however, the radiators at the end of the long steam line (upstairs, front of house) occasionally vent steam, hissing very loudly for about 2-6 minutes, then close again for about 30 seconds, then very obviously draw vacuum, which itself is as quiet as I could expect.

But that steam hissing can be quite loud, and tends to happen more often during my morning temperature ramp up, which is an alarm clock I'd rather not have, since my actual alarm is early enough as it is!

Pressuretroller is set to about 1 psi, but I have never pulled off the pig tail, and my gauge is the 30 psi gauge that I can't really read below 5psi or so.

Could I be overpressurizing? It occurs to me that this could be the pressuretroller tripping the boiler off and not the thermostat, which would explain the steam popping my vents.

Any thoughts on this phenomenon and how to potentially stop it?

ethicalpaul

I want to be sure I have this right. You say “during shutdown...for 2-6 minutes”

Do you mean the first hissing takes place after the burners stop firing?

Regardless, I’d clean the pigtail and install a 0-3 psi gauge but I’m still very curious about the above question

acwagner

It's likely due to the setback and the system actually building pressure. If your thermostat has enough programmable time frames, try recovering from the setback by doing a degree or two per hour instead of all of it at once.

caseycamire

Hey Paul - I'm assuming it's after the burners have stopped firing, since after the hissing stops, about 30 seconds later it always sucks vacuum through the air vent. I will definitely pull the pigtail and source a low psi gauge.

acwagner - good idea. I'm not sure how many phases I can program, but if it's not sufficient, I think I might just leave it at my daytime temp (62F) overnight.

Would insulating the steam lines make a difference? Like if the boiler cycles off, and uninsulated basement lines cool off before the lines running up the walls and under the floors do, could the mains pull vacuum while there's still steam in the upper lines, causing some kind of weird turbulence?

acwagner

Insulating is a good thing to do for a number of reasons, but I still think this particular concern is related to your temperature setback.

Double check that the hissing happens after the burners shut down. I'd be surprised if that's the case. More likely it's the end of the recovery and the boiler is still firing.

How big is your setback? Sounds like you have a nighttime and a daytime setback?

caseycamire

My setback is currently 4 degrees (62 during morning and evenings, 58 when at work and overnight). Is that extreme? I don't have much of a reference point!

ethicalpaul

It's not extreme, but it's enough that it could be making things less optimal. Try narrowing the setback to 2 degrees just for an experiment (62 and 60 let's say)

That is a very cold setting IMO!

mattmia2

Is the radiator with the hissing vent hot all the way across before the hissing begins? Is it venting air or steam?

Maybe it is stuck open and this is just when the system starts building pressure or maybe this is just when the steam starts pushing the air out of this part of the system.

Have you tried switching vents with another radiator?

JUGHNE

You could just set the temp to 62 and hit "hold" for a couple days and see what happens.