Pressure relief valve non-stop hissing

rhodebump

Hi,

Stopped by the building tonight, and the pressure relief value is hissing for over 10 minutes until I shut down the boiler. After a while, I restarted the boiler power, and the pressure relief valve started to hiss in about 10 minutes.

The pressure reads just a tad under 5 PSI.
In case I got it wrong, here is a picture of the pressure relief valve, and picture of my controls. Water level looks good.

Appreciate any advice. Thanks!

adambnyc

It could be two thing. PRV gone bad. After they blow your supposed to replace them

Or

Vaporstat isn’t working and your boiler pressure is climbing too high and causing the PRV to blow.

What does the pressure gauge on the boiler say? Are you sure the gauge is working?

adambnyc

Wait, is that first picture the “PRV”? I “think” that is actually a main vent, need one of the pros to chime in.

If that’s the case, change it. I’ve had them go bad.

rhodebump

So that is the main vent? The pressure will mostly hover around 3 to 5 PSI, but it seems to want to stick to 5 right now.

adambnyc

I think so. It looks like it’s on a wet return and that’s where you usually find the main vent. PRVs are directly on the boiler itself. The pressure is also too high. Consider dropping the main to 1.5 on the vaporstat. High pressure kills vents on rads and main vents.

If your in a real bind to get the heat on, you can remove the main vent and cap it temporarily. But it should be replaced ASAP.

But please wait for someone to confirm that it’s a main vent. It’s looks real old and I’m not 100% sure.

EBEBRATT-Ed

That looks like a boiler return trap. It probably has an air vent on top that is making the hissing. Put your hand up their (carefully) it's one of 3 things.

Steam leaking out if air vent is bad
Sucking air in on boiler shutdown-normal
or air venting out-normal

Also you are running your pressure a little too high. I would set the main at 2 psi. Then you will have to adjust the differential to have the burner start when the pressure drops to 4 ounces. Do you have a low pressure gage on their?

a Vapor system which is what you have works best at low pressure.

I wouldn't fool with it until the weather warms up to normal

rhodebump

It's hot steam coming out of the vent.
I lowered the pressure to 2 psi.

I will upload a picture of my pressure gauge.

rhodebump

Here's a picture of the pressure gauge.
I also plugged the vent.
The system is cycling every 2 minutes. Do you think my differentials are set correctly?

EBEBRATT-Ed

you need to replace the vent and keep the steam pressure below 1.5 to 2 psi. Plugging the vent will make the system airbound

You shouldn't be getting steam into your returns. You need to find out where it is coming from. Do you have cross over traps?? post a few pictures of your radiation and piping

rhodebump

Yes, I will be ordering a new vent tonight, and I understand how the air in the system will prevent the system from being effective.

This is a two-pipe system. I think there may be a few radiators that do not have capsules in the steam traps. I will be tracking those down.

I have the main set for 2 PSI currently. I am trying to figure out what a good value for the diff would be.

EBEBRATT-Ed

As close to 0 as you can get