Vent mains longer to reduce pressure?

cnjamros

Hello again!

I have a system that is a bit over pressurized, due to the way it is radiated (explicit details at link below)

http://forum.heatinghelp.com/discussion/153593/one-hissing-howling-radiator-convector-everything-else-finally-balanced#latest

At the end of the main, there is a 3/4" tapping... on which I have 4 Gorton #2s and 1 Gorton #1 (the maximum, I believe, for a 3/4" tapping).

I also have 2 Gorton #2s at another location in the system, effectively about halfway up the main. (see attached diagram)

Currently my mains vent pretty quickly, which is great... once the radiators start to fill, however, my pressure goes up quickly, and radiators start to hiss/howl, etc.

I'm wondering if it would make sense to move those two additional #2s and ADD them to the 3/4" tapping at the end of the main. Even though the venting is effectively throttled by the tapping, perhaps having 2 additional large vents will allow the venting to continue for a little longer and keep the pressure down.

Basically, once the original 4 #2s have closed, the tapping can continue to feed the additional #2s for a while longer, perhaps reducing the pressure vs the radiators.

Does this have ANY merit at all???

Thanks again, everyone!
Chris.

Mark N

What is the Net EDR of th boiler? What is the EDR of your rads? How long does the boiler run on a call for heat? If the boiler is way over sized pressure will be high. Have tried running boiler at 2 CPH if you have a Honeywell thermostat.

cnjamros

Net EDR is 446 sq ft.

As far as I can figure, EDR of my radiators is 312 sq ft (see diagram above).

For EDR, I only use the sum of the radiator EDR... I don't include the pipes themselves, correct?

Mark N

Correct that is figured into the pick up factor which is 33% above the 446sqft. You are 43 % oversized.

ChrisJ

I like Mark N's idea about trying 2 cycles per hour if possible. It may help you greatly.

I don't see any easy solution and I don't think venting your mains any differently will change anything.

To me, it looks like this.

Your boiler has an output of 143,000 btus.
Your radiation can only condense 74,880 btus.
You have 68,120 btus extra and that is why the pressure is climbing.

Personally I feel piping should be included but it can be difficult to figure out. My mains and piping seem to dissipate around 2,000 btus but I'm pretty well insulated at this point.

Have you had a pro that come in that really knows steam? If it possible to downfire the boiler any?

Jamie Hall

As has been said -- you are oversized. In my humble opinion, you need to do one thing first: turn the pressurestat, if that's what you are running on, down to no more than 1.5 psi cutout -- which is as low as it will go. Yes, the boiler will now cycle once the mains are full and the convectors are filling, but it has to because it's just too big.

Then, if you are still getting banshees from the radiator vents, you can try bigger vents on the convectors. Or, if it is easy to do, you could add big vents on the runouts just before they get to the convectors.

cnjamros

Alas, the vaporstat is at 4oz/2oz.

And all of the convectors are quiet... It's only the one radiator/convector in the master bath that is howling (photo below).

Some of the bigger 5-tube rads hiss, but the bathroom radiator/convector is the most, shall we say, "wakeupatnightish".

Abracadabra

cnjamros said:

Alas, the vaporstat is at 4oz/2oz.



And all of the convectors are quiet... It's only the one radiator/convector in the master bath that is howling (photo below).



Some of the bigger 5-tube rads hiss, but the bathroom radiator/convector is the most, shall we say, "wakeupatnightish".

Did you try a different brand vent on the noisy convector as was suggested in your other thread?

cnjamros

Found a thread with a specific vent suggestion (ventrite #1) and am ordering one today. High hopes.