Pressure setting vent sizing

daveamir

Hi guys I have been reading a lot of discussions on this forum and have thoroughly enjoyed everyone's wisdom and insight. I just have some questions if you guys could help me. I've attached pictures of my pressure controls what would be appropriate settings I have a 2 inch 45 ft main and a small second main 2 inch about 10 feet long, if I do need to change the settings I have how would I? I tried to see if will adjust by pulling but the lever doesn't move. My second question what type of main vent do you guys recommend I'm thing of buying Barnes and Jones big mouth for the end of my 45ft main, my second small main thAt is 10 foot doesn't have any vent attached, should I put bigger vents on the rads attached to the small main since it does not have its own main vent thanks for your time and wisdom.

KC_Jones

I don't see any pictures?

Jamie Hall

Well, I don't see the pictures. However -- if it is a standard pressuretrol, the outer setting (cutin) should be as low as possible -- say 0,75 psi -- and you should check the inner white dial, which should be set at 1. If it's a vapourstat, try setting the cutout at 12 ounces and the differential at 6 ounces.

A Big Mouth will surely work on the longer main. Bit of overkill, but in most cases there's no such thing as over venting. You should figure out a way to install a main vent on the shorter main -- say a Gorton #1 or #2. Increasing the venting on the radiators is not a good substitute for proper main venting.

BobC

On the pressuretrol you will find an adjustment screw on top, set the front tab so it reads 0.5. Then remove the pressuretrol front cover and set the white wheel to one which as low as it will go. That will allow the boiler to cycle off at 1.5 PSI maximum.

As to the main vents you will need a much faster vent on the long main than you do on the short main. The ratio would want to be about 4:1 but sometimes other factors come into play so that is not set in stone.

Bob

daveamir

Sorry guys, here is the pics of the pressure setting controls, thanks for the replys.

KC_Jones

Screws on top adjust the settings. It is way too high. Set both down basically as low as you can.

It is probably turned up due to lack of venting. The control is a safety not an operating control. To truly keep pressure down boiler needs sized correctly and plenty of main venting.

daveamir

So when I lower the cut in and the differential how will this make the system run better, sorry if dumb question. I'm going to install Barnes and Jones big mouth on main vent toomorow thanks for the comments guys.

daveamir

This is what's on my main vent now, this is probably the problem.

KC_Jones

Yes, unless your main is under 10' long that isn't going to cut it.

daveamir

45 feet long, one big mouth should do it?

daveamir

Thanks everyone for their replies I appreciated the help guys!