Need Expert Advice - High Pressure and Main Vent

warren_4

I have been reading Dan's books and working on my boiler for past 6 months. I am still trying to get it cleaned because I had all near boiler piping fixed to specs. I really need help with the fact that if the thermostat isnt satisfied and my boiler keeps running, my pressuretrol never trips. I have checked it and it set correctly at .5 and 1, and it will trip mannually if I push it up. I also added a low pressure guage which doesnt show it getting higher than 0.5. I have cleaned all the piping and it is clear. Is it piped correctly?



Also, I added some additional main venting and put #4 and #5 gortons on but it still sounds like most of the air is venting through the radiators. Could it be that my mains are on the return lines?



Thanks for everyone's help.

BobC

How long and clock it

How long are the horizontal runouts to the radiators? if they are 12-15 ft you might need some higher venting rates on those runs and the runouts should be insulated.



Do you know what the EDR of your radiators is and also what the boiler is rated at in sq ft of steam? Try clocking your gas meter to see if the boiler is using the amount of gas it should be. If the two are very close you may never build any real pressure.



If the radiator EDR is higher than the boilers rating you could have a problem, make sure all the piping in the basement insulated. Venting the returns instead of the mains should be fine. How long are the mains and what size pipe are they?



Bob

warren_4

Boiler is Sized Right

I had calculated the steam heat at 705 and my boiler is rated for 760 sq ft so seems to be sized correctly. I have 4 branches of mains and they run mostly around 20 feet with return about same so I have a lot to vent. I have maxed out venting on the small 1/8 tap that I have on the returns and may end up tapping the mains myself and adding 1/4 or 3/8 venting and close the return. I will insulate the rest of the pipe as you recommend including returns and luckily I was planning on doing this today since off work.



Any ideas on the lack of the system shutting down and pressuretrol. The system runs for about an hour to get all radiators hot and then it seems like it builds pressure because the radiators start squeaking a bit as it keeps trying to fill with steam but is already hot all way across. When I catch it and shut thermostat down, there is a rushing of air back in that lasts about 2 mins.

Jamie Hall

The way your boiler is sized

it is pretty close to what the system is demanding, so I'm not a bit surprised that it just keeps on going until the radiators are all hot (or the thermostat shuts it off, I presume?).  Just what it should do.  It's what happens once the radiators are all hot that's important.  If the system is perfectly balanced -- you should be so lucky -- it will just keep going.  The boiler making steam,, and the radiators condensing it just as fast as it is being made.  Perfect.  In most cases, though, we aren't quite so lucky and the pressure in the system will start to build.  At that point the vapourstat or pressuretrol should shut the boiler off all by itself -- you shouldn't have to "catch it".  The pressuretrol should be set at no more than 2 psi, and lower is better -- try for 1 to 1.5 psi cutout if you can do it.  They can be fussy at very low settings.  A vapourstat would give you better control



The squeaking you hear is most likely to be thermal expansion as those nice radiators heat up all the way.



The air rushing in when the burner turns off is perfectly normal -- it is surprising how fast all that steam will condense once things start to cool off.

warren_4

Seems like high pressure

The question I have is it normal that if the thermostat is not satisfied that the boiler will keep making steam even after radiator is hot and valve closes. It then starts spurting a bit as steam pushes the radiator valve open. I thought that the pressure would build and shut down the system when it is full. That is why I was wondering if my piping was correct on the guage and pressuretrol. Thanks for all the help and advice on the wall... I dont know what I would be doing without all the help here and Dans books.

BobC

Probably fine

As close as your boilers capacity is to the radiation I doubt you would build any real pressure in normal operation, if you were coming back from a deep setback you might see more pressure. As it is you are condensing the steam just about as fast as the boiler can make it.



Do you have 2ea Gorton #1's on each of your 20 ft mains? If that is 2-1/2" pipe you would have about 0.68 cu ft of air in each main and the #1 is rated at 0.33 CFM each so that should work fine but if your dealing with long radiator runouts you might need a bit faster venting on the rads with the long runouts.



The piping around the gauge and pressuretrol look fine. The boiler will make steam until the thermostat is satisfied.



Bob