Basic steam questions.

bml207

So, I just bought my first house and it has a one pipe steam system. I hope you will forgive the basic questions. I have answered a lot of them for myself by reading 'We Got Steam Heat'.



A bit of background: the boiler (Dunkirk Plymouth II) was installed in June. I know that the main vent was also replaced with a Hoffman 75 (definitely working) and almost every radiator vent was replaced with Hoffman 40s. The main is 55 ft of 2 inch pipe. The system seems to work okay (as far as I can tell): the radiators all get hot at about the same time with no water hammer or other noise. The cut-in is set to 0.5 psi and the differential is set to 1 psi. I know the system needs to be skimmed (the installer is coming back next week to do that).



I suppose the first question is about the main vent: is it large enough? My second question concerns the radiator vents. Because the Hoffmans click when they open and close, I've noticed that they frequently cycle open and closed (at the extreme 5 sec closed, 1 sec open) during the heating cycle. I think this occurs after the radiators are filled with steam. Is this normal system behavior or a result of not being skimmed yet?



I really appreciate the help.

nicholas bonham-carter

big enough vent?

i would guess the single hoffman 75 you have is not big enough; however you state that all the radiators get hot at about the same time, so you could watch the system when the temperatures are coldest. make sure there is no short cycling during venting, as this is a waste of fuel. 

one thing that main vents do which is often forgotten: relieving the vacuum at the end of the cycle, so pay attention to the radiator vents at shutdown, and if they are whistling, it's not dixie, but the air trying to get back in.--nbc

bml207

Thanks

I have noticed that some of the radiator vents hiss somewhat when the thermostat is satisfied and the boiler turns off. I was considering adding a Gorton #2 to the system and it sounds like that would solve that problem.



As far as short cycling during venting, I don't think that's an issue, though I don't really know what to look out for. When the boiler is coming up to temperature and the main is filling with steam, the burner is on the whole time. I timed the Hoffman 75 and it is open for 5.5 min after steam starts leaving the boiler.



Thanks again.

Steamhead

The Gorton #2

will reduce your venting time quite a bit. With just the one main, all the boiler's output goes toward that one vent rather than several. So use the big Gorton!

Big-Al_2

Another

If you don't want to spring for a Gorton, you might want to tee in a second Hoffman 75.  I've been able to find them brand new on eBay for less than 50 bucks.

bml207

Thanks everyone

Looks like I'm buying another main vent. Thanks for all the help.



Any thoughts about my second question about the radiator vents rapidly cycling open and closed?