Combined 1 and 2 pipe system

Todd_33

I'm trying to fine tune the heating on a 9 unit, 2 story building, circa 1920s. ) It has 7 apartments and 2 1000 sq ft commercial units. Original boiler, first coal, converted to oil, now gas. - I'm now experimenting with various placement of 6 groton #2s to see where I can improve the main venting. My old pressertrol pressures out at 1.5lbs, cuts in at .5lbs. Usually the boiler cycles once for about 45 minutes and then building is up to temp. No second cycle on pressure.



I'm trying to even out the heating but am confused about something. The commercial units are one pipe. The apartments each have 2-2pipe radiators in the living room, but in kitchen, bathroom and bedroom have one pipe. All rads are vented. To further complicate things, it looks like the 2 pipe on one side of the building drip (is that the right term - I mean where the condensate flows) directly into a vented ( a groton #2 ) wet return while on the other side they drip back into that side's steam main.



The various rads have a couple of different supply side valve types (regular and thermostatically controlled ( have parts missing .) I don't see any steam traps, don't know about orifices. And all the 2 pipe rads are vented with various vents ( groton #1, varivent, Dole#30 ).



I thought the 2 pipe rads aren't supposed to be vented but need some way to limit the amount of steam entering. I also thought those dripping back to the main need to have traps. I haven't cracked one open yet to see if there are orifices. I was thinking I would like to establish a base level of heating and that the vents are a wildcard that is complicating the fine tuning. I'm considering removing the vents and plugging the 2 pipe rads see what happens. - Does that seem reasonable? Any other thoughts on how to tackle this beast are much appreciated. I've been studying Dan's books and this site for about 2 years. - That is the extent of my expertise.



Thanks - Todd

Jamie Hall

circa 1920

is late to have what I refer to as the one and a half pipe system -- which was a system that looked like a two pipe system, but had vents on the radiators.  Before traps were invented.  You'll find it in LAOSH.



That said, where you have a radiator which is fed from the main and drips back into it, as you suggest you may have on one side of the building, you have what is, in effect, a one pipe system, only with two pipes feeding the radiators -- one at each end.  And condensate going back out whichever way is easiest.  And both sides piped the way they are the radiators will have to have vents -- no other way for the air to get out, when you think about it.  Not a conventional two pipe system at all.  The other side has to have radiator vents, too, if it drips into a wet return, as air can't be vented through a wet return.



I am deeply suspicious that this system may have been seriously knuckleheaded at some time (or, sadly, times) and may take some effort to straighten out.  So I am not a bit surprised that you are having some difficulty making it agree with what you read!



All that said, I think my inclination would be to treat the whole show as though it were a one pipe system.  You've already done step 1 -- your pressure is good.  Thank you!  The next thing is to make sure that your mains are fully vented.  You seem to be working on that.  All I can say there is -- the more the merrier.



The last step will be to balance the system, and that will involve working with the vents on the radiators.  On this system I wouldn't even try to use the radiator valves for control -- treat it like a one pipe, and keep the valves fully open at all times.  For control use variable vents or, if you want local thermostatic control, there are radiator vents which are thermostatically controlled.  You may want to try those.

 

Todd_33

Makes sense to me !

Jamie - I like what you suggest about treating the whole thing like a one pipe system. I'd read that using rad vents with 2 pipe was a no-no but now recall that was because it ruined the steam traps which I don't have.



Treating it like a 1 pipe will greatly simplify my approach. I presume that because there are actual one pipe rads in the kitchen, bath and bed rooms that the mains are pitched correctly to treat the 2 pipe rads like 1 pipe.



I'll do it! - Thanks for keeping my head from exploding.



Todd