1 or 2 pipe???!!

dobro23

went to check out a potential boiler replacement job today and noticed some strange things. in my neck of the woods, residential steam heating is mostly one pipe but this house seems to have been originally a 2 pipe system. here are some of the weird things i noticed and im asking the forum for help on how i should approach this when i replace the boiler next thursday. in a nutshell, the existing boiler is leaking and was shut down last week. the homeowner has been planning on replacing if for a few years but now they have to. it is a huge smith-pac oil fired boiler firing around 3.00 GPH for only 6 (smaller) cast iron radiator. it was zoned at one time but the zone valves havent worked in years and we are planning to abandon one zone completely as they have a series of hot water fin tube and heat pumps for that section of the house. the 6 radiators that will be piped leave the boiler in 3" iron and then the pipes disappear into walls etc. no access basically. on each of these radiators is a 1/2" or 3/4" steam trap that says SARGO on the cover. BUT all these radiators ALSO have an angled radiator steam vent on them! the condensate pipe heads back to the boiler and when it drops to the floor there is a bullheaded tee with some new piping un the top run suggesting that there was a main line vent at one time that was RECENTLY removed and plugged. there is no F&T Trap that I could find not to say that is may exist in one of the crawlspaces under the house. when the condensate pipes ( from both zones even though we're only going to be using one) become wet returns they turn to copper and each have 1-1/4" brass check valves and then join each other in a tee which then goes up to the hartford loop connection. I done have enough exposed piping to check pitch per se but i can assume the original system was 2 pipe and supply is pitched away from the boiler. my first question is: do i remove the steam vents at the radiators, rebuild the traps, leave the main vent plugged, remove the check valves and pipe a traditional hartford loop? the new boiler will be a burnham megasteam (513?) i dont THINK the water line or water volume will be a problem. I will attach the few pics that i have as they may help you guys see something that i haven't. unfortunately there is no way to get pics of the things which i think are strange.

Jamie Hall

That was... once upon a time... a nice Sarco two pipe system. Replacement guts for the traps are available -- contact @Sailah .

There shouldn't be vents on the radiators, but before you take them off it would be worth checking to make sure that the high level dry returns ("condensate pipe") are intact -- and replacing the main vent on them, which you note was taken off. Without that vent, a two pipe system simply won't work.

An F&T shouldn't be needed anywhere (but see below).

What happens at the end(s) of the steam mains? Are there crossover traps to the dry return(s)? If not, you also will need vents there, sized to the mains. If there are, make sure they are working.

Check the pitch of the mains. If they pitch back to the boiler, that may work OK. If they pitch away, they should drip to a wet return (if there are not wet returns, then you might need an F&T there to allow the condensate as well as the air to get into the dry returns).

I'm not keen on check valves on wet returns -- shouldn't be needed, if the pressure is kept correct. Copper wet returns are fine.

Steamhead

When you fix this system, they'll want to reactivate the other zone. You can't beat cast-iron and steam!

Ironman

Make sure you order that MegaSteam with the M/M pse801 LWCO, not the CycleGuard 450. The CycleGuard will turn the burner off every 10 minutes.

New England SteamWorks

The MST513 sounds a little big for just 6 (smallish) radiators. I assume you measured the radiators? Maybe an MST396.

Was a lot of the house converted over to hot water? Is that why we have such a massive boiler connected to only 6 radiators?

Hate to see steam get torn out, but I hate to see a customer having to operate two boilers as well...

dobro23

yes. a lot of the house has been converted to hot water. 3 zones off the burnham v8 in the pictures. the entire second zone of steam no longer has radiators attached. the heat in that part of the house is mostly fin tube and a ductless heatpump in 1 room where there is no fin tube. the steam radiators were measured the max output of the 396 was right there ( maybe short by a little)

KC_Jones

dobro23 said:

yes. a lot of the house has been converted to hot water. 3 zones off the burnham v8 in the pictures. the entire second zone of steam no longer has radiators attached. the heat in that part of the house is mostly fin tube and a ductless heatpump in 1 room where there is no fin tube. the steam radiators were measured and pipe loss was approximated. much of the pipe isn't visible. the max output of the 396 was right there ( maybe short by a little) but our company erred on the side of caution and bought the next biggest size due the the design and uncertainties of the house and the unpredictable new england winters.

You do realize the limit is the radiation and putting a bigger boiler in won't put out any more heat. If you added up the radiation and it matched the 396 and you went bigger you are oversizing plain and simple. If the radiation is 396 which equates to 95k BTU output and you put in a 1 million BTU boiler you would put 95k BTU into the building. The boiler size has zero to do with the system output. Oversizing is just costing your customer money for no good reason.

And the way you worded that it sounds like you added pipe losses into the 396, which is also incorrect. You add up the radiation and match that to the boiler rating. The rating has a 33% pickup factor already in it.

dobro23

i will let our salesman know. perhaps i understood wrong or perhaps he did!

dobro23

thanks for the insight Jamie. not sure that i can get to the end of the mains. hopefully i can and will find either crossovers or main vents. i will search for a skuttle hole etc this week. in my picture where you can see the top of the bock water heater you can also see the return set up where all the returns from that zone tie together and drop to the floor and back to the hartford loop. in the top side is where there are some 45s and a nipple that have been plugged. i assume there was a vent here at one point. the fittings seem "new" do i use a regular gorton 2 or hoffman 75 main vent here or do i need something special? or maybe i just leave it plugged.

SWEI

Ironman said:

Make sure you order that MegaSteam with the M/M pse801 LWCO

Is that an orderable option now? (fingers crossed)

hvacfreak2

SWEI said:

Ironman said:

Make sure you order that MegaSteam with the M/M pse801 LWCO

Is that an orderable option now? (fingers crossed)

Mine came with the MM - PS801 last year.

dobro23

REVISITED!!
went to the jobsite again today. this time with the service manager and a rep from the supply house who is knowledgeable with steam systems. after poking around in crawlspaces and ceilings etc we DID find a few more things which raise more questions of course. first, we found 2 more radiators hanging horizontally from the ceiling in the garage. they are piped 1 pipe style off of the 2 pipe "zone" . they each have their own vent on them but no condensate pipe. they both ( and 1 other radiator) all feed off a 3" main that must tee into the other 3" main coming off the boiler. there is no main line vent on this branch. there are however 3 tees with risers that disappear into the ceiling. we were able to locate the end of these in a storage attic area and found that they are all plugged off. we are thinking that the furthest ones should be unplugged and have main line vents installed. these are also the furthest radiators from the boiler. approximately another 20 feet past where the 2 pipe system ends. another find was an F&T trap at the end of the main. were planning on getting a rebuild kit for this and all the radiator traps. also planning to remove the steam vents that are in the 2 pipe radiators and replacing the vents in the 1 pipe radiators. and possibly adding a main line vent at the condensate return drop in the boiler room after if comes back from the F&T? I don't think it's possible to get in it the steam main before the F&T but does it need one at all? how do i vent the air in the mains without one? attaching a few new pictures. nothing great. sorry.

Jamie Hall

Nothing like an older house, eh?