2 pipe steam ...no traps

bluemoon

Anyone have any experience with a 2 pipe steam system with no traps, vacuum or any device at all...just 2 pipe steam...feed & return. There are no vents on the steam convectors...in fact they are totally inaccessible. Two steam mains along with the return lines (dry) circle the basement, picking up radiators along the way, until they reach the opposite side of the basement (opposite the boiler) where there are main vents, one each on the mains & returns,,,4 total. That's it! no other vents or traps...although @ the last connection of the last return drip leg to the return to the boiler there is a check valve???to keep condensate from backing out of the return...??...this is a 2 level home & most rads heat except for some on the 2nd floor........we have replaced the main vents with hoffman #75's...does anyone know the name of this system?

Ken_8

We've seen more than our share of

these.

Got any details? Photos? Question # 1, what's the pressuretrol set at?

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GW

I visited one

a few weeks ago, I believe you looking at an ancient system with either orificed inlets or special return valves. Proceed with caution. What do the valves and elbows look like? The job I saw seemed pretty normal looking- although my awarness has been increased after I visited the job the first time I started reading the lost art again.

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GW

what kinda house?

Is this an upscale home? Is the boiler original or was it swapped? If it was swapped, any signs of foul play ( that is, bozo work) ?

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bluemoon

thought the vents might not be dropping back out so after he changed the main vents my tech lowered the trol before he left for the day....jury's still out...cold tonight...i'll hear in the am

bluemoon

Yes...an upscale home...rumor has it that the system was designed by the original homeowner, a commercial engineer in NYC....the boiler was replaced 3 years ago...it is sized correctly....i have to believe the common thread must be in the convectors themselves...an orifice or bi-metal?...can't get to them though without wrecking the joint!

Unknown

The check valve is a clue.

If it's OLD, it means there might have been a return trap or alternating reciever on it, confirming that it's vapor, as Ken was hinting at.

If it's new, it shows that the pressure was too high, and a misguided effort was made to keep the water in the boiler. Of course, it just steamed away and wound up on the back side of the check valve, anyway.


What pressure is it set at?

Noel

bluemoon

It's old

The system is old....the check valve is original, not added...it's also at the **** end of the return, nowhere near the boiler itself, at the last drip connection to the return which is still wet @ this point

Unknown

hmmmm

If there is nothing between the check and the boiler, it might still be for a return trap.

I haven't seen one out there before. What are your thoughts?

Noel

bluemoon

vents

The check valve connects from a smaller circuit of radiators...I think it may be there to prevent the bigger circuit from pushing condensate up into the smaller...just a guess....we merely changed the vents as a starting point..the vents that were there did not appear original...reduced from 3/4 to 1/4 (3/8?)....we increased back to 3/4" & installed hoffman 75 main vents...i'm wondering if the previous "chemist" added vents where they didn't belong...maybe the system should only have vents @ the end of the return so that the radiators vent to the return...being that there are no vents on the radiators (as in a one pipe ) the system makes pressure in the mains as opposed to in the whole system??...I mean the radiators have pressure but don't have to be hot...they are acting like a one pipe system rad with a broken vent...ya' think?...anyway..can't get in the house today...kid has the flu...i have time to think

Dale

Wet return

Any chance the system with the old boiler had all the rads drop individualy to a wet return? No rad traps needed then.

bluemoon

dry

the return main is dry until appx 8' from the boiler

Steamhead

It's Orifice Vapor

and I'll bet it's a Trane. Check the convectors, I'll bet you find that name somewhere on them. The orifices on those Trane convectors were cast into the element itself. You can't remove them- but you don't need to!

First thing you need is a Vaporstat. This type of system runs on 8 ounces or so. Excess pressure will blow steam into the dry returns- which can cause banging.

Vent your steam mains as well as dry returns. I like Gorton #2 vents on these systems, they will vent lots of air at very low pressures. You could double up the Hoffmans on the dry returns and use the big Gortons on the steam mains if you wish. How long are those mains, and what pipe size?

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bluemoon

no access

One of the problems with this job is that the convectors are built into plaster walls...I would love to take one out to examine it but I would have to wreck the wall...We have no banging ....just some rads getting hot on the supply side just up to the rad....not across the rad itself..the mains (2) are appx 50-60' ...2".....the problem rads are @ the end of the main on the 2nd. floor. What exactly is the theory here anyway....if steam gets through enough of the closer rads & to the return vents...they close...the boiler reaches pressure (very low)...shuts down...how do we get the other rads hot?...i'm assuming the balance of this system is in the piping (orifice sizing?) since there are no vents...slow heating makes it work?...less is more?

Steamhead

Vent your mains

with a Gorton #2 on each one. Then change the Pressuretrol to a Vaporstat and set it to cut off at about 8 ounces (you may have to experiment with this). This should solve your problem by getting the steam to the ends of the mains faster, and keeping the steam out of the dry return.

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bluemoon

manual low pressure

OK...I've ordered a vaporstat as per your friendly advice...accessed the house yesterday & simulated low pressure by manually shutting down the trol when the system began to build pressure....system seemed to operate the same way...we have #75 hoffmans on the supply & return mains...not fast enough?..thanks

Unknown

While you're trying that,

pull the vent(s) off the return(s) and run it up to 8 ounces. If no steam comes out of the vent tappings, and it vents fast and heats fast, you have it made.

Fast vents will act a lot like that. There shouldn't be any pressure in the returns.

Noel