Steam problem

Steve_35

We installed a steam boiler late last fall that's part of a Dunham vapor system. Most of the rads are taking care of by 2 3" mains. There are 2 or 3 (don't remember at the moment) rads off a 2" line that also supplies the return trap with steam. At least to the best of my admittedly limited understanding of exactly how this system works this return trap needs steam.

The problem is the rads on the 2" line don't heat up. My understanding is the most likely problem is a bad trap elsewhere but we also checked the traps on these rads and found one trap had the bellows removed. We installed a Tunstall capsule in that trap as well as a new capsule in the other rad(s) on the 2" line.

We found if we closed the gate valve on one of the 3" lines the rads on the 2" line heat up. If we open that valve and close the one on the other 3" line the rads stay cold. So we went through and changed all of the traps on the first 3" line. It looks like at least 3 or 4 of them were bad because the bottom of the bellows was very clean but we're still not getting heat out of the rads on the 2" line.

Are we looking a bad trap hidden somewhere here or am I missing something else?

Big Ed

Steam

Anyway the steam can travel up the return of the troubled line ?

Do yo have proper venting on that line ?

Steve_35

We were back there today

> Anyway the steam can travel up the return of the

> troubled line ?

>

> Do yo have proper venting on

> that line ?

Steve_35

We were back there today

replacing a broken trap.

We pulled the vent 2 of these rads share and verified it works.

We tried an experiment. There are 3 rads that don't heat. Two are on a common supply that starts at 2" off the header then tees with one 1 1/4" through leg going to the return trap and the other (branch leg) supplying the 2 rads. I should mention the returns from these 2 rads come together and don't run through the return trap. They share a vent in the basement.

We pulled the pipe that has the vent so now these rads should be venting straight to atmosphere. Fired the boiler and still nothing. Closed the same 3" main that seems to be the problem and the rads get some heat quickly. Open that 3" main and closed the other and no heat.

But the return is right there w/o any possibility of an air lock because it's open to atmosphere. So that seems to leave us with air moving from the return trap back toward the boiler causing a block at the supply tee mentioned above. At least that's the only thing I can see happening. My thinking is if the return is open to atmosphere and we're not moving steam then steam must not be moving down the supply.

Is there anyone around the Central NY or Southern Tier area that's very familiar with Dunham Vapor systems that'd be interested in doing some consulting? Dan, you coming to Cornell any time in the near future?

Mark Hunt

Can you


post a pic of where those two returns tie together and where they tie back into the return main?

I'm in Saratoga county, but let's see if we can diagnose this via the net first.

Mark H

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Steamhead

Something on that 3-inch main

may be pressurizing the dry return to the extent that the rads on the 2-inch main don't heat. Have you checked the crossover trap at the end of the main to see if it's leaking?

Do you get any air from the dry return when the system is running and the vent is unscrewed? If not, water may have backed up just far enough to block the vent. The Return Trap was there to prevent this, but you say these rads don't return thru the trap.

Also check the return trap- it may be leaking steam into the dry return. Tunstall can rebuild Return Traps if this turns out to be the problem.

And a couple more things- if there are "king valves" on the steam mains right as they leave the boiler, are these valves fully open? And is the boiler firing at the proper rate?

Mark, I doubt this would happen to you, but if you go there and do get stuck, call me and we'll arrange something.

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Mark Hunt

Steamhead


Will do!!

Mark H

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