Losing water & vents

colm

I have recent bought a c.1900 house with a one pipe heating system. This is my first experience of steam heat.
Two weeks ago I drained the boiler, refilled it to 2/3 in the water guage and started the system. Within three days the water was no longer visible in the guage. I stopped the system and the water level returned to just below 1/4 of the guage. I refilled boiler to 2/3 again and started the system. After about 30 minutes I found that several of the radiator vents were losing significent amounts of steam. At this point I switched the heat off again.

Having done a little research I did two things.
1) I replace almost all the vents (Gorton #4, #5) with new Varivalue vents with telfon tape covering the threads.
2) I reduced the cut-in on the pressuretrol (Honeywell PA404A) (from about 8 psi) to 0.5. The differential setting I left at 1.

Having started the system again, all seemed well initially. The heat come up albeit more slowly. However after a couple of hours three of the new vents were again releasing steam. The vents involved are those closest to the boiler and thus the once where I had the vent closed to a greater degree (maybe 1/5 open on the gound floor, 1/3 on the second floor).
This appeared to subside once the temp in the termostate had been reached (70 f).

Now as I understand it the vents are supposed to close once the steam reaches them. However this seems not to be happening. The text on the box containing the vent also leads me to believe that this should never happen.

If the mechanism to close the vent is that steam condenses and the weight of the resulting water closes the vent is this affected by how hot the vent itseld becomes ?

What else could be causing this. There do no seem to be any obvious leaks or traces from previous years that would suggest a problem.

Finally there are two vents on what I believe to be the return pipe (Dole No.1933). These are I assume to ease the flow of the return water ? Should I be looking to replace these vents also ?

Charlie_10

Steam leak

Check the pressure in the boiler. Steam pressure control may be clogged and there by not sensing pressure.

Losing water may be from a hiden leak either in the boiler or from a wet return below the boiler water line.

Ken_8

Or could also be

a blown air vent and/or radiator valve packing nut!

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tommyoil

Do you definately SEE the steam

Or could it be going into a vacuum after the steam shuts off.

colm

vents, stream, water, pressure - thanks and more Qs !

Charlie, Ken, Tommytoil, Thank you all for your replies !
Charlie: Yes, I wondered about this. The pressure gague seems to show the boiler behaving correctly.
It does not seem to go above the 1.5 psi mark. Then again if the pressuretrol and the gague measure from the same point it is possible that both are responding to the same incorrect infomation...? The returns are visible in the basement by the boiler and are not showing any signs of a leak (at least to my novice eye). I'm assuming that this should be fairly easy to spot as it would be water rather than steam at this point.
A leak in the boiler - I'm hoping that this is not the case. The boiler is fairly new (Crown Jamica, about 1996 I think). Certainly while the boiler is off there is no leak (water level does not drop in gague), but a leak in the top would only become appearant while the boiler was operating ... I'm looking for steam through the chimney in this case ?
But this if I were losing steam at the boiler would I expect to see the steam escaping the radiator valve ....
wouldn't it simply take the easy way out at the bolier leak reducing the steam in the radiators.... ?

Ken: All but two of the vents have been replaced with Varivalve vents so I find it hard to believe that three of them are "bad out of the box".
"radiator valve packing nut" ...( my wife believes the I am only 'nut' involved ) what and where is this ? Within the radiator ? Is it possible that there is a problem within the radiator that's causing the valves to misbehave ?

Tommytoil: Yes, sadly I can see the steam esacping the vents on the radiators using a dentist mirror and flashlight. This is what caused me to replace the exisitng vents in the first place. I could believe that maybe I had one new malfunctioning vent, but three from six, and on the radiators nearest the boiler. Too much of a coincidence ! That's why I'm starting to worry about something system wide.
"Or could it be going into a vacuum after the steam shuts off" ... meaning the vent is not allowing air in when the steam pressure declines, so when the boiler kicks in again the steam gets driven back up with no resistance and so drives to the radiator with dirt or with sufficent force to prevent the vent from closing ?
I am a little concerned about the boiler since I have to assume that the previous owners lived with this problem and simply refilled the boiler perhaps leading to problems here. I'm guesssing this as they had the pressuretrol cut in cranked upto near 8-9psi.
I'm considering investing in some new valves that could with stand a higher pressure level .... though I'm not convinced that this is not treating the symptoms rather than the problem.

I have to say while it's a little frustrating I'm stuck by the simple elegance of (at least the theory !) of this heating system.

Steamhead

Part of the problem

might be those Dole 1933 vents on the returns. These are actually made to be used on convectors- they're way too small for mains. No wonder they had the pressure cranked up.

Measure the length and diameter of your steam mains and we'll tell you what you need.



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colm

main vents

Thanks for the tip. I had not looked seriously at these.
The mains runfor about 14.5 ft in one direction, turning into a 1.5 ft 1 and 1/2 inch pipe sloping downwards and then turning back to the hartman loop. In the other dirction it runs 13 feet through a 2 and 1/2 inch pipe before swinging directly down in u-bend and back to the boiler.

Attached is a jpeg with the layout. Radidator number 2 is the most serious offender with losing steam. (Radiator #1 is large ... about 20 bars).

Any suggestions would be most welcome.

Steamhead

Are both the mains

2-1/2" pipe turning into 1-1/2" for the trip back to the boiler? And what about that baseboard? Is there a water seal on the return connection?

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