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ksg 01-29-2008 04:59 PM

single-pipe steam heat - psi seems too high!
I'm living on the 3rd floor of a triple decker with single-pipe steam heat (6 radiators). I had one vent that was *pouring* out steam - so I've replaced that vent and the system seems to be quieting down and the unit is warm. In my reading I came across a bunch of info about PSI that the system should run at and I'm concerned that my system is running too high. Before I changed anything on my system (including replacing the valve) I looked at all the settings on my boiler and here's what I saw:

It appears my boiler has 2 pressuretrolls (the first goes straight into the boiler and the second is connected to the low water cut off - why are there two?) that each have cut-in and differential settings and then there's a gauge showing PSI - here are the readings:

Pressuretroll 1: 9 PSI, differential 1
Pressuretroll 2: 5 PSI, differential 1
PSI Gauge: 20 PSI

I read that PSI in the system should be much lower (more like 2). Reccomendations I found online suggested setting the cut-in to .5 and differential to 2, so I made that change last night checked the PSI Gauge this morning and it was reading even *higher* (I think mid 20s).

So, here are my questions:
1. Why do I have 2 pressuretrolls? Do they do have different functions?
2. What should the settings on the pressuretrolls be?
3. How can I reduce the overall PSI in my system?
4. Is there something else I need to know??

Thanks in advance for your advice!

bigMikeB 01-29-2008 05:04 PM

1. You'd have to see what they are wired to in order to answer this.
2. I use the lowest setting possible in residential jobs, 1 psi is fine but hard to get most brands to set up that low.
3. Just with your setting of the pressuretrol.
4. Google Dan Holohan, he's the USA's best steam guru, he has published many great articles on just what your asking about. It was after the first seminar of his I started turning down the pressure on systems.

ksg 01-30-2008 02:02 PM

Thanks bigMikeB - I've been reading Dan Holohans stuff, but what I don't understand is why my boiler is even firing if the PSI reading on the gauge is so high.

If I set the pressuretroll to cut in at 1 and have a differential of 2, then the when the pressure in the system goes over 3 PSI, shouldn't the boiler stop firing until the pressure drops?

Also, I would have thought that when the system was cool (say if I had the heat off for a day) the pressure would drop down to basically zero, right? I even tried removing some of the vents (with the system off) to release any built up pressure, but the pressure doesn't seem to go down much.

bigMikeB 01-30-2008 04:31 PM

Have you thought that maybe the gauge is no good or the siphon tube is clogged? I use @ .5 lb cut in with a 1 differential. Also, check and make sure both of those pressuretrols aren't in parallel.

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