Proper psi setting for old American Standard + Honeywell pressuretrol

SteamingPile

background: I bought a house with an oldie American Standard steam boiler...don't laugh. I was hoping to make it through a few seasons with it since provided oil stays insanely cheap. Thing seems to be built (and sized) like a tank.

I grabbed "we got steam heat" from amazon and read it cover to cover, and probably will need to read it a few more times. One thing that stuck in my mind from the book was the information about just how low of a pressure a good steam system should be able to operate at. 0.5-2 psi.

It's got a Honeywell Pressuretrol and it's set somewhere around the midpoint between 0.5 and 5psi. There is also a gauge (no units, assuming its psi) that regularly reads 6-7psi when the boiler is cranking away. Am I missing another controller somewhere? I searched and I keep seeing threads about a main setting and a differential setting.

Should I play around with the pressuretrol and reduce the cut-in?

BobC

Most steam systems run very well at 1.5 PSI or less, my single pipe system runs between 4 and 12 ounces.

i would adjust that pressuretrol down to 0.5 on the front and then take off the cover and adjust it down to 1. That should let the boiler run between 0.5 and 1.5 pounds and save you some fuel.

The 0-30 gauge is really not very useful at the low end, you would have to add a 0-3 PSI gauge to tell exactly what pressure it's running at.

Bob

Fred

That Americam Standard apparrently is a great old boiler, according to a couple of the PRO's on this site who have experience with them. The Scale on the Pressuretrol should be set to .5 PSI. (Cut-IN), if you take the cover off of the Pressuretrol, you will see a white dial. It should be set to "1" ("1" facing you if you stand in front of the unit). That gives you a Cut-Out pressure of 1.5PSI which should work fine for you. I would encourage you to take the Pressuretrol off and make sure the small hole in the bottom of it is open. Also take the pigtail (looped pipe that the Pressuretrol is mounted on) off and clean it out. They often get clogged and the Presstrol can't see the pressure to control it. Once you do that, if the pressure still climbs significanly above the set points, let us know and we can post a procedure to recalibrate the Pressuretrol. Also, make sure your vents are working, both main and radiator. Running at the pressures you currently are, the vents can be damaged or stuck closed. It also a very good idea to add a 0-3 PSI gauge on that same pigtail so you can actually see what is going on. The old gauge may not be working properly.

SteamingPile

great info guys. thanks, will take a closer look tonight when I get home.

So just to be clear... assuming the pressure gauge is correct it should not be anywhere close to 6-7 psi... but closer to 2 or 3 psi assuming the pressuretrol is working correctly.

Fred

It should not be over 2 PSI. preferably less than 1 PSI. The Pressuretrol should be more of a safety device to keep the pressure from getting out of control. Under normal circumstances, the boiler should shut down because the thermostat is satisfied, not because the Pressuretrol shut it down. On very very cold days, the boiler may run long enough that an over-sized boiler may shut down on pressure but not a typical heating cycle.

SteamingPile

Hmm... that pressure gauge is directly screwed/tied into the boiler. There is no pigtail. Pressuretrol does have a pigtail.

An image search on google shows most setups with a pigtail, with a pressure gauge on one side of a t joint... pressuretrol on the other.

thanks for the continued input.

Abracadabra

SteamingPile said:

Hmm... that pressure gauge is directly screwed/tied into the boiler. There is no pigtail. Pressuretrol does have a pigtail.

An image search on google shows most setups with a pigtail, with a pressure gauge on one side of a t joint... pressuretrol on the other.

thanks for the continued input.

That gauge has an internal syphon, obviating the need for an external pigtail.

BobC

If you add a low pressure gauge needs to go on the output of a pigtail, most put a T on the pigtail and feed both the pressuretrol and the low pressure gauge.

Bob

SteamingPile

Man... you guys are fast... and good.

SteamingPile

So here is what I found after taking off the cover to the pressuretrol... Looks like it was set to 4?

Any idea why it wasn't set to 1 in the first place?

Fred

Some people think the higher the pressure, the faster the steam movement. Quite the opposite. In reality, however, the Pressuretrol is a safety device and, except on very very cold days or if the boiler is significantly over sized, the boiler should cut off because the thermostat is satisfied. Set it to "1".

SteamingPile

Thanks... I'll crank it down. I haven't figured out the sq ft for the radiators... but the boiler system seems on the upper end.. 713 sq ft.

Fred

That's a good size boiler. If your radiator EDR is much less, the boiler may short cycle a bit on longer runs but that's OK. Don't crank that Pressuretrol back up. The best operating effeciency is at the lower pressure.