Adding a low pressure gauge

cubicacres

We saw a 0-3 psi gauge we thought we'd try adding to our 0-30 psi gauge required by the city on our steam boiler to see how the pressure's going. Would a 0-5 or 0-10 psi gauge be better in case psi were to jump over 3 on occassion? We're not expeting that since we have our pressuretroll set for as low as it goes around 1-1.5 psi (I think) and things have been fine, but wondering how much over 3 psi a 0-3 gauge might handle before causing it trouble.

Jamie Hall

Depends on the gauge. Usually, however, you can find the maximum rated pressure somewhere in the fine print.

JUGHNE

Some will add the 0-3 PSI gauge next to the 30 PSI on a tee, but install a ball valve under the low pressure one, leave it off until you want to read it. This protects it from high pressure which you may notice on the 30# one if there is a problem.

A second pressure control as a high limit is not a bad idea also.

cubicacres

Thanks-we have 2 pressuretrolls on one pigtail, I think. We could add a pigtail with the 0-3 or 0-5psi gauge addition. Any thoughts on pipe configuration with them (2 pressuretrolls, one 0-30 psi & one 0-3 gauge)?

The manufacturer of the gauge said there's not much tolerence over 3 psi (2-3% above 3psi) or 5 psi for each of the respective gauges, so with pressuretrolls set at .5 cut in with a differential of 1 or 1.5, is a 2 psi ceiling enough of a safety margin to go with the 0-3 psi gauge, or would 0-5 or 0-10psi be a safer choice (but with less detail on the psi scale as a tradeoff)?

ChrisJ

I aim for 50% of the gauge.

Meaning, if you run 1.5 PSI, a 3 PSI gauge is good. If you run 2 to 2.5 PSI, go with a 5 PSI gauge.

cubicacres

We'd like to try as low as possible, so maybe a 0-3 is best for us.

ChrisJ

> @cubicacres said:
> We'd like to try as low as possible, so maybe a 0-3 is best for us.

As low as possible?

Steamhead

Go with the 0-3, and definitely add a second pigtail for the second pressuretrol. On a boiler like your W-M EGH, you'd come out from the side of the boiler with a 1/2" or 3/4" nipple and put your pigtails on a cross or a pair of tees. Unfortunately I don't have any pics of where we've done this on that type of boiler.

I like to install my gauges on 1/4" tees under the pressuretrols, with suitable extension nipples as needed. This way you can check to see that the pigtails are not plugged without disconnecting and removing the pressuretrols- by removing the gauges and blowing into the pigtails.

cubicacres

Thanks, we can buy the materials and do some research on putting it together then.

Gordo

@cubicacres : Sometimes a particular pressuretrol set at 0.5 psi *on* to 1.5 psi *off* may not actually cycle at those ranges and your new 3 psi gauge might be damaged unless you are careful.

We had one just recently that was supplied with new boiler that did not trip off until almost 6 psi!
https://www.youtube.com/watch?v=mE1-QuUx4_c

cubicacres

Thanks. We have an old brass pigtail from our prior boiler-are those ok to re-use, or should be get a new one? The PSI gauge company also has carbon steel siphons (pigtails, I think), but is brass the better way to go?

BobC

Clean out the brass and use that, brass corrodes a lot less than steel.

Bob

cubicacres

Sounds good if a 15 year old cleaned-out one can work just as well as a new one since we have some laying around. Do you reccomend cleaning with a flexible pipe cleaner/cloth or another method to just swab it out?

Does it just keep the hot steam out of the gauge to help protect it with some water condensing in the loop similar to how a plumbing trap works to keep the sewer gas out of a sink? Are they offcially called "siphons" & "pigtails" are the informal name?

BobC

Try boiling it in white vinegar, you might want to do it under a exhaust hood.

Bob

ChrisJ

All it does is keeps steam from reaching the gauges via the water trapped in the loop. I have my very sensitive gauges protected by nothing more than air trapped in a vertical pipe, works much better at low pressure and can't clog. I've never tested it over an ounce or two though, so I don't know if it would be reliable at higher pressures.

I also have a proper brass pigtail with the required 30 PSI gauge and pressuretrol on it.