Should I install pressuretrol or vapostat?

Christopher Harrison

Hi,

Have a single pipe steam heating system that heats the house thoroughly at ounces of pressure (installed really sensitive gauge). Need to replace current old pressuretrol for unrelated reasons - Dan's book says that I'm better off with a vapostat, my contractor says that a pressuretrol will work just as well (pages 124-125 of "We got Steam Heat" for pictures!). WHAT SHOULD I DO?

Christopher Harrison

[Deleted User]

use the vaporstat..

ive been taught that there isn't a residential system in america that REQUIRES a pound system over ounces..customers of mine that ive installed vaporstats in place of pressuretrols report to me that their systems are quieter..why spend the extra gas/oil raising the pressure any higher than is necessary?

John Ruhnke1

Pressuretrol / Vaporstat

Chris,

A Vaporstat can be set to work in a Vacuum or under pressure. Steam under a vacuum is Vapor hence the name Vaporstat. Vaporstats have a reputation for being more accurate with the smaller numbers. Installers use them on nonvacuum systems because of their reputation for accuracy. Your system is not designed to run under a vacuum. Its a one pipe steam system. Your boiler was running between 2.5 and 3.5 pounds yet it was set for .5 pounds. My objective was to set your pressuretrol down to 1/2 to 1.5 pound range just like it reads on the switch. The switch wasn't able to accomplish this.

I called Prisco from Shelton Winnelson and asked him for a Vaporstat. He didn't have any. He then recommended a pressuretrol that has a mercury switch. He said it was more accurate then the pressuretrol already installed on your system. He thought it would work fine with a 1/2 pound setting.

I can do what ever you want. If other people think that the vaporstat is more accurate, I will return the pressuretrol and order it for you.

JR

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Steamhead

Chris

the L404 Pressuretrol that John got you is a much better unit than the little PA404 you have now. It is more accurate at the lower end of the scale.

If the system builds pressure quickly and short-cycles, the boiler may be too big.

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Christopher Harrison

Followup on vapostat vs pressuretrol

Hi Guys -

Great to see you guys here as well - what a surprise! John, let's discuss this further on phone - I need to figure out when Fred will be here next week as well. Fred, GREAT HOT SHOWER water this weekend, thanks!!!!! If you guys have confidence that the new pressuretrol will be sufficient, then we can go with that. I'm just surprised b/c we had initially discussed a vapostat. All I care about of course is to get something that works well.....but of course my Dan Holohan book recommends a vapostat as well. You can see my confusion!!!!!

Christopher

Tom_22

How Accurate Are Mercury Switch Pressuretrols In General?

> ...boiler was running between 2.5 and 3.5 pounds yet (the pressuretrol) was set for .5 pounds. ...objective was to set it down to 1/2 to 1.5 pound range just like it reads on the switch. The switch wasn't able to accomplish this.
==========

This brings up an interesting question. How accurate is the average mercury switch pressuretrol, especially when setting it for .5 to 1.5 ? Most of them have a range on the dial of 0 to 10 psi and putting the indicator at exactly .5 seems a little optimistic, but I'd guess most could get it within an ounce or two on the dial by eye.

But then, how close to what you set it at is it actually going to deliver? And aside from the original allowable tolerance when it was new, how many pressuretrols out there are just not working well and may be way off?

If getting a gauge to verify the setting, what kind do you like to provide sufficient accuracy?

Unknown

Nothing beats a water manometer for accuracy.

Buy a female hose end and about 8' of clear hose to fit it. Put it on the boiler drain, hang the open end up above the boiler alongside the gauge glass. Open the drain valve and the water levels in the glass and the hose will be equal (assuming no pressure or vacuum is in the boiler). When you make steam pressure, the water in the hose will rise. 14" is a half PSI.

You can FEEL the accuracy.

Take it off when you finish.

Noel

[Deleted User]

noels method works great,

a couple years ago you taught me that via this site, and what i did was build a test rig that i can hook to a faucet and inject water and watch it climb the clear tube, on another tap port i have the pressuretrol mounted..i set the 1/2 lb. cut in and 1 lb. differential then reinstall on the boiler..it speeds it up, instead of waiting for boiler pressure to build...ive found many pressuretrols scales to be off by alot..the scale may say its cutting in at 2 lbs. but its really cutting in at 1/2 lb..

James W.Stamo

pressuretrol

After reading this thread the past few days I wonder is Honeywell doing the right thing for the home owner? I can't
believe that millions of homes have such low tech measuring intruments ion their boilers.What a waste of natural
resources, I can't believe this, that nobody in this age of the computer has a better control than this primitive contraption the "Pressuretroll".It is beyond comprehension all these homeowners are getting screwed by Honeywell, there has to be a better way to adjust the pressure on a boiler.