Pressuretrol cutting out too high at lowest setting - options?

KarlW

I have a newish boiler (2010) on my 102-year old house. Since I purchased the house in 2012 I have replaced many of the original steam valves with thermostatic valves and then installed smart valves (Netatmo) on them. After a couple winters, I've calculated that zoning my system is saving me 8% on my heating bill.

This has led to another problem - too much pressure. When all my valves are open, my boiler operates at less than 1 PSI (the scale on my gauge makes it hard to read with more than 0.5psi accuracy). However when valves are closed, the system operates at much higher pressure and causes floor-shattering banging and even condensate leaks - this is where the pressurtrol comes in...

It's clear that the problems are due to too much pressure in the system. I currently have a Honeywell Resideo PA404A1033 pressuretrol. Even at its's minimum setting, my boiler doesn't shut off until 4psi.

Does anyone have any suggestions on a replacement pressuretrol that I can set the shutoff to a sustainable level?

Thanks in advance

KC_Jones

First, the banging isn't from pressure it's a condensate/water issue. Water is either getting where it shouldn't, or not being allowed to get back to where it needs to, when it needs to.

Is this a one pipe system or two pipe system? What type of thermostatic valves did you put on?

KarlW

Sorry, I lost my original post and forgot in my rewrite to point out that it is a 2-pipe steam system.

The thermostatic valves are all Honeywell, mostly V2040ESL of appropriate size (3/4" or 1").

What clinched it as a pressure-related problem was this morning when troubleshooting it with a technician I had all valves open going full-bore - no pressure reading and no banging. As soon as I closed off some of the valves the pressure in the system jumped up and the banging began.

At the very least the banging is related to the zoning, but pressure builds up as well. There's nary a sound when the system operates fully open.

Jamie Hall

ANY type of valving which sometimes shuts off part of a steam system is going to cause banging and overpressure and all kinds of mischief unless it is very carefully thought out and all the equipment is made for steam.

Any valve which closes a main or runout (or dry return in a two pipe system) must -- no exceptions -- have a condensate drip to a wet return installed on both sides of it. There are no options to that. Further, it must be a full port straight through valve -- reduced port or globe style valves are not permitted.

A valve which closes a two pipe radiator is a good deal less problematic, provided it is installed at the radiator inlet (otherwise, see the paragraph above). A valve on the inlet to a one pipe radiator must be intended for steam, and allow condensate to drain freely. Even then, it will tend to bang (or spit water from the vent) when it opens.

The Netatmo valves are intended for hot water heat, not steam, and are inappropriate if not flat out wrong for a steam application.

As @KC_Jones said, your banging isn't a pressure problem, it's a condensate problem and your zoning, while it may save energy, makes it inevitable.

Now you may also have a pressure problem on top of that. Make sure that the pigtail from the boiler to the pressuretrol is completely free and clear all the way into the boiler. Even so, it is possible that the pressure will overshoot the mark if a number of the radiators are shutoff at one time, as under those circumstances the boiler will be wildly oversized and, while it can stop quickly, it can't stop instantaneously.

KarlW

I appreciate the response.

All my thermostatic valves are on the inlet pipes with properly installed trap valves on the returns. I have operated the system with the simple dial control as well.

With that said I realize I may not stop the banging for the reasons stated above. My hope is that the banging at 1psi is far more tolerable than the banging at 4psi, and so I'm looking for a pressuretrol that can shut my boiler off at 1psi instead of 4psi.

To your pigtail comment. The pigtail is new in the last year and I am getting reasonable results on my pressure guage. The pressure also builds during normal operation as not all radiators are open during normal operation with the pressuretrol cutting the boiler off at 4psi - the same pressure value every time.

I am unclear why the valve controller itself, whether a smart one like Netatmo/EVE, a Honeywell HR90 (the only smart-ish valve controller I can find on the North American market), or a traditional dial would make a difference here. My understanding is that the control is less precise on a steam system, but it still exists. I can say from 4 years experience that the valves do work as designed - rooms I want cold at night get cold and rooms I want to keep warm at night get warm (I'll brace for impact in the responses).

EdTheHeaterMan

https://www.supplyhouse.com/Honeywell-L408J1017-Vaporstat-Controllers-0-psi-to-4-psi Is more accurate than the pressure control you have

Let us know if that solves the problem. There are those of us that already know the answer.

pedmec

Adding trv's to 2 pipe steam systems has the potential to cause serious banging issue due to vacuum forming in the radiators when the trv is satisfied. With the trv is satisfied with steam in the radiator will condense and create a vacuum. once the thermostat trap opens everything rushes toward the trap and the vacuum throwing condensate around. situation can become worse if there is a failed trap in the system.

Jamie Hall

Ah. This is two pipe. There is, in fact, no good reason -- other than having a wildly oversized boiler -- why thermostatic valves on the inlets to the individual radiators can't work. They can, and I dare say in your system they may work well -- at temperature control.

You have two quite separate problems. One is the banging. As I am sure you aware, this results from water being trapped where it can't drain. One of the first places I would start to look for poor drainage is at all the radiator runouts. Particularly when the radiator is off, water will collect in those, then, when the valve opens (particularly if it opens quickly) any water will bang -- and it doesn't take much to make quite a racket. In your system, with potentially closed valves, all runouts should be sized and pitched as though you were dealing with one pipe steam, not two pipe. Also check the pitch on all the radiators -- they must have a definite pitch towards the outlet rather than being dead level. This will help ensure that water doesn't accumulate in them (which will also, incidentally, prolong the life of your traps).

Now the second problem is both the pressure control of the boiler and, somewhat related, the fact that much of the time it is very poorly matched to the system demand. Both of these items can cause water to back up into higher level pipes where it shouldn't be accumulating and cause water hammer. There is nothing you can do about the wildly oversized condition; it is what it is. Two things will help some. The first is to figure out why your pressuretrol is allowing the pressure to climb above its cutout setting (and verify that cutout -- what is the cutin actually set for? What is the differential?). Pressuretrols can be out of adjustment; you could verify that with a low pressure gauge. The other thing is, again, to check all the piping. Anything which is above the water line (other than, obviously a drop from high to low) needs to be well above the water line -- at least 28 inches for every psi your boiler reaches. Conversely, and more commonly, anything below the water line -- such as wet returns in distant reaches -- needs to be well below the water line. It is not uncommon for a boiler replacement to lower the water line, which makes trouble. This may require some adjustments to the piping.

mattmia2

Another possibility, which @Jamie Hall gets close to at the end of his last post is that there are water seals that aren't very deep and the higher pressure is enough pressure to push the water out of the seal and allow air and then steam to pass and collide with the water in the wet return. You might look for these seals where there are drips from the mains down in to wet returns and see where they are in relation to the water line of the boiler.

This could be fixed by replacing/supplementing the pressuretrol with a vaporstat. Also add a tee and a 0-5 psi gauge with the vaporstat so you can see what is going on.

109A_5

Hello @Karl,
Check out this thread.
https://forum.heatinghelp.com/discussion/189715/pressuretrol-cutting-out-too-late

KarlW

@109A_5 I'll try that - especially because I feel this problem is more recent than my valve zoning. Unfortunately I don’t have a wrench that small…