problems with pressuretrol not coming on

DomesticEngineer

We currently have a PA404A 1033W pressuretrol that has given us intermittent problems since we bought the house in 2008.  The steam boiler was installed in the 80's. The first two winters we were able to resolve the problem by removing the pressuretrol and pigtail coil and cleaning out the coil and reinstalling the pressuretrol.  We flush the float reservoir and check water levels weekly.



This year the pressuretrol still seems to "stick" in the off position, most noticeably after it hasn't been for a while.  Most of the time simply tapping the pressuretrol is enough to wake it up and it turns on.  We had the local heating company people come out and they recommending replacing the pressuretrol but also cleaned out the coil again.  I WD40'd the joints that  pivot the spring with the pressure valve and that seemed to help for about two weeks.



When running it doesn't go all the way down to the cut-in setpoint for the pressure, but does seem to cut out correctly for where it is turning back on.  I've seen other comments like this and it seems 'normal'. 

Should I also think about replacing the 0-30 psi gauge on the boiler with one that would be much more accurate at the levels I should be using? (0-3 psi)



What is the general life of a pressuretrol? Is it really time to replace it?  Vaporstats seem to have better reviews than these pressuretrols.  How do I choose a new vaporstat if that's what I need to do?

Jamie Hall

Pressuretrols...

do die.  Not, however, for a long time -- usually.  What is possible, however, is that the cut in pressure is set too low (!).  You don't say what you have it set for, but anything less than half a pound is going to be really problematic -- even for a brand new pressuretrol



You can't replace that 0-30 psi gauge.  Every code I've ever seen requires at least one pressure gauge on a boiler with a maximum range of twice the pressure relief valve, which is almost certainly 15 psi.  So leave it be.  What you can do is add -- either on the same pigtail with some T's and fittings or another one -- a 0 to 3 psi gauge.  A lot of folks have done that.



There are several models of vapourstats available; you'd want one which broke the circuit on a rise in pressure.    If you are running one pipe or normal two pipe steam, you'd want one with a 4 psi maximum setting.  If you are running vapour, you'd want the 16 ounce maximum setting.  The new vapourstats, with the microswitch, are pretty good and reliable.  The old ones, with the mercury switch, are just about bulletproof -- but you can't get them new any more.

Tim McElwain

is this system

24 volts, 120 or millivolts on the pressuretrol?

Dave in QCA

pressuretrol not accurate at low settings

I agree with everthing that Jamie has said.

My only comment is to relate my own experience.  I too tried to use my pressuretrol to regulate at very low pressures.  My boiler rarely cycles long enough to raise any pressure, but I still wanted to set the limit low.  I found several things.  One, the scale on the pressuretrol is very innacurate at low settings, probably the whole range is + or - .5 psi.  So, as I was trying to set it at 1 psi, it could be off a 1/2 lb either way.  In my case, at the low setting, if I had enough pressure to trip the pressuretrol, it would not trip back to the on position, even at 0 psi.  I had to raise the setting on the cutout in order for it to work reliably.

To deal with this, I have added a vaporstat and a low pressure gauge.  I found a 30 oz gauge and a "new - old stock" mercury vaporstat on ebay.  It is a 0-4 psi vaporstat.  I have it set to cutout at .5 psi with a differential of 4 oz.  I have found it to be accurate within 1 oz.

DomesticEngineer

pressuretrol mV and low pressure setting

Yesterday I raised the Cut-in pressure system (it's an additive system) to something more like 1.5 psi.  It didn't come on this afternoon again so I went and raised it a bit more to 2psi.  Again just tapping the regulator turned it on before I changed the setting.  As before it continues to cycle once it gets going.  My pressuretrol set at 2psi, runs up to a cutoff of 6 psi the 0-30 guage on the boiler and a cut-in at 5.  (at least it's following the 1psi differential, right?!)



I already had the differential set at the lowest that I can since I've often read that greater than two psi can cause problems.  So should I be worried that it's running at 5-6 psi? 



The current pressuretrol has cut-in (addititve) settings of 0.5-9psi.  I don't even understand why would they even make a 9psi additive differential setting!  I have trouble understanding how these are considered "very low" pressures when they are the recommending operating pressures.



As best as I can figure we just have this on a normal 120v AC house circuit.

Dave in QCA

2 psi max

For residential steam, it really should not exceed 2 PSI.  It sounds like it's time for a new pressuretrol!

DomesticEngineer

Make or Break Vaporstats....and water level height

How do I determine if I need a make or break vaporstat?  Or should I just find one that can handle both such as the Honeywell L608A?



Also wondering if part of the problem might be the location of the pressuretrol in relation to the water level.  We have to keep the waterlevel in our watch glass at less than half otherwise it looks like the base of the pressuretrol is at the same level as the water.  Should we look at putting an extension on when we replace to eliminate future problems?



Makes you wonder about how much the installers know sometimes....

Jamie Hall

In answer to...

the last question first, not much sometimes.  Discouraging.



Reading over your various posts, though, it is time -- it is past time -- for you to purchase and use a 0 to 4 psi, break on rise vapourstat.  Seriously past time.  First off, the behaviour of your pressuretrol indicates that the delicate linkages which go from the diaphragm to the switch are either gummed up (likely), excessively worn (also likely), or both -- which is very likely indeed.  Time to bid it a respectful farewell.



Then install your vapourstat.  Set it for a cutout pressure of 1.5 psi and a differential of 1.0, for starters (vapourstats are subtractive).  You are allowing your system to run at much too high a pressure for any residential (and indeed most commercial) heating system. 



And it isn't a low differential you should be shooting for -- it's a low cutout pressure.



The installation height should be such that the connection to the boiler is significantly above the normal water line.  Hopefully there is such a port available on your boiler.  Also, be sure to use a brass pigtail on the thing; I prefer having a snubber on vapourstats, but not everyone bothers with that (I run at such a low pressure that even minor bobbles can cause false trips, which is why I use one).

DomesticEngineer

make or break?

Vapourstats are saying they all all subtractive differentials and that's fine... but how do I determine if I need a Make or Break model?

Rod

Vaporstats

Hi- Attached is some info on Vaporstats.

- Rod

jpf321

vaporstat models....

L408J1017 for 0-4 psi

L408J1009 for 0-16osi



best price available to me... www.simplyplumbing.com ...but you have to call in the order. tell karen you know JP

BobC

use a voltmeter

In domestic boilers the pressuretrol is usually wired in series with the oil burner, once it opens (or breaks) the oil burner shuts off.



If you have a multimeter you can measure the voltage across the pressuretrol when the boiler is running, you should read 0 VAC. If the system shuts off because it reaches the pressure setpoint you should read 120 VAC. That indicates the pressuretrol opens (or breaks) on rising pressure.



Note that if the boiler shuts off because the thermostat is satisfied the pressuretrol will still be on (in make mode) because you have not reached the pressure setpoint.



The spare PA404-1033 that i have on the shelf (just in case) opens on rising pressure.



Bob

DomesticEngineer

Thanks everyone.

On my way to getting and installing a new vapourstat.  All I have to do is choose between the 1009 and 1017 model and order

mblmatt

same issue with pressuretrol

I am having the same issue as DomesticEngineer, bought house in 2008 and now having issues with the pressuretrol where i need to tap the side of it to move the mercury to the right side to turn on the boiler.



the reason for me chiming in here is to get a clarification on what is being recommended here. Do I replace the pressuretrol with a vaporstat or does it get added in addition to?

i am not quite sure what the difference is of vaporstat and pressuretrol.

thanks

BobC

Make sure it's level

A mercury bulb pressuretrol has to be level to work right. make sure the pigtail beneath the pressuretrol is oriented correctly, if it's not expansion on the pigtail (as it heats up) will throw it off. The pigtails loop should be parallel with the side of the pressuretrol.



Bob