Removing set screw from Honeywell PA404A to lower operating pressure

Jeremy24

I have a PA404A from Honeywell. It's an additive differential pressuretrol. The differential setting is accurate but the cut in is a bit inflated. With the differential at 1# and the cut in at the lowest possible value of .5# I see a cut out of 4.5#and a cut in of 3.5#.

I've ran the boiler with the set screw and spring completely removed and the boiler behaves better without them. The cut in is closer to .5# and the cut out is closer to 1.5#.

Honeywell rates the minimum cut in at .5#, are you expected to achieve this with the set screw and spring removed? I can't find any reference of this other than this mention by @ethicalpaul (2nd reply).

The system operates beautifully, where all the vents in the house close up before the boiler cuts out. And it properly cuts in after a drop of 1#.

I mostly wanted to make this post to provide a solution to other home owners with a PA404A that operates at too high pressure. I know you can change the cut in values with the calibration screw discussed in this thread, but it might be easier just to open the pressuretrol and remove the screw and spring. Does anyone foresee me running into problems?

Since fixing the pressure problems my system is much quieter and efficient. No more steam leaking from valve stems I haven't repacked and no more hammer from radiators who's valves wouldn't open due to high pressure which would build up water.

I do recommend you get a low pressure gauge to ensure your system is operating at the expected values.

neilc

@ethicalpaul has a youtube video where he does and shows this exact thing, I can't find that link right now, I think Paul is his youtube handle,

Paul, are you still funtioning springs less?

ethicalpaul

you’re going to get quite a bit of pushback from people on this, but yes I found that without the spring the damn thing is right at .5/1.5 exactly where we all want it.

The spring is definitely too strong for this device. The pressure required to click the micro switch alone is 1.5 psi

I’m using a Dwyer low-pressure switch with a timer relay to moderate my pressure now, so my pressuretrol is just a safety backup (with spring)

I made a too-long video long ago about this. Fast forward to about 20 minutes in where it gets to about 1.5psi. I knew hardly anything back then but here it is:

https://youtu.be/sp688Jdc2zM?si=fWY_hStJrKySv-OP

ethicalpaul

https://forum.heatinghelp.com/discussion/comment/1831903#Comment_1831903

sorry, we were writing our replies at the same time 😅 see above for answers 👆🏻

Chris_L

Yes, you can run these Pressuretrols without the spring. I've done it for years. However, you have to be sure the boiler reliably cuts back in after it cuts out. (I tested one old Pressuretrol where that was not the case.) Once you turn the cut-in all the way down, the spring isn't doing anything anyway, and the screw holding the spring may fall out.

As @ethicalpaul says the spring is too strong for low pressure operation. I found that even the spring in the microswitch alone was too strong. For a while, I had jury-rigged my own spring to counteract the force of the switch—by pushing down on the lever arm—and could get the boiler to shut off at about 1.25 psi. But then I found the thread about how to calibrate the Pressuretrol, and did away with that spring after doing the calibration.

Currently I am running without the spring, but the Pressuretrol just serves as a backup to a pressure sensor that turns the boiler off for 15 minutes if the pressure reaches about 1/3 psi.

EBEBRATT-Ed

I would be cautious about removing the spring.

I see what is going on and I understand these controls do not seem to be calibrated correctly right from the factory.

I also don't claim to be or want to be the "boiler police'

Altering a control to make it work is something to be cautious about.

We all have done it.

I can remember busting the lock tight off a MM #150 pump control adjustment screws to make it work the feed pumps the way I wanted. It also acted as a LWCO and the lwco still worked fine but I also had a separate additional manual reset LWCO.

So, for me if I removed the screw from the PA404, I would want an additional control to act as a high limit

Or install the screw and buy a vaporstat $$$$$

A homeowner can do what he/she wishes it becomes their responsibility.

As a former contractor I always wanted to stay out of the courtroom and out of jail so it would be two controls for me. Too much risk.

JMHO

CLamb

I have put a shim between the pressure sensor rod and the lever. I found that a piece of an aluminum soda can worked dandy.

EBEBRATT-Ed

I only mention what can happen. Murphy's law.

If you don't think it can happen to you it can. This was my only time in 46 years I ran into this and it scared me pretty good. I have posted what happened on this service call before but here it is again

Very late in my career before I retired, I was called out to look at a Burnham steel boiler 15 psi on a process job.

The call was for a burner issue flame rumbling

They always ran the steam at 9-12 psi for process.

When I got there the burner was firing and the steam pressure was 10psi. I got my combustion test kit and was setting it up behind the boiler which took a few minuets. When I came out to the front of the boiler the steam pressure was at 25psi on the gauge.

So I thought the gauge was bad. Shut the burner off just in case went to the truck for a gauge and put it on a spare tapping that had a valve. Opened the valve and the pressure gauges agreed.

Without going into all the details I had to wait until they were done running process and manually cycle the burner to keep the pressure normal.

The boiler had 1 operating pressure control and 1 man reset high limit control and a burner modulating control.

I took both limits off and both STEEL pigtails were plugged up and I could not unplug them

I put the pressure controls back on without pigtails (just for the night) They worked.

i also pulled the safety valve lever and it wouldn't open!

Finally got it opened and then closed and it leaked a bit under pressure. Checked the limit operation several times and let it run. Supply houses were closed by this time.

Came back in the morning with new brass pigtails and a new safety valve

So you can do whatever suits you but I would be leery of messing with limit controls.

It is possible for multiple things to fail at one time. Not likely, but not impossible.

mattmia2

There is also probably a much less expensive manual reset snap type pressure switch at around 4 or 5 psig that you could parallel in.