Correct pressuretrol setting

Shemp

Can someone advise if the settings on this pressuretrol are correct?
Thank you.

Big Ed_4

One and one is safe for those controls ,... Really we all use the P404 for price but there range is too high for residential. If you push it down too low they will sit closed .... The better control is an vaporstat that is set down to ounces .. There is an formula to set them as per the system ... I never had chance to set an Vaporstat ... I think I seen only one

Shemp

So are those settings wrong? I have no idea what I'm looking at.

Jamie Hall

Looking at the pressuretrol with the clear cover. That type is subtractive. You need to set the main at your desired cutout pressure -- say around 1.8 psi or 2 psi -- which is more or less where it is -- and then set the differential for a smaller number. If it were mine, I'd set the differential a little lower than what you have it set for, as where it is I'm not sure there is enough margin for it to reliably cut back in.

I presume the two are wired in series, in which case the grey one is serving as a safety backup.

Shemp

Ok, thanks!

Shemp

How do I set them? The screw on the top of the diff and the screw on the front of the main?

Fred

There should be two screws on the top. One towards the front, over the Differential scale and one further back, over the Main scale. The screw on the front just holds the plastic cover on.

Shemp

Thanks.

Gordo

In my considered opinion, the L404A series Honeywell pressure control is a total design fail! It is the worst pressure control model I have ever tested.

Both the Honeywell PA404A and the L404A have the same area size diaphragm underneath them that operates their respective cycling mechanisms, but the PA404A is better designed with the added bonus of not having poisonous mercury in the control.

I would recommend removing the L404 and properly deposing it.

https://www.youtube.com/watch?v=JgdHYQsa5hg

Shemp

So should I remove the top one and just use the bottom grey box one?

Gordo

Yes, I would remove the L404A. I would also lower the pressure setting on the PA404 (the grey box) to the lowest setting possible.

Questions for you, sir... how many BTUs do you have going into that boiler? Is it heating a multi-family dwelling?

If your boiler firing rate is greater than 400,000BTUh, or it is heating a multi-family dwelling, I would replace the L404A with a manual reset type pressure controller. Most codes demand it.

It is a good idea to install that manual reset control anyway, regardless.

I would replace your "pigtails" underneath the pressure controls with ones made of brass. It defeats the purpose of setting pressures low if the controls can't detect the pressure in the the boiler in the first place due to a rusted/clogged pigtail!

https://www.youtube.com/watch?v=mwLNeDeYW64