having pressuretrol issues - L404F

Spunky424

so i'm having issues with my honeywell subtractive pressuretrol (L404F). i have the main set to what i believe is 1.5PSI and the differential set to 1. i just installed a winters 0-5psi pressure gauge right next to the pressuretrol so that i can dial in the pressuretrol better compared to the 0-30psi gauge that the plumber installed. well doing some testing today the boiler cuts out at almost 2.5psi(via the reading on the new gauge). the pressure will bottom out at zero and the boiler will not turn on. after a while the boiler will turn back on.

is my pressuretrol bad? is my gauge inaccurate? i've included a picture of my pressuretrol settings.

as a side note. my boiler was being held out and i had to lower the main setting so that she would kick on. never had to do this before.

any help is much appreciated.

Jamie Hall

Your main is actually set at about 0.75 which is lower than a pressuretrol will go. Hopefully it didn't disconnect the linkage... try setting the main to half way between the first division and the division labelled "2" and the differential to halfway between the 1 and 0.5 marks and see what happens.

CantabHeat

It’s hard to get a pressuretrol to work right at low pressures. For that you probably need a vaporstat... same thing but much bigger diaphragm and thus much more sensitive.

neilc

or is the pigtail dirty / clogged ?

Spunky424

CantabHeat said:

It’s hard to get a pressuretrol to work right at low pressures. For that you probably need a vaporstat... same thing but much bigger diaphragm and thus much more sensitive.

ive been on the fence about a vaporstat, but i think i'll be biting the bullet. do you run one?

Spunky424

neilc said:

or is the pigtail dirty / clogged ?

any recommendations on how to clean the pigtail out? or should they just be replaced?

EdTheHeaterMan

Air pressure! The threads are 1/4", the same as air compressor hose fittings. If 60 PSI can't clean out the pigtail, then replace it. Put a union on it and a close nipple so it is easy to take it out next year for cleaning This way the wiring and gauge don't have to be removed.

Jamie Hall

On the pigtail... the low pressure gauge appears to be on the same pigtail, so if it's registering, the pigtail has to be open. Not that it wouldn't hurt to clean it out, but...

EdTheHeaterMan

Have a customer with a 2 year old boiler and it started to make more noise than usual. Had 2 pressure controls and a gauge on the same pigtail. Pressure was not too high and not too low on the gauge. Looked like Baby Bear's porridge "just right" but the pigtail was plugged solid. In just 2 years, now I clean the pigtail every year for this customer when the oil burner gets tuned up

Gauge and pressure controls are getting accurate readings all the time now.

neilc

yeah, set the Ptrol as Jaimie said above first before worrying bout the pigtail,
then worry about the pigtail,
I don't thing 60 psi is a good idea though,
gonna blow out the Ptrol and gage first and or also.

Spunky424

thanks everyone. i set it per jaimie's instructions and it cuts out at 2.5lbs and then will not cut in till after a few minutes after the gauge reads zero lbs. i have a vaporstat and a new pigtail on order. will get it installed and report back. can someone advise on what are some good initial settings to start for the vapor stat?

Jamie Hall

Try somewhere around 1 psi (16 ounce) cutout with a 0.5 psi (8 ounce) differential. You may be able to go lower on your cutout, but I prefer to see the differential at about half the cutout.

Spunky424

Jamie Hall said:

Try somewhere around 1 psi (16 ounce) cutout with a 0.5 psi (8 ounce) differential. You may be able to go lower on your cutout, but I prefer to see the differential at about half the cutout.

got it installed and it cut out at 1.25 PSI on my 0-5PSI gauge and cut in around 0.6 PSI. works perfectly. cant wait to start tweaking. noticed that the vents are alot quieter now and everything is warming up evenly again. thanks!

CantabHeat

> @Spunky424 said:
> (Quote)
> ive been on the fence about a vaporstat, but i think i'll be biting the bullet. do you run one?

I do. The original pressuretrol is still on there just set higher as a backup. I have the vaporstat set at about 0.8 PSI and that works well.

If the system is behaving it only builds a few ounces of pressure during the whole cycle. If the pressuretrol starts kicking in that’s usually a sign the boiler is surging and getting dirty and might need a skim or clean.

Some people seem to have luck getting a pressuretrol to work at low pressures by fine tuning with a guage and such but that’s really asking it to perform outside its intended range of sensitivity... but if it works then do it! In my experience it was just too inconsistent and sometimes would fail to trip back on when the pressure dropped again. The big diaphragm of the vaporstat is just a lot more sensitive and easier to fine tune.

Spunky424

CantabHeat said:

> @Spunky424 said:

> (Quote)

> ive been on the fence about a vaporstat, but i think i'll be biting the bullet. do you run one?



I do. The original pressuretrol is still on there just set higher as a backup. I have the vaporstat set at about 0.8 PSI and that works well.



If the system is behaving it only builds a few ounces of pressure during the whole cycle. If the pressuretrol starts kicking in that’s usually a sign the boiler is surging and getting dirty and might need a skim or clean.



Some people seem to have luck getting a pressuretrol to work at low pressures by fine tuning with a guage and such but that’s really asking it to perform outside its intended range of sensitivity... but if it works then do it! In my experience it was just too inconsistent and sometimes would fail to trip back on when the pressure dropped again. The big diaphragm of the vaporstat is just a lot more sensitive and easier to fine tune.

any chance you have a picture of the vaporstat and pressuretrol installed. i'd like to use the pressuretrol as a backup as well . thanks in advance.

KC_Jones

If you ever replace the boiler, size it correctly and get your venting right and you won’t have the need for any of this discussion. It will run at ounces all by itself.

Spunky424

KC_Jones said:

If you ever replace the boiler, size it correctly and get your venting right and you won’t have the need for any of this discussion. It will run at ounces all by itself.

unfortunately thats not an option and i'm working with what i have existing in my house. thanks for your input though.