Boiler serviced recently but still need 20 PSI to get water to radiators

teurizoa

I have a boiler maintenance contract through my gas provider, and they recently replaced several components:

• Expansion tank
• Pressure reducing valve (PRV)
• Pressure relief valve
• They also added an automatic air release device (I don't remember the exact name)

They did this because my boiler (gas, hot water) was showing 35 PSI when running hot, and it did not trigger the safety release.

Now, when I run my boiler, the pressure reaches 27–28 PSI.

I drained the boiler and tried to refill it, but I noticed that if I keep the PRV at 15 PSI, the radiators on the second floor do not fill up. I have to lift the manual handle on the PRV, which allows water to flow through and increases the pressure to about 20–22 PSI, and then the radiators fill up.

I have bled all the radiators.

I just wanted to hear some opinions from you all: what could be the issue? I'm going to try using a 0–30 PSI gauge to test the pressure through the drain pipe in case the boiler dial is wrong, but is there something I'm possibly missing?

I have seven radiators in total—four on the second floor and three on the first floor. The ones on the first floor have half-inch pipes and are quite large cast iron units.

mattmia2

If the prv is set right you should get water out of the bleeders on the second floor at 12psig unless you have super high ceilings or something. If you drain water out of the boiler does the pressure come back up possibly a bit slowly? Try the second gauge because if the gauge case gets twisted on it can throw the accuracy way off.

teurizoa

It's a little hard for me to read what the prv is set at because it looks like this.
What i did do is drain boiler, turn the screw counter clockwise to reduce pressure, let the water run, it fills till about 15psi (according to gauge on boiler) then i don't hear as much water making noise through it. I gave it 30minutes or so just to see if the radiators will fill up, but no dice.

However, that fills up the radiators on first floor, but not 2nd. Ceilings are standard.
I have to pull that lever up , get it to 20 psi, bleed radiator (goes back up to 15) and do it one more time for it to fill up.

However, it then stays at 20 psi.

EdTheHeaterMan

@teurizoa Based on your explanation, your gauge is not reading the proper pressure or you may be reading the wrong scale. If the gauge was correct, you should be able to get the water to rise over 30 feet above the gauge location in the basement. If your gauge is reading 15 PSI and the highest level the water reaches is 12 feet, then the actual water pressure is only a little over 5 PSI.

Here is are 2 slides from my Hydronics class that I used to explain Static Pressure.

The gauge at the boiler in the basement is measuring the weight of all the water above it.. If a gauge was placed at the top of the first floor radiators, then that would measure the weight of only the water above that point in the system, 7.7 PSI for example. That gauge on the first floor radiator would not measure the weight of the water below it.

Since the water is not going above the first floor radiators, then you have between 5 to 8 PSI at the basement and only 1 or 2 PSI above the first floor radiator. So your gauge is incorrect or you are reading the Feet scale, not the PSI scale.

Are you reading the pressure gauge properly. Some gauges have 2 scales on the pressure line. Feet and PSI. If you are reading the Feet numbers, then 28 feet of water is actually 12 PSI.

Test

teurizoa

Thanks Ed. I'm pretty sure I'm reading the gauge on the boiler as it's the only one there. Has PSI and temp below it. I will post a photo later.

For now I bought an adapter for drain so i can connect a 1/4 0-30 psi gauge to test it. The only part I'm not sure if i should open the drain completely or half way ? Or it doesn't matter much ?

mattmia2

Doesn't matter how much you open the drain as long as it is open.

teurizoa

PSI at boiler reads 20 and it has been off 24hours.
I connected a 3/4 to 1/4 adapter to the drain pipe, then connected the gauge to this adapter.
Opened the drain and the psi on the gauge connected to the drain read 12psi. It stayed there for 10seconds or so and i closed the drain.

Is it safe to assume that my boiler display gauge is wrong and is showing 8 psi more than actual psi ?
I had a few drops of water leak through the adapter since i didn't use teflon tape, not sure if it matters much.

Jamie Hall

https://forum.heatinghelp.com/discussion/comment/1810577#Comment_1810577

Pretty good assumption there… 8 pounds off for those gauges isn't that unusual…

teurizoa

Thank you!

leonz

Please buy an American Made Marsh Instruments triple gauge not a chinese one!

mattmia2

The gauge measures small changes in the curvature of a thin metal tube called a bourdon tube. If someone smacks into or levers against the gauge while they are working on the boiler they will bend it and throw the calibration off. This is how that type of gauge becomes inaccurate.

EdTheHeaterMan

Maybe the installer was consuming Bourbon when that pipe wrench slipped and hit the Bourdon tube on that gauge