What to do with stuck PRVs on clean and checks

TechTok

Hello, I'm a service tech and the company I work for now wants us to drain steel expansion tanks on every clean and check. Im not keen on this for the reason that 1 90% of the tanks don't have airtrols and take forever to drain, 50% don't have isolation valves, and basically every PRV gets stuck open when you try to re feed water into the system.

If I had it my way I would have bypasses pipes around the PRV on every system as well as airtrols but as you know you have to work with what you got. 

So what would you do? It's not fair to the customer to make them replace the PRV that is never going to be used unless there is an issue and at that point it probably won't work anyways. 

JUGHNE

If stuck that means failing.....could fail stuck open or never open.

Is the water supply left turned on to the system and is there a low water cutoff?

If replaced and exercised/tested at maintenance visits would probably always function properly.

TechTok

JUGHNE said:

If stuck that means failing.....could fail stuck open or never open. Is the water supply left turned on to the system and is there a low water cutoff? If replaced and exercised/tested at maintenance visits would probably always function properly.

Yeah they are always left on and rarely is there a LWC on a hot water system.  You're right if tested yearly it would probably work. 
 So I probably need to replace them. 

EdTheHeaterMan

Are you talking about "Draining the Expansion Tank"... the type without a bladder?

Have you tried this?



First of all, I know there are some mistakes in this illustration because I use it to explain other problems... and this is found in many old basement systems from the 1950s thru the 1990s. So go off-topic and explain the problems and confuse the issue if you think you need to be heard.
Sarcasm intended.

On topic: To get air in this expansion tank you can place a garden hose on boiler drain valve B (this can be any valve with a hose thread in the system as long as it is below the expansion tank)

Now Close Valve C to make sure there is no additional water added to the system.
Next open Valve B to take the pressure off the system. (this will cause the water in the upper floor radiators to be at a pressure lower than atmospheric pressure. AKA a slight vacuum) now any opening in the system above the boiler drain will allow air to enter the system. Including leaking radiator valve packing nuts and the like, so do this next step without wasting time.

Start with an empty 5-gallon bucket

Open valve A and let air into the expansion tank. fill up a 5-gallon pail 2 times for a 15-gallon tank, 3 times for a 20-gallon tank ... you get the picture.

Once there's 10 gallons (or 15 or 20) of water in the bucket, there is an equal amount of air in the expansion tank.

Close valve B close valve A and open Valve C

You just "Drained the expansion tank".

You may also want to operate the relief valve during maintenance visits too. It's a moneymaker if you do it right. @DanHolohan has a story about that. I heard it at a seminar many years ago. I have told a similar story in every Hydronics class i have taught.

JUGHNE

Yes, that is another issue. I test the pressure relief valve as long as I have a replacement close at hand.
Often boiler inspectors will open one....probably not allow enough water to flow to flush the seat .....and then it is dripping.
If it will not stop he writes up for a replacement.
Who can argue with the man with the clipboard?

I was required to replace a steam pop off because part of the metal tag was missing.....it still tested OK and reseated but....the tag.

TechTok

EdTheHeaterMan said:

Are you talking about "Draining the Expansion Tank"... the type without a bladder? Have you tried this? First of all, I know there are some mistakes in this illustration because I use it to explain other problems... and this is found in many old basement systems from the 1950s thru the 1990s. So go off-topic and explain the problems and confuse the issue if you think you need to be heard. Sarcasm intended. On topic: To get air in this expansion tank you can place a garden hose on boiler drain valve B (this can be any valve with a hose thread in the system as long as it is below the expansion tank) Now Close Valve C to make sure there is no additional water added to the system. Next open Valve B to take the pressure off the system. (this will cause the water in the upper floor radiators to be at a pressure lower than atmospheric pressure. AKA a slight vacuum) now any opening in the system above the boiler drain will allow air to enter the system. Including leaking radiator valve packing nuts and the like, so do this next step without wasting time. Start with an empty 5-gallon bucket Open valve A and let air into the expansion tank. fill up a 5-gallon pail 2 times for a 15-gallon tank, 3 times for a 20-gallon tank ... you get the picture. Once there's 10 gallons (or 15 or 20) of water in the bucket, there is an equal amount of air in the expansion tank. Close valve B close valve A and open Valve C You just "Drained the expansion tank". You may also want to operate the relief valve during maintenance visits too. It's a moneymaker if you do it right. @DanHolohan has a story about that. I heard it at a seminar many years ago. I have told a similar story in every Hydronics class i have taught.

That's a very interesting way to do it. That may be something I try out.

As far as the pressure relief.. definitely check it on every one. Also make sure steam haven't had the wrong one installed (30 psi)

I pull the burners and clean them, check the thermocouple pilot assembly, drain the steel tank if there is one or check to make sure bladder is good in extrol style. Check the aquastat function, check the reducing valve...which is always failed. Check the pressure relief. On steam check the LWC and auto feed. Open the blow down and flush it out. If it's float style feed and LWC I pull the plugs and flush them out.