best brand of pressure relief hydronic boiler application

archibald tuttle

i constantly have problems with drips on these units. has anybody had better experience with any standard 30 psi brands or models. given that they can't isolate for service or replacement, cost , within reason, is not the key concern. 

Jamie Hall

Any of the major brands should be fine. I'd be more worried about the possibility that you are getting pressure spikes -- or even constant pressure -- near their ratings.

jesmed1

archibald tuttle said:

i constantly have problems with drips on these units. has anybody had better experience with any standard 30 psi brands or models. given that they can't isolate for service or replacement, cost , within reason, is not the key concern. 

We have two oil-fired hydronic Weil-McLain boilers and don't have any problems with drips using standard Watts relief valves. What water pressure are you running, and are you sure your expansion tank still has an air cushion in it?

Mad Dog_2

I've never seen a garbage relief valve..As Jamie said,  maybe it's just doubt its job ..other issues are causing this.  Mad Dog 🐕 

archibald tuttle

@jesmed1 "What water pressure are you running, and are you sure your expansion tank still has an air cushion in it?"

@Jamie Hall
@Mad Dog_2

thanks for hitting me back.

I am running low 20s for pressure. expansion tank has space and oversized for this system and charged a few pounds above the fill pressure. get the problem just as much in the off season with boiler cold. it isn't that i'm hitting right around the trip point. these are watts blow offs, in this case on munchkins. and the things just like to drip. i did put a generic on a system at 15 lbs. last year that is dripping literally the week after i put it in. all of this is untreated pvd city water. higher chlorine or chlorine dioxide or whatever these days.

I have had pretty consistent problems like this with multiple brands. I'm probably exaggerating that it starts almost immediately after putting a new relief in every time, but just don't get the life out of these and not sure why. and lacking isolation can't readily ck. the seats or really get an idea why, nevermind that these aren't really made to be serviced. they still trip at the correct point but they aren't sitting against the spring all the time, this is just nuisance drips and it drives me crazy.

dko

Is it running low 20s for accurate reasons? Expansion tank pressure correctly set to match? If you've never put air in it until now, it's definitely wrong. Incorrect expansion tank pressure will render it useless regardless of it's size.

What boiler feed? After you have your system filled and set, shut it off and monitor if any loss of water over time.

jesmed1

archibald tuttle said:

I have had pretty consistent problems like this with multiple brands. I'm probably exaggerating that it starts almost immediately after putting a new relief in every time, but just don't get the life out of these and not sure why. and lacking isolation can't readily ck. the seats or really get an idea why, nevermind that these aren't really made to be serviced. they still trip at the correct point but they aren't sitting against the spring all the time, this is just nuisance drips and it drives me crazy.

I suspect it has to do with the seat design and the fact that they're relying on a spring with relatively low force to keep the valve closed, unlike a ball valve or gate valve where, when you close it manually, the sealing pressure on the seat area is quite high.

Yeah it's a nuisance, but as long as your bucket is bigger than your drip, you're good.

mattmia2

Maybe there is a lot of dirt in your system that ends up in the seat?

You say it happens when the circulator is off too. I could see a case where depending on where it, the circualtor, and the expansion tank are the circulator could increase the pressure at the relief valve enough to make it dribble sometimes especially if you're running a bit higher pressure. Why are you running higher pressure btw? Do you have enough height to need it?

hot_rod

If you have a high head circ pumping into the boiler take note of the dynamic pressure in the boiler. A 20 lb fill and a high head circ could be the cause.

Once they weep a bit they pressure relief valves tend to not seal tightly. A tiny amount of scale or dirt keeps them seeping.

A pressure gauge with a recording needle at the same location as the relief would tell the story.

I found the brass B&G to be one of the best valves. Bigger sealing surface.

archibald tuttle

@jesmed1 good point about the spring closing pressure being lower than you can effect with standard valving, and I guess that is the point. so maybe this a cycle i'm doomed to repeat.

love this: "Yeah it's a nuisance, but as long as your bucket is bigger than your drip, you're good." my floor drain can handle it, i'm probably just being too retentive. don't really think with the tiny make up additions i'm adding lots of air to the system so i guess i should have less palpatations.

@mattmia2 and @dko 4 story with fan coils. have trouble with circ and airbinding upper floor units if I don't keep the pressure nice and high. it's virtually maintenance free if I do (except of course this nuisance), but, as I pointed out, I have the same results with pressure relief weeping on systems running 12 to 15 pounds. this is just not a case of close to tripping, plenty of expansion, I am pumping away so highest effective pressures seen on system rather than boiler/relief side.

@hot_rod thanks for your recommend of hte B&G because of larger sealing surface and your experiential success. i'm going to go that way and see if i have a better longevity experience.

brian

Teemok

How you check tank charge is critical. It's nessessary for the system side of the tank to be at zero. Feed water off and open a boiler drain or relief valve (if you're that type) until gauge reads zero close it. Put 20 psi of air in the tank and open the system again till it's at zero again. I like to over fill "test" the diaphragm at 35psi. If no bubble sounds or loss after 5 mins. I release air to the correct charge pressure. Turn water back on. Note on tank with date and pressure. You might already know this procedure. I'm surprised at how many experienced plumbers I've met don't.

archibald tuttle

@Teemok sorry i missed this reply. i always provide isolation for the expansion tank. I should affect the be able to get that isolated pressure reading if I provide a relief on the tank side of the shut off.

WMno57

archibald tuttle said:

given that they can't isolate for service or replacement,

You can isolate the pressure on the system. Then when replacing the Relief Valve, the system is depressurized. You might even be able to put the system under vacuum by slightly opening the boiler drain valve.
Just isolate the pressure by closing the isolation valve for the expansion tank.
edit and close the fill valve too.

Teemok

The tank isolation valve can't be closed when setting the tank air charge UNLESS there is a open vent port/ bleed cap, purge port, hose bib or union in between the closed valve and the tank. Remember a low air charged tank likely has water in.
With system feed water/fill/prv shut off, opening the system relief valve will bring the system pressure to zero. If he tank air charge is zero but it has a good air bladder the tank still has water in it. As you add air to the tank badder it will push the water in the tank out into the system, raising system pressure. Opening the relief again brings the system pressure back to zero. This might be done a couple times until all the water is out of the the tank indicated when the air charge of the tank doesn't change when the system relief is opened and the system pressure stays at zero. Now you can test the badder with 50% higher than normal pressure. If it passes the test, let air out setting it to the normal system pressure ( I set 2 psi above) and open the system fill valve.

Daveinscranton

I looked at one that died at 3 years with a drip.  I don’t like to see anything drip.  Happened 2 months ago.  The system never sees anything over 15 psi.

There was a lot of rust at the seat.  It made me wonder if a bit of trapped oxygen (being at the top) hastened its demise.

I bought spares.  Seems that when I have a spare, the offending part doesn’t fail.  Murphy’s Law type of thing.

Given that it sat on top of a new mod con, the bracing was not robust.  I added some support to the piping so that the next time, I won’t have fear about the structural integrity of the tubing in the mod con letting go/bending.  Awkward place for me to get to.  Easier to get one wrench on it than 2.  Now I don’t need a back up wrench.

The Watts one I put on (only one I could find on a Sunday) looked to be a bit better quality than the Watts one that the unit came with.  The replacement was rated about 10% more btu capacity.  

hot_rod

Daveinscranton said:

I looked at one that died at 3 years with a drip.  I don’t like to see anything drip.  Happened 2 months ago.  The system never sees anything over 15 psi.

There was a lot of rust at the seat.  It made me wonder if a bit of trapped oxygen (being at the top) hastened its demise.

I bought spares.  Seems that when I have a spare, the offending part doesn’t fail.  Murphy’s Law type of thing.

Given that it sat on top of a new mod con, the bracing was not robust.  I added some support to the piping so that the next time, I won’t have fear about the structural integrity of the tubing in the mod con letting go/bending.  Awkward place for me to get to.  Easier to get one wrench on it than 2.  Now I don’t need a back up wrench.

The Watts one I put on (only one I could find on a Sunday) looked to be a bit better quality than the Watts one that the unit came with.  The replacement was rated about 10% more btu capacity.  

I mentioned the B&G up earlier. It is a brass body and has a larger diaphragm inside. So rust and corrosion is not an issue