Expansion Tank - Where to squeeze it?

dgoldstein

I have a 2400 sq. ft. living space across 2-floors heating via a Munchkin 80M w/Vision 1 ODR.

My PRV started leaking. I replaced it. It's still leaking.

Checked system pressure and it was 30-32 psi.

Checked expansion tank, thud - dead.

Went to replace with a EX-30 based on my boiler's Net BTU as per Extrol's calculator and realized my system has a EX-15 and there is no physical way to jam the EX-30 in there.

I feel fairly certain the EX-15 is undersize for my system.

I'm wondering whether or any of you think it would be mildly kosher to remove the EX-15 and re-route it's line up towards the alcove ceiling where I could mount an EX-30 off a Nexus Flexconsole via some PEX and maybe push-on connectors? I can solder pipe, but if push-on is satisfactory then I'll go for that since it'll go in faster.

I also realize that the lifespan of this boiler is nearer to the end since some critical parts aren't available anymore. I service this boiler and replaced the blower fan assembly myself several months ago after troubleshooting an intermittent failure of the original. This is a R1 80M from 2006. I also installed and programmed the Vision 1 ODR.

The boiler is controlled by a t-stat since I have a very leaky house and tried dialing in the curve to run 24-7, but due to improperly sized baseboard and drafts, living spaces would invariably become too hot or too cold. There was no temperature consistency through the house. Main turn on via the t-stat with the Vision 1 handling water temp control while running has been the best I can do. Utility costs are affordable so that's not a driving factor to get this system perfect.

So, surely this whole mess will get replaced within the next few years. But, I want to try to keep it going as long as it holds together before an irreplaceable part fails.

Thanks folks for any advice!

...and speaking of expansion tanks, my hot water heater doesn't have one. Should it?

Big Ed_4

I would just replace it with another 15 or recharge it to your normal system pressure ...

EBEBRATT-Ed

@dgoldstein

For your boiler expansion tank just unscrew the old one you have a valve there then 2 nipples and two threaded 45s and you can put the bigger tank in. I assume the bigger tank would hit the wall. You might want to add some support.

If your not having domestic water issues you don't need an expansion tank

Intplm.

Some have piped a tee just behind the relief valve to add an expansion tank (behind)! the relief valve.
You can do that, and valve off the defective #15 and abandon it. And install the#30.
That is if you can't reach the old #15 and replace it with the #30 in the same place? It looks like it is in a very bad spot that cant be reached?
Can you reach the old tank?

GroundUp

The Extrol calculator (among others which size via BTU) are merely guidelines based on averages and do not actually calculate necessary tank size. If this is a low temp system, the #15 is more than adequate for 2400sq ft of floor area. I am wondering though, why your system pressure is so high. 1 psi will lift 2.31 feet and you want to have a few pounds for buffer on the highest point, so if the highest point in your system is (for example) 10 feet above the expansion tank, you only need 4.33 psi to get it there. Add in 5 psi for a buffer and you're still well below the factory precharge of 12 psi in an Extrol #15.

dgoldstein

@Big Ed_4 - the replacement ex-15 is out for delivery today

@Youngplumber - thank you for that insight. I don't believe my system is closed.

@EBEBRATT-Ed and @Intplm. - unfortunately, there is no way for me to physically fit the 30 tank. I tried and there isn't enough clearance behind the boiler and the wall, not enough clearance where the 15 is due to the proximity of the gas piping, power conduit, boiler in/out pipes and wall. The only "free" space is up above everything near the ceil and/or hanging off the adjacent stairwell stringers.

@GroundUp - yes, my system curve is designed to run below 200*F. As of late it's been running around the 150*F temp with an outdoor temp of ~20*F and t-stat set to 68*F. The new replacement EX-15 is out for delivery today. I'll likely be installing that tonight and returning the EX-30.

I will let the EX-15 acclimatize, then check the pressure and adjust as needed to 12 psi before installing.

EdTheHeaterMan

Are you referring to the pressure reducing valve or the pressure relief valve when you use PRV.
If the automatic feed PRV is the part you just replaced, then you may just need to adjust it 12 PSI after you replace the #15. If the safety blow-off PRV is the part you just replaced, then it will most likely stop leaking after you get the #15 replaces and the pressure adjusted to 12 PSI cold start pressure. Hold off on replacing the parts that are doing the job they are designed to do until you actually fix the cause of the problem.

Respectfully submitted,
Mr.Ed

dgoldstein

@EdTheHeaterMan - the Pressure Relief Valve on the boiler was leaking, replaced it, still leaks, then determined the expansion tank was shot. Will be replacing the expansion tank tonight.

I haven't touched the water supply automatic feed valve. The system pressure has been around 12psi at the gauge on the boiler output since I re-inflated the old expansion tank's bladder despite it having a slow air leak while awaiting the replacement to show up. Despite this, the new pressure relief valve I had install still leaks a little bit, but I can't say for certain that the pressure didn't go up while I wasn't looking or over the course of the night when it gets colder and the system temps go up.

EdTheHeaterMan

There may be a little debris in the valve seat. Flush the valve really well with at least a quart to 1/2 gallon of boiler water under pressure... until the water runs clear. That may dislodge the debris. Sometimes a slight tap on the valve will help seal the seat.

Good luck with your repairs.

Yours Truly,
Mr.Ed

PS
Read the tag on or the instructions with the new relief valve and follow the instructions. Especially the part about operating the valve at least once a year to be sure that passageways are clear. Nobody ever tells you about that.

dgoldstein

I replaced the expansion tank last night and flushed the pressure relief valve a bit. I had set the tank to 12psi after it had acclimatized to where it was going to be installed.

As of this morning the system pressure on the boiler output was reading about 14psi. I noticed a small quarter sized amount of water in my boiler's PRV drip pan - though I hadn't fully dried it the night before so I'll be checking it again after work today.

Thanks all for the help!