expansion tank trouble

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8nrider

New Member
Aug 15, 2008
118
new hampshire
Lite the boiler this evening, when i went back to feed i heard water dripping into the elbi xtv-110 expansion tank. went to check the expansion tank pressure and water came out of the valve. the tank is only 4 months old. It was the last piece to the system so once a recieved it . I plumbed it in and lite a fire. System has ran great until tonight. What would cause the bladder to fail??I am assuming a faulty bladder probably would not last 4 months in constant use. Was an elbi tank a bad choice?
 
What PSI is the system running at? and what pressure did you set the pre-charge in the Ex tank at? I assume this is the Tarm with 500 gallons storage in your sig?

coalatin' data as they say...

karl
 
Sorry I don't have an answer , but rather another question.

What should the PSI in the expansion tank be set at? I have 1200 gallons of hot water storage. Should the psi in the bladder tank be set to warm or cool sytem psi? I am thinking I should disconnect the expansion tank when my system is cool and reset it. The tank was installed with factory settings.

Thanks!
 
The tank pre-charge needs to be adjusted before you connect the tank to the system..The factory setting info is not always corrrect, it's always best to confirm the pressure. Adjust the pressure in the tank to what ever pressure you intend to pressurize the system to.

It looks like a large tank, was it sized to your system spec? The boiler has a 30lb relief valve?

hr
 
the system is at ZERO right now. Yes i believe it is sized correctly for the system. I run it at 20-22 psi high point to 15 psi low point. was working great. purchased the tank from cozy heat. they got me in touch with Elbi this morning , New tank is on the way!!!! great service hopefully will not happen again. the tank temp rating on the tank tag reads 210, spec sheet reads 240. I do reach the high end of 210 at times.Hopefully that was not the problem. But .....time will tell cuz i'm going to run the same temps in the new one.
 
8nrider said:
the system is at ZERO right now. Yes i believe it is sized correctly for the system. I run it at 20-22 psi high point to 15 psi low point. was working great. purchased the tank from cozy heat. they got me in touch with Elbi this morning , New tank is on the way!!!! great service hopefully will not happen again. the tank temp rating on the tank tag reads 210, spec sheet reads 240. I do reach the high end of 210 at times.Hopefully that was not the problem. But .....time will tell cuz i'm going to run the same temps in the new one.

210F is a tad on the high side, it may have caused the bladder failure. Just to be safe, you might want to set the temp down 5-10 degrees?

Pat
 
I would put a decent sized loop of copper (to reduce the amount of heat that gets dumped into the expansion tank) say a 20 ' loop of 1/2 or 3/4 copper? I would also plan your to set the system pressure of 15 LBS at a 100F temp, reducing the amount of volume you're putting in the expansion tank. but as HR says, first put the expansion tank to pressure, and check it first. I do a lot of solar work and ended up having to get a semi pricey digital tire gauge (they didn't have cheap ones back then) to set expansion tanks as even the good dial ones don't read accurately in the lower pressure ranges. I think I spent $40 or more for the gauge, but I use it every day. you can probably get a much cheaper one that's OK at least these days.

I don't know anything about the Elbi tanks. I've always used Caleffi's solar stuff or Flextrol.
 
Sorry to hear of an early failure. I was gonna ask if it was a hydronic tank or meant for a different application ( like a water heater expansion tank or potable water system), unfortunately I have seen it. Air pressure within the bladder is usually 12-20 psi ambient temp makes a difference. Do you have it piped in at point of no pressure change? Steam can cause early failure, 220 degrees will not. I haven't heard of that brand, its mostly Extrol around here. I have to admit I never check the precharge pressure, never had a reason to I guess. It has to be checked with zero system pressure and zero water touching the tank to be accurate, before install. You would have to have a severely undersized expansion tank to have an early failure, like 2 or more sizes to small. There are charts you can check to compare your system volume to the size you need for your application. Adding a loop of copper is not what you should do, dont forget PNPC.
 
yes i believe i have the tank piped in at the correct location. what do you mean by ambient temp making a difference, and what is PNPC? thanks
 
I was just suggesting the loop of copper as a heat dissapator as the system heats up and deposits hot water to the expansion tank. if you're replacing the tank, it's cheap insurance. the flow rate into the tank will not be much, but if it's a short pipe run, you could get some super hot water into the tank. this may be overkill, but in the solar world we can get slugs of 350 deg fluid.

PNPC: point of no Pressure change. as circulators create a pressure differential across a piping circuit, you will maintain the same pressure at the expansion tank/vessel. if you pump away from the PNPC your circulators will effectively increase the pressure in those circuits, reducing air problems by keeping it in solution.

Karl
 
i have a 30 psi relief valve right at the boiler feed, the expansion tank is right after a y strainer, just before the air eliminator, on the boiler feed just before suction side of the circulator.
 
seems that all is as it should be, although the expansion tank and feed valve are usually attached to the bottom of the air eliminator.
sounds like things were done right. I'd just double check the pressure in the new tank before you install it, and raise your system pressure to the same as the tank(15PSI?) once your storage pressure is not 50 F from the ground, but has been heated up to near it's low end operating temperature. if you have to handle expansion from 50F because that's where you set the pressure at 15 psi, you could over fill your tank. if you set it at 100 or 130 F you reduce the amount of expansion you have to accomodate with the tank.
I'm all about cheap insurance.

Karl
 
i have no feed valve , closed system, any need to add water a hose on a boiler drain before the eliminator works fine. Must be tough to hang an expansion tank the size needed for a system w/ storage but i imagine some have. thanks for all the replies i'm thinking it really was just a bad bladder.
 
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