old steel expansion tank leaking replacement help

Jamie Hall

You came back the next day and the pressure had risen again? More or less the same temperature in the system both times? If so, you have extra water getting in there from a higher pressure source. Could be a leaking shutoff on the automatic fill?

doctorman

Jamie Hall said:

You came back the next day and the pressure had risen again? More or less the same temperature in the system both times? If so, you have extra water getting in there from a higher pressure source. Could be a leaking shutoff on the automatic fill?

not sure how long is was leaking from high pressure we installed in back in Jan 20, noticed the high pressure few days ago not more than a week.
so I thought it was the autofill and that is why I shut the valve of the autofeed fully...lowered the pressure to under 20psi, next day it was back to 30 and leaking
today I went and lowered it to 14psi... will keep an eye
it can not be the autofill pressure greulator since the water to it is now closed
it could be a small expanssion tank, since the old one was 15 gallon bladderless but this new one is EX60 which is under 7 gallon, I chose it based on amtrol calculator for boiler os 200MBH
I might have to go up to EX90 or more.
it can also be a leak somewhere in the hydronic system closed loop connecting it to the house hot water?!

Jamie Hall

Let's make sure we have one fundamental really locked: check the system pressure, with the autofill closed off, at as close to the same system temperature as possible each time -- the temperature doesn't matter, but it needs to be the same or close each time.

If the pressure rises from observation to observation, then somewhere water from your domestic water supply is getting into the heating system. There is simply no other reason for the pressure to rise.

If the pressure rise from cold to hot is excessive, that's a different matter -- and it means that the expansion tank either was not precharged properly, or that it's failed, or that it's too small -- could be any one of those three.

It's unlikely that there is a cross connection between your domestic water and your heating, although it wouldn't hurt to trace some pipes and make sure. If there is, it must be removed. Not just valved off -- removed. The only permitted -- or safe -- connection is through the shutoff valve, pressure regulating valve, and a backflow preventer. No options on that one.

What kind of valve is used to shutoff the autofeed/pressure regulator? If it's anything but a ball valve, and a fairly new one at that, I'd be kind of surprised if it did shut off completely. However, it would also seem that your pressure regulator may have a problem, since it shouldn't allow any water to pass if the system pressure is higher than its setpoint.

On the expansion tank -- which, as I say, is another issue -- it may be too small. If the old compression tank was 15 gallons, that has a working volume of 7 gallons (oddly, the same as your new tank's overall size) and was, effectively, at least twice as big as the new expansion tank. What is the radiation and pipe size like in your system? If it's older, with nice big radiators and big pipes, chances are the new tank is undersized.

mattmia2

Does it have an indirect water heater or tankless coil?

mattmia2

I think I do see a tankless coil. If it does have a tankless and it is leaking, that will increase the system pressure.

Jamie Hall

mattmia2 said:

I think I do see a tankless coil. If it does have a tankless and it is leaking, that will increase the system pressure.

Argh. I wasn't aware of the tankless coil. Yep, a small leak in that would do it.

doctorman

mattmia2 said:

Does it have an indirect water heater or tankless coil?

I have no idea what that huge thing at the right side of the boiler room is, looks like hot water reserve tankless coil to my uneducated guess...
the autofeed valve is the yellow ball valve, it does not feel crudy or old, it closed smooth.
the boiler is set to run at 170F to 155F +-10F water temp, most of my measurments are around 170F +-10;
so if the pressure goes up from 14psi to over 30 in the same tempreture range I am dealing with a bigger issue. probably have to cut off the huge tankless waterheater from the boiler and install a new tank.

mattmia2

The tankless coil is I think on the right side of the boiler, to the right about half way down with an aquastat or possibly combination control mounted in it. It is attached to that black rectangular plate.

If you turn off the water to that, which I think is that gate valve with the stem sticking straight up near the ceiling and open an hot water faucet, does the pressure stop rising?

doctorman

mattmia2 said:

The tankless coil is I think on the right side of the boiler, to the right about half way down with an aquastat or possibly combination control mounted in it. It is attached to that black rectangular plate. If you turn off the water to that, which I think is that gate valve with the stem sticking straight up near the ceiling and open an hot water faucet, does the pressure stop rising?

So yeah the pressure was up again to 30 psi when the autofeed was closed. I lowered the whole system down to 10 psi and opened the autofeed. Came up to 12 and stopped. Closed the auto feed and heated up the system recording the temp against the pressure on the way up and down. Will monitor it tomorrow so I have more data point.

I believe I have a leak from high pressure home water to the hydronic system.
Also checked the baseboards.. they are fins not cast iron.. unless the tankless coil is messing up the expansion tank calculation I don't see how the ex60 is not enough.
 I think there is some air in the system as I hear the water move in the pipes. would that affect it somehow?

The tankless coil is my suspect.. what does it get replaced by? How would I size it? 

There is supply valve from hydronic system to it that I can close and there is the house water supply to it that I can close and see if the raise in the pressure still happens. Wondering if I have to empty the system few times since the coils will have 80psi home water in them for a while after I close the supply to the coil.

Jamie Hall

No -- just close the valves to the coil off. There isn't enough water left in it to affect the pressure.

ch4man

is that tank on the wall a shell and tube heat-exchanger that's being used as a potable water heater? if the tubes are leaking internally you'll overpressurize the boiler

doctorman

ch4man said:

is that tank on the wall a shell and tube heat-exchanger that's being used as a potable water heater? if the tubes are leaking internally you'll overpressurize the boiler

If it is leaking what do I replace it with?

mattmia2

I don't know what that huge pipe on the wall is or if it is even part of the heating system but the tankless coils is in the boiler.

ch4man

that tank is a heat exchanger. its a shell and tube design, what is used for unknown in your home but it appears to be piped to the boiler system. a leak in the tube and differing pressures will cause your woes. so, what's at the other end of all the pipes that are attached to it?

doctorman

ch4man said:

that tank is a heat exchanger. its a shell and tube design, what is used for unknown in your home but it appears to be piped to the boiler system. a leak in the tube and differing pressures will cause your woes. so, what's at the other end of all the pipes that are attached to it?

spoke with New Yorkers Boiler company, the boiler tankless coil is rear heater part number 6036031 https://store.thegranitegroup.com/Product/NY6036031
https://www.supplyhouse.com/Burnham-6036031-V1-2-Tankless-Heater-Assembly-w-Gasket-Bolts-V-1A-V-7-Series

which is 400-500$
there is no guarantee that the issue is not the tank/coil on the wall, they recomended just adding a new zone and an indirect water tank and closing off the tankless coil in the boiler all together... much better efficiency in summer that the boiler is off for heating.
I guess I have to find the best parts and pricing for that job now. The family want a tank that can handle 5 people showering back to back.
I will take any advice here. unfortunately, they don't have Gas at the house, while they have it in the street. I would love to convert to Gas but I believe it will be a very pricy job.
I know we dont discuss price but I think 1000$ for the coil alone or 2500 or so for the switch to indirect tank vs switch to gas close to 10k$ just my guess.

doctorman

ch4man said:

that tank is a heat exchanger. its a shell and tube design, what is used for unknown in your home but it appears to be piped to the boiler system. a leak in the tube and differing pressures will cause your woes. so, what's at the other end of all the pipes that are attached to it?

spoke with the New yorkers boiler company , the rear heater / tankless coil for the boiler is 500$ part 6036031 plus labor and we are still not sure if the leak is from that vs the external wall tank.
they recomended switching to indirect water tank by adding a new heating zone for it and and capping the tankless coil in the boiler.
probably 2500-3000$ in material and labor for adding the new zone and indirect tank.
I am considering this 45 gallon Mclain with an expanssion tank ST-12, circulating pump taco 007-f5..

https://www.supplyhouse.com/Weil-Mclain-633-600-001-Aqua-Plus-45-Pewter-Indirect-Water-Heater

would love to hear the pros advice on this

would love to switch to Gas as it is avilable in the street, but it is a costly switch and the indirect tank could still be used if later switched to gas.

mattmia2

So where are the outlets of both of those connected? Are both connected to the DHW system, both the heat exchanger and the tankless coil(or is the hx leftover from an older boiler that didn't have a coil?) Are the vlaves supplying both on? The first step is to isolate them one at a time (and that might be difficult if they ae both connected to the DHW without valves on the outlet) and see which one(if either) is leaking.

doctorman

mattmia2 said:

So where are the outlets of both of those connected? Are both connected to the DHW system, both the heat exchanger and the tankless coil(or is the hx leftover from an older boiler that didn't have a coil?) Are the vlaves supplying both on? The first step is to isolate them one at a time (and that might be difficult if they ae both connected to the DHW without valves on the outlet) and see which one(if either) is leaking.

tried to label the picture..
cold supply goes a branch to the wall coil and a branch to the boiler,
wall coil return hot to boiler's cold supply
I can close hydronic supply to wall coil but not return
I can close clod water supply to wall coil but the return of the wall coil is connected to the cold supply still without a separate valve,
so to test the wall coil, I would need to add a valve to the return from the coil and close it up. perhaps also a valve to the return of the hydronic from the coil.
the question is... how long will that wall coil supposed to live anyway? are they kind of life time thing so it is worth diagnosing and saving or just scrap the whole thing and go indirect with a new zone.
if the leak is really from the tankless coil I do not think its smart to spend 1000$ plus on it still unless the wall coil is real unquestionable part for a long time
another idea is to draw a 220V and put an electric unit, considering the price of oil/gas will be going up till at least 2025. the Hybrid Electric tanks are very efficient and cost almost the same as the whole indirect oil heating installation.
something like this 65gal hybrid Rheem tank with 600$ rebate https://www.homedepot.com/p/Rheem-Performance-Platinum-65-Gal-10-Year-Hybrid-High-Efficiency-Smart-Tank-Electric-Water-Heater-XE65T10H45U0/312741511