Expansion tank and boiler

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by TonyBagadonutz, Feb 24, 2007.

  1. TonyBagadonutz

    TonyBagadonutz Electrician

    Messages:
    126
    Location:
    NJ
    My Mother-in-law (MIL) calls to tell me she has no heat.
    I go over to her place, and while checking things out my wife calls and tells me that the MIL has a "worry-free" contract with the gas co. I say "Good, call them - I'm coming home".

    My wife meets the gas co. man today...he quickly finds a burst pipe on one of the baseboard heating units. He also says that the expansion tank needs to be replaced ~ both are NOT covered by the contract. I tell my wife.. "I'll fix the baseboard and we'll see what happens"

    So I remove a 5' hydronic baseboard unit and replace and re-pressurize the system.

    3 hours later, I head back to check that all is well.
    Nope.
    The baseboard are not getting hot. The boiler IS hot (180° +/- degrees), pressure seems good (15psi +/-).

    Now I am left with a few questions:
    1 - Is is the circ. pump that has decided to take an unapproved vaction?
    I do have 120V across C1 + C2, so it seems to me that the relay and t-stat is working fine. I didn't have an amprobe to check for the .70A the motor plate states. Having power on C1/C2 also leads me to belive the control transformer is working "ok".

    2 - Is it one - or both - of the 2 zone valves on the system?
    The boiler supplies heat for 2 units in the 3-family apt. building the MIL owns. I could see one valve going, but not both at the same time.

    3 - What role does the exp. tank play here? If it were broken, would that prevent the hot water from getting to the baseboards?

    I am heavily leaning towards the circ. pump being bad here.

    Any help folks?
  2. TonyBagadonutz

    TonyBagadonutz Electrician

    Messages:
    126
    Location:
    NJ
    BTW...I attached hose from the boiler to a sink(as a drain) and was able to have the cold water(from supply) push the hot water throughout the system(both zones).
  3. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,348
    Location:
    New England
    If the expansion tank is shot, the pressure can bounce radically as things warm and cool - you need a space for the water to expand to when it is heated.

    It could cause the boiler to shut off from excessive pressure, or to pop the T&P valve.

    Usually, you can tell if the circulator is running. While they are usually nearly silent, they do make some noise. Stick a screwdriver on it and put the otherend in your ear to see if you can hear anything. Also, the temperature differential from one side to the other when stopped verses running should be fairly obvious.

    Many of the zone valves have a manual open lever. If the water is hot on one side, and cold on the other and the valve is getting voltage to open, then try manually opening it.
  4. ChrisNJ

    ChrisNJ New Member

    Messages:
    24
    Location:
    NJ
    Sounds like circ pump. I had a very similar problem a few years ago. I never fixed it because it was a rental unit and I moved out before it was repaired. I suspected the circ pump as well. Is it covered by the gas co.? :D
  5. TonyBagadonutz

    TonyBagadonutz Electrician

    Messages:
    126
    Location:
    NJ
    I didn't notice any water about the unit, initially.
    But it is sitting between the other unit and the HWH...could have dried it all up?

    When I went a few hours ago, there was still no water about the unit


    I tried comparing the pump from one unit to the other...I couldn't feel any motion. They are in a rather awkward spot for listening - so that won't be happening .
    Both sides on the pump in question were hot, very hot...as was a few feet of pipe heading to the zone valves....the other side of the zone valves were cold.
    All the pumps and zone valves are Taco models..

    I tried that too.
    I only waited a few minutes while MIL grabbed some clothes to come stay at our house tonight...in that time, the pipes did not get hot. By coincidence, while standing there holding those pipes, the other unit called for heat - that pipe heated up while the unit in question still remained cold.
  6. TonyBagadonutz

    TonyBagadonutz Electrician

    Messages:
    126
    Location:
    NJ

    Yes, the pump is a covered part.
  7. coz

    coz New Member

    Messages:
    91
    Location:
    MA
    easy to diagnose if i was there...1. open zone valve manually 2. shut off valve at purge station 3. open boiler drain at purge station 4. open fast fill 5. purge zone. (reverse steps) 1-5 ... turn on t stat make sure zone valve opens. lever moves freely when on stiff when off .check circulator after boiler is up to temp and off you can tell. will take 5 mins to diagnose
  8. coz

    coz New Member

    Messages:
    91
    Location:
    MA
    if you manually open the zone valve it should start circulating if the others are working.. (you have air in the system)
  9. coz

    coz New Member

    Messages:
    91
    Location:
    MA
    are you sure you have zone valves? do they have 3 wires attached to them or are they flochecks with thumb screws on top?
  10. BrianL

    BrianL New Member

    Messages:
    30
    Location:
    Raleigh, NC
    Expansion tank in older home

    Thanks for all the help in the last few weeks.

    Hopefully one last question.

    1992 house, no expansion tank off the hot water heater. The house does have a pressure regulating valve, but no backflow that I can find (I think the PRV acts as one?). I am installing a new water heater, should I install an expansion tank even though the house has never had one, and never had any water come out of the check valve in the previous heater? I am using PEX, how do I support the tank with plastic plumbing (it will be on a wall in the garage)?

    Thanks,

    --Brian
  11. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    Yes, install a Exp. Tank. Use copper for the first 3' or so coming out of the hot and cold from the heater then transition to PEX. You can install the tank and ball valve on the copper. If the tank is installed horizontally support the tank with strapping to the joist above.

    Be sure the tank and ball valve are on the cold (street side) of the water heater.
  12. enriquehobart

    enriquehobart Plumber

    Messages:
    22
    Location:
    MD
    You may have bad valves. I do believe that you are supposed to either disconnect power or stop the call for heat at the t-stat BEFORE putting the valves on manual. Putting them into the manual while the power is still on can destroy them.

    My other thought is that the system will need to be bled off at every bleed valve location.

    We were out on a call and one of these taco valves could not turn because there had been solder in the line that prevented the valve from turning. That valve ball was scratched (damaged) so the valve got replaced.

    GOOD LUCK.
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