(206) 949-5683, Top Rated Plumber, Seattle
Results 1 to 12 of 12

Thread: Expansion tank and boiler

  1. #1

    Default Expansion tank and boiler

    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. #2

    Default

    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. #3
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    Location
    New England
    Posts
    21,428

    Default

    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.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  4. #4
    DIY Junior Member ChrisNJ's Avatar
    Join Date
    Feb 2007
    Location
    NJ
    Posts
    24

    Default

    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.?

  5. #5

    Default

    Quote Originally Posted by jadnashua
    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.
    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


    Quote Originally Posted by jadnashua
    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.
    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..

    Quote Originally Posted by jadnashua
    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.
    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. #6

    Default

    Quote Originally Posted by ChrisNJ
    Sounds like circ pump. ... Is it covered by the gas co.?

    Yes, the pump is a covered part.

  7. #7
    DIY Member coz's Avatar
    Join Date
    Feb 2007
    Location
    MA
    Posts
    92

    Default

    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. #8
    DIY Member coz's Avatar
    Join Date
    Feb 2007
    Location
    MA
    Posts
    92

    Default

    if you manually open the zone valve it should start circulating if the others are working.. (you have air in the system)

  9. #9
    DIY Member coz's Avatar
    Join Date
    Feb 2007
    Location
    MA
    Posts
    92

    Default

    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. #10

    Default 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. #11
    Plumber Cass's Avatar
    Join Date
    Nov 2005
    Location
    Ohio
    Posts
    5,984

    Default

    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. #12

    Default

    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.

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •