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baxi luna 310fi

i have domestic water working fine but the heat portion will lose pressure after a day or so. I fill up to 2 psi and it will work. Come back next day and its down to nothing and not cycling to zones. Have replaced the over pressure valve twice (thought i got a bad one). Heat exchange, (thought it was leaking). I put a bucket under to catch the over pressure and it seems to slowly leak out over the day. My next idea was to replace the expansion vessel but that's kind of involved. What you guys think?

Comments

  • Aaron_in_Maine
    Aaron_in_Maine Member Posts: 315
    I would just add a expansion tank to the system piping and leave the one in the boiler alone. I have done this a few times that design is crap.
    Aaron Hamilton Heating
    [email protected] yahoo.com
    (207)229-7717
  • Tom_133
    Tom_133 Member Posts: 821
    Aaron is on the right track. You need a system side expansion, but because of the internal 3 way valve you also need to swap the internal if it's bad. And it sounds from your description like its bad. The three way valve isolates the domestic side from the heating side so adding just the external won't help during hot water production. On the heating side the internal tank is not sized for carrying the heating load for long and they're expensive so best to add the external to prevent future problems.
    Tom
    Montpelier Vt
  • stevpauley
    stevpauley Member Posts: 4
    Ok, that sounds great. Since my DW is working fine, can I just add the new expansion on the outside of the unit? On the main line into or out of the box? that internal tank is buried deep inside and I don't want to disassemble it.
  • Tom_133
    Tom_133 Member Posts: 821
    I guess you can try it. Keep in mind if you have zone pumps you should install tank before them most likely in the bottom of the air separator. If you have zone valves and no external pump install it on the return, because that means the boiler pump is supplying flow and psi to the supply and you don't want to cut that down with an expansion tank.
    Tom
    Montpelier Vt
  • stevpauley
    stevpauley Member Posts: 4
    ok, I have four zones without pumps. There is one external pump which circulates for all zones, depending which one is turned on. So if I understand I would put it on the return line since the external pump is on the supply line.
  • Tom_133
    Tom_133 Member Posts: 821
    No just install it before the supply pump, if you take a pic and post it that would help. Remember to pump away from the expansion.
    Tom
    Montpelier Vt
  • stevpauley
    stevpauley Member Posts: 4
    sorry its been awhile, have been out of town. here are some pics of the plumbing and such. Big red pump is the main circulation pump for all zones depending on which one is selected on.
  • Tom_133
    Tom_133 Member Posts: 821
    We are going to need to see a pic or two from further back. Can't really tell what's, what or where.
    Tom
    Montpelier Vt