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  1. #1
    Join Date
    Jan 2013
    Posts
    23

    Confused Bosch Therm 660 EF makes horrible noise in simple radiant heat system

    Hallo

    Need help

    Any idea why my tankless bolier makes this horrible clanking noise when used in my radiant floor system?

    When I run tap water thru it (using isolator valves) everything is fine but as soon as I switch to my closed loop system it makes this noise (see video)

    I have 4 loops about 200' each. Taco 10 pump with check valve, Extrol #30 tank, B&G air separator and its a very simple 1 zone system.

    http://www.youtube.com/watch?v=zM6tp...YfVJspXQWhL-2w

    Im pretty sure there is no air in the system. I ran each loop for a long time until there was no bubbles. Tried different coolant pressure but I dont know what to do. Needle on the pressure gauge shakes when this noise occurs.

    Willing to try any suggestions

    Thanks

    Greg
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  2. #2
    Join Date
    May 2012
    Location
    Upper Michigan
    Posts
    3,588
    Wow that sounds bad, id call a pro to have them look at it.

  3. #3
    Join Date
    Jan 2013
    Posts
    23
    Im asking PROs here

  4. #4
    Join Date
    May 2012
    Location
    Upper Michigan
    Posts
    3,588
    For one I can't give an answer by hearing a 10 second video it's hard to tell the area the noise comes from. We don't give DIY advise here, it's right in the rules that you read, if I do I get in trouble.

  5. #5
    Join Date
    Jan 2013
    Posts
    23
    I read the rules and it said to post questions in AOP section

    If you cant answer then whats the point?

    I am unable to pinpoint the area of the noise. Unit is pretty small and theres no way of knowing where it as its resonationg thru the whole unit

    Greg
    email addresses are not allowed in pot, please put it in your profile, thank you.
    Last edited by beenthere; 01-16-2013 at 09:57 PM. Reason: email

  6. #6
    Join Date
    May 2012
    Location
    Upper Michigan
    Posts
    3,588
    Sometimes It boils down to the question, assisting someone working on gas fired equipment can be dangerous so the owners of the site don't want the liability.

    What your saying though is when the unit fires making domestic water it's quiet but when you heat the floor it makes that noise?

  7. #7
    Join Date
    Jan 2013
    Posts
    23
    yes

    Works fine when I pass tap water thru isolator valves and when I switch to the loop it makes the noise.

    Thx
    Greg

    PS. This system was not installed by me. It was done by a certified HVAC friend of mine.
    He is trying to help me but I have a feeling he does not know what is the cause so Im trying to get some pointers here.

  8. #8
    Join Date
    May 2012
    Location
    Upper Michigan
    Posts
    3,588
    I'd like to help but it's a strange situation, one of them things were you have to be there. The difference is a pump is pushing water through, but I can't think if a reason why it would do that. We do have a contractor map here to find good people in your area if that helps

  9. #9
    Join Date
    Jan 2013
    Posts
    23
    u saying it would be better if the pump was after the boiler?

    Can these Taco pumps go bad? I bought it new. It probably got 1 or 2 hrs on it
    Sometimes boiler doesnt want to turn on like theres a insufficient flow

    Greg

  10. #10
    Join Date
    May 2012
    Location
    Upper Michigan
    Posts
    3,588
    Typically the pump is on the supply to the floor after the air vent, the slightly lower pressure lets the air out. Did you try hooking a hose on the return or loop and purging water out while letting water through the boiler? That would simulate how the domestic works but put the pump out of the equation. It's a long shot but it may tell you something. I wouldn't start changing parts or anything, a pro in your area might easily find the issue and save you money. If you have antifreeze what I just told you is a bad idea also because you will lose it. If I was in your area Id be up for the task, I like to fix weird stuff like that.

  11. #11
    Join Date
    May 2012
    Location
    Upper Michigan
    Posts
    3,588
    Is the pump backwards?

    It looks ok I think

  12. #12
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    Looks like the flame in the sight glass is jumping around and there's plenty of orange in there.

    Any chance the pump is flowing backwards? That sound has to be the pump if it doesn't happen when making hot water. Sounds like really bad cavitation.

    What is hooked up to the the return service valve? Is there no permenant make-up water or auto fill valve? The PRV should be piped down to near floor level.

    Totally off topic... but what do you ride? Motocross? or sportbikes?

  13. #13
    Join Date
    Jan 2009
    Location
    Keokuk, IA
    Posts
    5,520
    Is't it preferred that the air sperate be at the highest point in the loop? So the expansion tank and seprator ideally would be located next to the boiler so the seperator is just above it.

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