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  1. #1
    Join Date
    Nov 2008
    Location
    ohio
    Posts
    10

    Running a heat pump and oil boiler

    Recently replaced my central air with a Trane heat pump. I would like to take advantage of the savings the heat pump offers to heat the house and save some fuel oil consumption.
    My boiler is hot water radiant base board with pipes in the attic. I would like to run the heat pump with outside temps in the mid 20's or lower but have concerns about the pipes freezing in the attic.
    I would like to run the circulating pump on the boiler and the only way I know how to do this is to turn the tstat for the boiler up and lock out the Honeywell R8184 Protectorelay to keep the boiler from firing and the circulation pump running.

    Would this cause any harm to the boiler system or be a safety issue?

    Vaillant Boiler with Beckett Burner

  2. #2
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,048
    One problem with doing that. Is that it will lower the boiler temp lower then what the basement temp is)or what ever room teh boiler is in).
    This will cause condensation in the flue passage ways, and can do harm to the boiler when the burner does run.

    Next, it will also increase the amount of heat, your home needs, since the water flowing in the pipes will also cool the baseboards to a temp lower then the house temp.
    It may also cause condensation on the baseboards.

    Your contractor should know how to connect the thermostat for the heat pump to use the boiler as aux heat, so that it runs in conjuntion with the heat pump at lower outdoor temps. And help prevent pipe freezing.

    Did they install electric aux heaters in the heat pump.
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  3. #3
    Join Date
    Nov 2008
    Location
    ohio
    Posts
    10
    beenthere, thank you for taking the time to reply.

    There are 15kw aux heaters installed in the air handler. Did this with the thought of eliminating boiler at some point. Feb of 2008 filled the oil tank and the cost of fuel oil was $3.69 per gallon and fuel prices seemed to be going up all summer. When I filled the tank in Nov. the price was $2.88 a gallon. My electric rates are .097kwh so when the oil rates rise again I might just drain the boiler next winter and run the heat pump only. Using the heat pump so far this year I have cut my fuel oil use in half but in Jan. and Feb I expect to have to use the boiler more.

    I was just trying to cheat the fuel oil co. out of a few extra days of fuel oil use.
    On those days when the outside temp is 25 the attic temp will run around 32 and thought about running the circulating pump on the boiler as a little insurance or peace of mind against freezing.

  4. #4
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,048
    The water won't actually freeze until its temp reaches about 28°F.
    Varies with the conditons of your water.

    Draining the boiler system, will work.
    But, if you intend to ues it if electric rates go up. The circ may seize from being dry, depending how long it set drained.
    A better way, may be to have hydronic antifreeze with inhibitors added to the boiler system, to give you freeze protection down to 10 or 0°F.
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  5. #5
    Join Date
    Sep 2002
    Location
    Northeast Ohio
    Posts
    4,842
    Quote Originally Posted by beenthere View Post
    The water won't actually freeze until its temp reaches about 28F.
    A better way, may be to have hydronic antifreeze with inhibitors added to the boiler system, to give you freeze protection down to 10 or 0F.
    Most likely the best fail safe protection in this case.
    A good HVAC tech knows how, an educated HVAC tech knows why!

    DEM


  6. #6
    Join Date
    Nov 2008
    Location
    ohio
    Posts
    10
    That is an option I had not thought about and like.

    It would allow me to test the performance and my satisfaction with the heat pump at lower temps.

    Then in the future if oil prices keep rising faster than my electric rates I will be able to make a better decision as to which heating system to use.

    Thank You

  7. #7
    Join Date
    Aug 2007
    Location
    MN
    Posts
    2,677
    you have boiler lines running through the attic? Why is that? could they be drained and capped down below? Never seen boiler lines in a attic
    You can't fix stupid

  8. #8
    Join Date
    Nov 2008
    Location
    ohio
    Posts
    10
    That never made any sense to me either but they are up there. Then again when the boiler was replaced the people who installed it ran the plumbing or just used the existing plumbing which would not allow you to remove the top of the boiler to clean it. I lived here 15 years and had the boiler serviced yearly and no one ever mentioned that. Finally a new fellow I called to replace the pressure reducing valve brought that up. I did, with great effort force the top off, then made some modifications to allow its removal. What a job it was to clean , but I learned a lot.

  9. #9
    Join Date
    Sep 2002
    Location
    Northeast Ohio
    Posts
    4,842
    Not sure where in OH you are but in the Youngstown Metro area there are a ton of systems with piping run overhead in the ceiling. Real nightmare when the boiler goes down and no one discovers it until stuff starts to freeze up
    A good HVAC tech knows how, an educated HVAC tech knows why!

    DEM


  10. #10
    Join Date
    Nov 2008
    Location
    ohio
    Posts
    10
    Today the outside sensor on my heat pump says it is 17* outside. It is a bright sunny day and sensor I mounted in the attic and it says the temp in the attic is 35*. I turned the tstat back on the boiler and am running the heat pump. This is when I would feel like running the circulation pump on the boiler would be an added safety measure against the pipes freezing.

    I have the heat pump set up to switch to aux electric heat at 10*.

  11. #11
    Join Date
    Nov 2008
    Location
    ohio
    Posts
    10
    heaterman, I am located in Dayton. The reason I knew the circulation pump would run with the burner locked out is a few times I had the fuel oil gel and no heat. I asked the tech about pipes and he told me about the pump running to help prevent that.

  12. #12
    Join Date
    Feb 2003
    Posts
    1,996
    go with anti-freeze. Crazy to remove the boiler. Sounds like it gets cold enough that you still might need it. Are you sure you 're gonna save with the HP and electric strip? If your duct work is not well insulated, it might be you warming the attic up to 35.

  13. #13
    Join Date
    Nov 2008
    Location
    ohio
    Posts
    10
    The duct work runs in the slab. It was there for the A/C unit I replaced.

    The bright sun on the roof is what is causing the temp in the attic, on cloudy days or at night the outside temp and attic still vary 5-10*.

    My electric bill to run the A/C in the summer are far less than running the boiler for heat in the winter so I am sure that until the aux heat kicks in on the heat pump that it is cheaper to run the heat pump.

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