Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Oversizing energy waste....

kcopp Member Posts: 4,386
I went Friday night to look at some gas piping for a job...
2100 sq ft house, Tri-level, split level ranch. had a Weil Mclain GV-5 (140k input) running baseboard to a 50 gallon indirect and about 50' of hot water baseboard... criminally oversized boiler.
Anyone have some thoughts or a study as to how to figure the waste associated w oversizing a boiler?


  • Maybe they use a lot of hot water?
    If you can wait until the design day, when the perfect size boiler would run constantly, then a timer on the boiler would provide the percentage of actual run time to the ideal.
    Do they have outdoor reset, and combustion air?--NBC
  • Aaron_in_Maine
    Aaron_in_Maine Member Posts: 315
    Everyone that posts on here has seen this. I serviced a 1000sqft ranch that had a 7 section HB Smith boiler running 1 zone of heat and hot water off of a coil. :o
    Aaron Hamilton Heating
    ahheating@ yahoo.com
    RJMCTAFO Member Posts: 113
    Yep. The worst I have seen is an 1100 sq. foot ranch with a 3 year old Biasi B10-6. The plumber said they don't have to worry about it being big enough to put heat in the basement.
    I said they could heat their house and the neighbor on either side.
  • kcopp
    kcopp Member Posts: 4,386
    So great... is there either a rule of thumb or a formula to determine how much efficiency they lose by having a boiler so oversized....?
  • KC_Jones
    KC_Jones Member Posts: 5,692
    Is it only the wasted fuel, or potentially wasted fuel? What about equipment longevity? If it is cycling incessantly doesn't that shorten equipment life? That would be almost impossible to figure out, but in my opinion it matters. Tell someone they will save a couple dollars a month on fuel they don't care, tell them they will need to replace the whole thing more often and they might care. Wait no they won't they want it cheap no matter what. Didn't mean to hijack this just thought that was another aspect of waste with respect to over sizing.
    2014 Weil Mclain EG-40
    EcoSteam ES-20 Advanced Boiler Control
    Boiler pictures updated 2/21/15