Page 1 of 2 12 LastLast
Results 1 to 13 of 18
  1. #1
    Join Date
    Sep 2010
    Location
    Boston area
    Posts
    7

    Frown How do you supposed to size boiler?

    So far I had three installers came to give quotes on new gas HE boiler. Regarding sizing, one said you didn't need to do heat loss analysis and just size based on the current one, the other said he'll come back and do it when I end up going with him. The third one, initially said that it's based on the current one's input BTU. When I argued with him saying that we have no idea if the current one is correct size, he decided to go around the house and do it. But it wasn't what I expected.

    He just went around and looked at the radiators and baseboards. Wrote down the size of them and calculated the gross radiated heat from them. From there he calculated the BTU for the boiler, which happened to be the same as the input BTU of the 30 yr old, current boiler.

    The heat loss analysis that I know, and expected him to have done is looking at the size of the walls,ceilings, floors, windows, roofs and etc and how well house is insulated etc. From that approximate their heat loss for the coldest winter temperatures in our area. There are a number of online calculation sheets you can use for this. When I did that it came out to be about 50% of what he recommended The total radiation output of your radiators that this guy did is just what your heating system can output in maximum not what your house needs to keep the desired temperature in your house on the coldest day of the year. Heat loss is heat loss not miximum heat capacity of your radiators, isn't it?

    I didn't even bother to argue him about it but am I missing something here? What do you professionals do to size boiler for your job?

    The other question that I have is how big of price difference there is, let's say between 140k BTU Alpine vs. 110k BTU Alpine? He hinted that it won't be that much therefore sizing is not important- a few hundred dollars? but I have suspicion that it will be more than that. Can any body answer that?

  2. #2
    Join Date
    Jan 2008
    Location
    In the work truck
    Posts
    2,945
    Keep looking until you find a contractor you are happy with and trust.

    Price is not something i can help you with as you get what you pay for ( that depends on who is installing it etc.)
    Gotta have the right tool for the job!

    Where is all the stuff MADE IN THE USA?

    "Thats what we do Troy. Incredible, Invisible, Imbelivable things. We are an Unseen, Unknown, Unvincible fraternity of craftsman.."

  3. #3
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    66,817
    We don't talk prices here.

    You are correct that the homes heat loss should be calculated, and the boiler sized to that(unless its a steam boiler, then it is sized to the radiators).
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  4. #4
    Join Date
    Nov 2007
    Location
    New Jersey
    Posts
    110

    boiler sizing

    Initial purchase price won't be that much different between the two sizes but, and this can be a big but, the more oversized the boiler is the more burner shortcycling you'll have. That translates to lower efficiency of the system.

  5. #5
    Join Date
    Sep 2010
    Location
    Boston area
    Posts
    7
    I didn't mean to discuss the boiler prices themselves but want to feel for the price difference between different sizes in general. If that's still no no, I'm sorry. Now that I think about it I can just google them and find out.

    Beenthere- you mentioned that steam boilers are sized to radiators. Is that because steam boilers cannot be modulated?

  6. #6
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    66,817
    Quote Originally Posted by safetrip View Post

    Beenthere- you mentioned that steam boilers are sized to radiators. Is that because steam boilers cannot be modulated?
    With a steam system. You MUST have a boiler big enough to generate enough steam to fill all the boilers. Or you'll end up with only the first few rads getting hot, and the rest of the house cold.

    Takes a lot of steam to fill the pipes and the rads.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  7. #7
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    66,817
    And we don't take price differences either.

    Doesn't matter what someone on line will sell them for. Its what your contractor sells it for that counts. If you want him to provide warranty labor on the boiler. He has to charge what he has to charge.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  8. #8
    Join Date
    May 2002
    Location
    MEDIA PA
    Posts
    1,361

    Do a heat load

    they choose the boiler by

    Getting the SMALLEST boiler that covers the load on the coldest day

    Use the lowest water temperature ( in this case a lot of radiation is good)

    BUY the highest efficient boiler

  9. #9
    Join Date
    Sep 2010
    Location
    Boston area
    Posts
    7
    Quote Originally Posted by Big View Post
    they choose the boiler by

    Getting the SMALLEST boiler that covers the load on the coldest day

    Use the lowest water temperature ( in this case a lot of radiation is good)

    BUY the highest efficient boiler
    That's exactly what I'm trying to do but I cannot find any installer think in that terms. I had my 4th installer came to give me a quotes. When asked about heat loss analysis, his answer was the same. He'll count the total capacity of the radiators not manual J. He said that manual J only applies to new construction not when replacing existing boilers. Does this make any sense?

    All of these installers got A+ on BBB, great reviews on ServiceMagic or references and have been around for a while. It seems to me that manual J is just not in their genes. Very frustrating.

  10. #10
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    66,817
    You should screen them over the phone, so you don't waste your's or their time.
    if they say they don't do/need to do a manual J. Say thank you, I'll call someone else.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  11. #11
    Join Date
    Jul 2001
    Location
    Gold Coast of Connecticut
    Posts
    4,545
    Do you make hot water with this boiler as well?

    If so how big is the tank. It is hard to find a residential home that cant run with a 100K output boiler. Most times the water load needs more BTU's than the home if you have 3 full bathrooms.
    Aire Serv of SW Connecticut- Gas heat, dual fuel and central a/c systems installed and serviced

  12. #12
    Join Date
    Sep 2006
    Location
    Leavenworth KS
    Posts
    299

    Smile Question

    I have a question is this hot water or a steam system? You have had several people out that measure your system like the steam way. You are located in the northeast where the skill levels should be high. Maybe post some pic's that could help. Boiler and rad's would be great.
    Mike

  13. #13
    Join Date
    Jul 2004
    Location
    Massachusetts
    Posts
    6,826
    We do heat load analysis on every job, boiler, furnace, AC, except for steam boilers. For them we have to size to the connected load or radiators. Too small, you won't heat the rads and hence not heat the home. Too big and you'll not heat the house due to short cycling and potential priming and return problems. Proper sizing of steam boilers is almost a lost are for most. In Boston area, 99% of the boilers installed are done by plumbers who wouldn't know a heat load analysis if they had one fall on their heads. I'm a Master Plumber but we speicalize in doing it right the first time, which means a detailed load analysis. We're never the least expensive but we are the most valuable, as you're finding out. If you're in our area, looks us up.
    If YOU want change, YOU have to first change.

    If you are waiting for the 'other guy' to change first, just remember, you're the 'other guy's' other guy. To continue to expect real change when you keep acting the same way as always, is folly. Won't happen. Real change will only happen when a majority of the people change the way they vote!

Page 1 of 2 12 LastLast

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Comfortech Show Promo Image

Related Forums

Plumbing Talks | Contractor Magazine
Forums | Electrical Construction & Maintenance (EC&M) Magazine
Comfortech365 Virtual Event