Need Help Btu's for oil base board hot water

Brad White

Glenn, Norm and Joe.

Doing a heat loss calculation yourself as Norm suggested is in my opinion the best way to be invested in the process. It is not difficult but it does take some time and thought. Once you have that under your belt, you have a basis of comparison for any improvements you want to make or for your next house.

Glenn's thinking is about where mine is, that 94K will be about double what you would expect to need for a house that size, insulated as you described and assuming a zero or single-digits outside heat loss as typical for central Mass. The 45-50,000 sounds right for a house built in the 1970's or later but in saying that does not negate doing a heat loss calculation. An older house, say one over 100 years, could well be 10-15% higher even if retro-insulated.

If you are up or down 10% from what otherwise is a guess, that could mean a boiler size increment which could be 20-25% more than you need... this is why an appropriate heat loss calculation pays dividends for the life of the system.

Now, the old boiler may have had an output of 94,000 and maybe that was once needed. But with proper sealing and insulation since, you would never capture that efficiency in a new system. This is your opportunity.

Acanfield

Btu's for new boiler?

We were told we need a new boiler for our 2,000 sqft.home in central MA. We have good insulation,pretty tight house.What should the BTU's be on the boiler? One company said 94,000 would be fine. Our present boiler doesn't say.
Help!

Couderay

Heat Loss

Have a heat loss done by a reputable heating contractor. This is very important in sizing the boiler's BTU's. Also will the old base board be staying??

Norm Harvey

I found this free heat loss calc in a google search.

http://www.acdirect.com/spacepak2/spacepakapp.html

you can give it a try and get an idea of what your heat loss may be.

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Glenn Sossin_2

94,000 sounds about twice

what you need. Unfortunately, this is a normal occurrence. You said the house had good insulation, and was pretty tight.

I've been doing heat loss for longer than I care to say, but I came across a chart that Weil McClain put out approx 25 years ago. I use it as a second check on my computer heat loss numbers. I have always found it be useful. See attachment.

Based on what you said, I would expect your heat loss to be somewhere + / - 45,000 - 50,000 btu's.

Keep in mind, most boilers are dumb devices. You tell it you need heat, it turns on full blast regardless of the outdoor temperature and the heat load of the calling zone. Oversizing it is not a good thing. It will cycle excessively, costing you real dollars and lower the life span of the equipment.

Consider using an outdoor reset control. It should have a measurable effect on your fuel bill.

Ask whom ever told you 94,000 btu's how they came up with that value. huminah- hummminah uhh huminah its a good number. If you really want to know, have someone do a heatloss for you. Bet you a donut, 94,000 is 50% higher than the actual heat loss.

There are other factors to take into account - how do you get your domestic hot water. Some contractors will increase the size of the boiler to try and accomodate DHW loads.

Check out the chart - its easy to use.

Hope this helps you.

Glenn

[Deleted User]

Before we go and jump the gun- did the company that said 94,000 BTU/h tell you that was your home's heatloss or that a boiler that size would work? If you're having an oil fired boiler installed, a three section boiler - the smallest size for traditional single pass american made cast iron boilers - is usually more than needed. I just installed a Peerless 3 section in a home that only required about 60,000 BTU/h. If that's all the customer wants or can afford that's the best a contractor can do. I've noticed in the past that alot of times on this website assumptions are made without all the facts being known. I would hate for that contractor to lose a potential job because someone insinuated a calculation was not done. If you're unsure- ask to see the numbers room by room.

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