sizing boiler?

[fat eddy]

I would prefer to undersize a piece of equipment although slightly.

[beenthere]

Do a load calc, and check the output of your baseboard to make sure the baseboard atleat matches your load, then get a boil that has an IBR output to match your load.

Again thats I B R output, not DOE output, a mistake made by many.

[sweet]

3000 sq ft @ 30btu/= 90000 btu heatloss devided by 580 x .8= 124 IBR rating thats gonna be quite a bit larger than 100000 btu boiler. Do a heat loss calc. and size it accordingly for design temp. This should give ample wiggle room and efficiency. I also think 580 is a closer number for output of basesboards ( you are talking about fin tube convectors, correct??)

[casturbo]

Originally posted by Noel Murdough
AND I stand by what I said.

I spend a major portion of my day explaining to homeowners of contractor installed equipment why the thing short cycles so badly, why condensation is running out of the chimney cleanout, and why controls die so young.

You do what you want to, in your new construction jobs.

Noel

Too bad I do ZERO new construction jobs. I do mostly repair work and replacement jobs where teeny boilers in large homes are thrown out. It's routine, sorry bud.

A SLIGHTLY oversized boiler will not short cycle badly, will not condensate, and will not shorten controls. In reality, controls last longer, circ pumps last longer, and the boiler itself lasts ALOT longer. LET ME REPEAT...SLIGHTLY OVERSIZED I SAY AGAIN, NOT GROSSLY OVERSIZED. Remember, I can always SLIGHTLY drop nozzle size on a larger boiler to compensate, you CAN'T put in larger nozzle in a small boiler. Think long run and you'll see what I see everyday.

[jrc2905]

I guess I will have to do a heat loss calc, I was hoping for an easy way out in using the baseboard method.
Is there a formula to use to adjust baseboard water temp to match heat loss?
I might try to get homeowner to go for one of the new products that use outside temp sensors and mixing valves to adjust the water temp of the baseboard

[hydronicsman]

I detest math so I play with the load calc baseboard output numbers to see what water temps match the existing linear feet-if you know you have too much bb for the load at 580 BTU per foot, drop the "output" a hundred degrees and see how it works. Clear as mud?

I use IBR net w/ steam sizing. Modern hot water baseboard really doesn't see the 15% pickup loss. I daresay IBR may be even a little antiquated . DOE is better suited here, especially when these days most jobs get an indirect water heater placed right next to the boiler-pickup loss is nil.

By all means check out outdoor reset. With oil prices, why run the boiler wide open on those 40-50 degree days?

[casturbo]

Originally posted by hydronicsman

By all means check out outdoor reset. With oil prices, why run the boiler wide open on those 40-50 degree days?

How much do these reset controls really save? Any real life test results avaiable? My understanding is they save less than 5% on the heat bill, but cost hundreds to buy and install. Anyone?

[millerman]

Originally posted by casturbo

Originally posted by hydronicsman

By all means check out outdoor reset. With oil prices, why run the boiler wide open on those 40-50 degree days?

How much do these reset controls really save? Any real life test results avaiable? My understanding is they save less than 5% on the heat bill, but cost hundreds to buy and install. Anyone?

Beckett's HeatManager is product that seems to work pretty well. We have installed some and have had no complaints.
They claim 10-20% reduction in fuel consumption and work with oil, gas or propane. http://www.beckettcorp.com

[beenthere]

We do most retro fits, and always use the IBR rating of the boiler, many times the 15% isn't there, but on alot of older houses it is.

Swat, if I had a house that required 90,000, I'd use a boiler with an IBR rating of 90,000, and that would be about a 113,000 DOE rating. In a retro fit.

New construction would depend on basement finnish.

[wallynut]

Do not oversize like some idiots have mentioned, You will find multiple firing rates on three and four section boilers { if cast iron} that will fall into proper Net BTU Water. Go with Heat load of House with or without domestic hot water added.
Old school go a size biger zust in case. This is a NO NO.

[beenthere]

I saw the advertisement on the heatmanager, but it seems like just a timer, with no reset ability.

[sweet]

I installed a BB heating system in my house. 81% cast iron boiler,about 1800 sq ft poor insulation. Installed Tekmar 260 controller with outdoor reset, dropped haeting bill 25% in one month of use, Im sold on installing Outdoor reset on boiler installs.

[fat eddy]

A reset function is one of the most energy efficeint that you can add to a system, done properly and controlled by a PID loop it is the single most effective control you can spend money on to save energy. it is commonplace in larger systems.

[hydronicsman]

You can look at it this way: Spend the few hundred for reset now, and save fuel-whether it's 10% or 30% (mileage may vary depending on the human impulse to crank the thermostat).

Or:


Give your fuel supplier that few hundred EVERY year till you die.

I think I'd rather keep the money

Look at the side bennies: systems are quieter because expansion noises are minimized-pipes aren't getting shocked all the time with 180 degree water. House temps are more even and comfortable. You are reducing the already low pickup losses from piping even more, etc.

[jrc2905]

The out side reset systems I looked at were very pricey in the $XXX range. Is there a more affordable unit I should consider. The concept made sense to me because it elimiates temperature spikes.

(No pricing, due to site rules )

[Edited by jultzya on 10-29-2005 at 02:10 AM]

[sweet]

There are some variables. Modulating boiler ,atmospheric,primary/secondary. It depends on the type of system you have or want. XXX sounds high,for some decent fuel savings it seems you could get by with something a little less. Regardless, check your options Tekmar has always been very helpful and have stood the test of time.

[Edited by jultzya on 10-29-2005 at 02:12 AM]

[ps]

I don't mean to be a PITA, but has anyone noticed that jrc appears to be a contractor? He seems eager to learn (always a good thing) but the questions he's asking are basic and I for one would not want to be his first installation unless accompanied by an experienced co-worker.

P.S. - Use I-B-R rating for retrofit and/or DHW applications. Extra 15% will account for most discrepancies in heat calc. Reset controls are worthwhile but proper near boiler piping must protect boiler from thermal shock.

[jrc2905]

Hey ps not that I feel that I have to explain myself to you or anybody else, but I am not a contractor, I wish I was. I service AC and oil heat systems due to a medical situation that prevents me from heavy work. That being said I have some people (friends) who ask for a boiler install and if they can lug the boiler into their house I will do the piping and electrical.
Why do I ask, because the vast majority of AC and heating installs that I see doing service leave a lot to be desired and I find the information here very interesting and
helpful.
When I put a system in I read the instructions that come with it and that is how I install them because I think the people who design the system might know what is right. I just wanted to know if I was going to waste this guy’s money on a larger system that was limited by the baseboard btu out put.

So do not worry about me, worry about yourself and please do not take it personal. (BTW ps how many installs have you done?)

[Edited by jrc2905 on 02-17-2005 at 01:15 PM]

[ps]

jrc - I won't take anything personal and I hope you don't either. I wasn't trying to discredit you, only trying to understand.
I agree that there are a lot of systems installed that are less than optimal - and I actually give (gave) you credit for trying to get as much info as possible. Good luck with your friends' job.

BTW - There are also good forums re boilers and HW systems at Heatinghelp.com and boilerroom.com.

P.S. - I have been in the business for 15+ years and haven't kept count. It really wasn't personal, I am always concerned with quality installations and the reputation of the industry in the eyes of the public - something you seem to understand, also.

[Edited by ps on 02-17-2005 at 01:26 PM]

[casturbo]

Originally posted by jrc2905

.... because the vast majority of AC and heating installs that I see doing service leave a lot to be desired and I find the information here very interesting and
helpful.

You can say that again, I do mostly repair work but do some residential A/C and oil boiler rated work too. General installations for the most part are nothing more than average, with alot of systems downright poor in their layout and installation. It appears everything is governed by price, so much that homeowner needs are for the most part, totally neglected or basically DEAD last on the list of concerns. What I really don;t like is telling the HO why they have so many problems or what a good installation with good equipment could do for them. It really pisses me off....sorry for the venting.