Boiler Size????


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Old 03-01-12, 10:08 AM
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Boiler Size????

Hi Folks,

My 1979 Weil-Mclain gas-fired forced hot water boiler will be replaced this spring, and I am confused about what size to replace it with—getting conflicting information. I am also confused about what the various numbers mean.

The exist Model EG-65 is rated: AGA Input-250,000, DOE Heating capacity—209,000, and NET I=B=R-183,000. One contractor wants to replace it with the same model/same size. Another contractor did a heat-loss study, telling me 80,000 over the phone, and indicating that it seemed low to him, but he cannot figure out what, if anything, he might have done wrong. Both contractors have done excellent work for family and friends, so it is simply a matter of what size is appropriate.

I did my own calculations using 2 detailed spreadsheets I found at a heating supplier’s website. One spreadsheet calculated size requirement based on heat-loss, and the other calculated it based on standing radiation. The sheets measured up well against similar offerings I found on-line, and I am confident that the info I put in is fairly accurate. My heat-loss requirement came to 93,000 BTU/hr. The standing radiation came out to 110,000.

The home is an un-insulated, original windowed (with storms), 1904 2-story colonial revival, 2,500 sq. ft. with an unheated basement and an unheated walk-up attic. The first floor has huge 3-column radiators, except for the kitchen—which probably originally had a cook-stove but now has a 3-tube radiator. The 2nd floor bedrooms have 5-tube radiators and the bathrooms have Burnham BaseRay cast-iron baseboard. The present boiler heats the house just fine, although is very expensive to run, costing almost $3000 of late, which includes a 50-gallon gas hot-water heater, 2 people living here.

Possibly of note: The basement is loaded with huge black-iron pipes breaking out into smaller pipes, with gate-valves, as if someone might have thought of zoning the system, or, perhaps, using the valves to balance it. (I have no interest in zoning it.) Also of note is the fact that in my 15 years here, I have never seen the boiler reach its high-temperature shut-off. It rarely gets much over 160 degrees.

It just seems like there is an awful lot of water to be heated up, and if the present, possibly/likely over-sized boiler does not get it all that hot—will a smaller one do it? I understand that many or most homes have over-sized boilers, but the difference between what I have, and what I think I might need seems a little extreme. Is there something simple that I am missing? I would hate to be cold….. My wife would kill me….

So, any thoughts on what size boiler would be greatly appreciate. Thanks.

KOT
 
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Old 03-01-12, 11:00 AM
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One contractor wants to replace it with the same model/same size.
Hello KOT,

Run. don't walk, as far and fast as possibly away from that guy.
It can never make any kind of sense, what so ever, to put in more boiler than there is radiation! No matter what, you don't need a boiler bigger than 110,000 DOE.


What's wrong with the old boiler?

If at all possible, it would be money good, to put the cash into insulation and related rather than a new boiler. That's really the best way to reduce heating bills.

The guy that took the time to do a heat loss, is the person i would want to hire, for sure.

Your present set-up would be a good canidate for a mod-con boiler.
The massive iron radiation and water content allows your house to heat with low water temps. That is great for efficiency with a mod-con boiler.
Also if you add insulation and what not over the years ahead, a mod-con can at least down fire somewhat to make up for its' eventually becoming too large.

IMO i'd go with the 80,000 guy and at least try and insulate the attic.
Otherwise if you are never going to insulate(bad ide), your 93,000 might be safer.

Just think abut what happens if the price of gas were to double in the years ahead... insulate!

Oh ya, are all those big black iron pipe in the cellar insulated?
If not... then that would be an easy place to start.

Peter
 
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Old 03-01-12, 03:10 PM
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... got my chips cashed in... set up, like a bowlin' pin... knocked down, it gets to wearin' thin.......
It's been said here previously, many times:

Insulation is fuel that you only pay for ONCE!

I agree, at the very LEAST, get up to R40 in the attic, minimum. Blown in cellulose is a good choice for attic insulation.

Start sealing up all the air leaks you can think of. Go crazy with this phase, it's IMPORTANT!

Spend the couple hundred bucks on a REAL energy audit which includes a 'blower door test'. It will identify the areas that will give you the most bang for your buck as far as sealing and insulating.

Do this BEFORE you replace the boiler!

Agree with Peter, cross the 'replace with the same size' guy right off your list. He doesn't care about you or your fuel bill, and he SHOULD.

Do your own heat loss calculation... again... you can download the SlantFin heat loss calculator here:

Contact Us - P.V. Sullivan Supply Co., Inc.

It's a 175MB download. You probably already have all the measurements done. Plug the info into the program. It will give you a number that is about 20% more boiler than you need, so do NOT add anything to it.

Basing the boiler size on the installed radiation is also NOT the correct way to size a boiler. Common practice back in the day was to install MORE radiation than needed. Size a boiler from this and you will be oversized, although it sounds like in your case, it's pretty close.

I have never seen the boiler reach its high-temperature shut-off. It rarely gets much over 160 degrees.
This is likely due to the fact that you have more radiation than you need. This being the case, what it means is that the system is able to heat the home with COOLER WATER, which is a fuel saver, and a good thing. (on the other hand... never trust a boiler gauge... never trust a boiler gauge... etc)

By the way, if your home were insulated and air sealed, you would likely be able to heat it with a 50K BTU boiler.

OH, one more thing... new windows RARELY if ever are worth the expense to make up significant fuel savings. Seal and insulate FIRST, and if the windows are in really bad leaky condition, replace them LAST. Don't let the window and door salesmen fool you!
 
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Old 03-01-12, 03:16 PM
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I know that 'rules of thumb' aren't always reliable, but here's one for reference anyway, to be used as a 'sanity check' only.

A big old leaky uninsulated home might require about 40 BTU / SQ FT to heat.

Average construction in the past 40-50 years might be around 25-35 BTU / SQ FT.

Modern homes built with energy conservation in mind can be as low as around 15 BTU / SQ FT.

My 50's built expanded cape at around 2000 SQ FT has an ACTUAL MEASURED heat loss of significantly under 60K BTU. (measured by 'clocking' my fuel oil usage and recording 'degree days' and doing the math) It is 'reasonably' well insulated (could be better) and air sealed.
 

Last edited by NJT; 03-04-12 at 08:38 AM.
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Old 03-01-12, 04:30 PM
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Agree with Peter and NJT. Air seal and insulate. Then size boiler for new, much lower heat loss. Smaller boilers have lower initial cost, can have greater overall efficiency due to less cycling losses, etc.

Any installer who simply replaces like for like should be shown the door. Immediately.

And you are a great candidate for a modulating-condensing boiler.

I wouldn't replace the boiler unless it is worn out or broken beyond reasonable repair. Spend the money on air sealing and insulating. Replace boiler later. In a house such as yours, a couple grand could easily cut the heat requirement by a third to half.

Like Trooper says about insulation being fuel you pay for only once, it is equally true that an oversized, inefficient boiler is something you pay for forever....
 
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Old 03-02-12, 06:41 AM
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Thanks to all,

Attic: The attic floor is the one thing that is insulated. Blown-in cellulose(??), enough that when the roof leaked into a bucket, the water would freeze.

Windows: I like my wavy glass, and the fact that I can open and close them with one finger, although I do get tired of changing window ropes. I may get better storms someday, but I'm keep the windows.

Insulation: Maybe someday, but I do like to tell people that my house has excellent ventilation.

Boiler problem--besides the fact that it is too big: I ignored for 15 years the fact that the sheet metal jacket was slowly rusting around where the return pipe went into the boiler--ignored it, that is, until the leak got so bad that it would not evaporate fast enough to hide the fact that it was something I should pay attention to.

The guy who did the heat-loss study for me was able to successfully get the pipe out and replace it just before Christmas, but it just started weeping again. I have no problem replacing a boiler that is 33 years old, leaking, and probably twice as big as I need.

So, if I need, for example, a 100,000 BTU boiler, which of the rating numbers equate to that? Output?

I have downloaded the Sullivan heat loss program, and will mess with it over the weekend. Maybe call the MassSave folks for a free energy audit, although I hear their private contractors are hit or miss as to whether they will actually do anything useful, other than try to sell you the easy stuff.

And lastly, what is a modulating-condensing boiler?

(Note: I have no desire to be fancy, or cutting-edge--We are in an Historic District--

Chelmsford Historical Commission Presentation

--and I like the house as it is.)

Thanks again.

KOT
 
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Old 03-02-12, 07:29 AM
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So, if I need, for example, a 100,000 BTU boiler, which of the rating numbers equate to that? Output?
Yes - the DOE rating should equal the calculated heat loss. Don't add any margin - it's cranked into the heat-loss programs.
 
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Old 03-02-12, 08:09 AM
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(Note: I have no desire to be fancy, or cutting-edge--We are in an Historic District--
Harmon still makes very good quality coal boilers.
Nothin fancy or cutting edge. Old and reliable.
Nearly centuries of use has proven the concept.


I think this one would be a perfect fit BTU wise:
Harman Stoves | VF3000 Coal Boiler


Peter


PS
Ii live in a Histericl Distric too.
I like cutting edge.
 
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Old 03-02-12, 03:36 PM
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Peter, I'm going to assume your post was in jest. So, I won't recite the problems with coal heating, e.g., coal dust, ash disposal, stench, turn-down, coal suppliers, coal storage, fly ash, etc. Well, I guess I did recite the problems.
 
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Old 03-02-12, 03:37 PM
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In this situation, then yes, it is time to replace the boiler. Historical district not a problem with modern venting. Can generally be placed somewhere unobtrusive. A major advantage to moving the boiler air intake and exhaust outside of the building envelope is that you are no longer using indoor air for combustion, which greatly reduces air infiltration into the home. Infiltration through leaks, holes, etc. can account for up to 30% of a home's total heat loss.

Get the MassSave free audit. Among other things, it will qualify you for other incentives, like the HEAT loan program (0% interest loan for high efficiency heating, solar, etc. see Mass Save HEAT Loan), and for weatherization rebates (air sealing and insulation). Last I heard the program was still contracted out to RISE Engineering. And yes, they will take advantage of the fact that they are in your house doing an audit to give you a contract with weatherization measures already spelled out. But you are under no obligation to use RISE. You can select from a variety of MA approved weatherization contractors and still get the various state rebates and credits.

You absolutely don't need a boiler with a DOE capacity greater than your standing radiation. IF you do some weatherization, you can easily cut the heating requirement by a third to half. Forever. If you really tighten up the place, you can also go with specific intake and exhaust ventilation to ensure proper air changes. All kinds of stuff out there for that, starting with simple high-efficiency bathroom fans designed for that.

Take the time to do it right. When shopping for contractors, take your time. Be thorough. Lots of knuckleheads out there.
 
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Old 03-03-12, 09:23 AM
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Folks,

The rule-of-thumb works for me--2500 ft at 40 BTU/ft comes out to 100K--sort of where I might be.

Re: the prospect of coal--there is plenty of it in my flower beds, from way back when.....

And--old v. new--I finally have added internet controlled thermostats both here at home, and at our little weekend getaway in York, ME. It is great to be able to crank the heat up before leaving, and to then arrive at a warm place.

Anyway, the SlantFin program came out to just under 60,000. I would consider my 3 calculations as follows (and I hope you can correct me or clarify, as needed):

SlantFin calculates out at 60,000

The other two spreadsheets I used are provided on Crown Boiler's website.

The Standing Radiation calculation is 110,000 BTUs--seemingly more than I need--and it might explain why the system never gets all that hot--it doesn't need to.

The Crown Boiler Heat Loss calculates out to 93,000. This spreadsheet includes, in addition to the usual stuff about doors, windows, and construction, inputs regarding the exterior footprint of the home, and entire outside wall heights. Thus--the 2500 sq ft. It also uses a gross volume figure, based, again, on the outside dimensions of the building.

The SlantFin calculates based on the inside dimensions of the rooms, which comes out to just over 2000 sq/ft. The large difference can be attributed to such things as:

1) We did not measure or include closets (except for the walk-in)--should we have?
2) We did not add in various built-ins, which go from floor to ceiling.
3) We did not add in the space taken up by a rarely used back stairway, which has doors at both the top and bottom--We did add in the doors as cold partition areas.
4) We did not include an unheated vestibule, though we did include the door as an outside door, and the wall as as cold partition.
5) Generally, wall thicknesses, both interior and exterior, would not be part of the SlantFin calculation.

In any event, I think my inputs are at least accurate, if not correct.

Another factor to maybe consider, and which I would appreciate comment on, is the fact that the existing system does not have an aquastat to maintain boiler temperature. Our work schedules and weekends away mean that the system is often starting from dead cold. Should we have the ability to maintain boiler temperature during heating season? How has the lack of it affected anything going on?

Am I getting any closer to figuring out an appropriate boiler size? If I forgo a high-efficiency model, should I/would I still save money on heat by having a properly-sized one?

Thanks again.

KOT
 
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Old 03-03-12, 10:47 AM
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Warm-start boilers are an incredible waste of energy. Cold-start is what you want.

Yes you are getting closer. I'd go with 60-80k.

Yes you would still save money with a properly sized conventional (fixed input) boiler. But...

a) the boiler is only the proper size on the design day of coldest temperature. By definition (and in a typical real year), that only occurs for a few HOURS each heating season (e.g., in a ~6000 hour heating season, design conditions occur for around 40 hours). Any time the outdoor temp is above design, the boiler is oversized. Think about fall and spring, for example. It's a lot of hours. Now consider what happens if you size the boiler to the existing heat loss and then do your weatherization. Oops. You just cut the heat loss by half and now your boiler is 2x oversized. That's why you do the building envelope work first, then size the boiler.

b) a modern, modulating/condensing boiler with an outdoor reset control will automatically change the firing rate and water temperature to match the heat loss of the moment. So it is basically adjusting its 'size' continuously. Same goes for envelope improvements. Lower the load, and the boiler ramps down.

You can also put outdoor reset and other controls on conventional boilers to achieve better efficiency using lower water temperatures, and varying differentials.

Many options from which to choose. That's why it's important to do your homework, which you are doing. Keep at it.
 
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Old 03-03-12, 07:15 PM
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Avoid rules of thumb. I am still amazed after all these years that people still take something as sizing a heating or cooling appliance so lightly as they will pay for that regrettable decision every time the unit operated the rest of the life of the appliance.
Do the heat loss and heat gain and do it properly.
I have seen many times info is not entered properly or not at all, use inflated numbers to be sure the unit is the size they thoughth it should be before they started the heat loss.
I was on a job site in Norfolk this past week where the heat loss was greater than the connected load. The radiation was 170k and the heat loss was 208k. The old boiler was 160k. The new boiler is a 210k. The reason for the job site visit was fuel bills did not go down with a mod/con and cast iron rads.
The cost should have gone down 50% if all was done properly. The old boiler was over sized and 30 years old and chimney vented.
 

Last edited by NJT; 03-04-12 at 08:27 AM.
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Old 03-04-12, 07:03 AM
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Update:

My SlantFin calculation is now up to a 67,000 BTU requirement based on the two rooms that share walls with the unheated vestibule--I neglected to add in cold-partition info, and based on a 6 ft exposed wall in a 1st floor bathroom that I forgot about because it has no window and the whole bathroom is actually a jog-out of the otherwise square building. I will continue to review and refine.

It goes up to 70,000 if I use a 75 degree differential rather than 70. It does get to 5 below here occasionally, but the charts for my zip-code indicate 0, and I used 70 degrees as a high point. Point taken from Xiphias that the only risk of being undersized would be the few hours a year when it gets that cold, and in any event, it tends to happen at night when we are only calling for 62-64 degrees anyway.

I think I might forgo dealing with MassSave. I just read kind of a horror story in a newspaper handy-man column wherein a home-owner had MassSave in and they told him about various building-code deficiencies barely related to the energy audit. Sort of happened to me years ago, when I was trying to get low-interest loans to rehab some urban rental housing. Next thing I know, the guy form the city is suggesting all this other work that a contractor friend of his would be happy to help me with. I showed him the door and got my own market-rate loans. There is just too much petty corruption to be bothered with it.

I know the house needs insulating, etc., but I can live without it. And frankly, I have also heard stories where homes needed painting more often after having too much insulation stuffed into the walls. The paint job on the house that was put on just before we bought in 1997 lasted 9 years. We painted in 2006 at $12,500, and it has a few years left on it. Not worth even the possibility of having to do it any more often.

So, my main issue now is what size—which I am fast approaching—and whether to go “high-efficiency”. The local utilities are offering $1,000 rebates for 90% gas boilers and $1,500 rebates for 95%.

KOT
 
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Old 03-04-12, 08:44 AM
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While I don't think that anyone can absolutely PROVE that this is the reason, but this is about the best hypothesis I've ever heard as to why boilers have been historically oversized... just some light reading while we are on the subject of heat loss and boiler oversizing.

Heating Help
 
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Old 03-04-12, 08:47 AM
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heard stories where homes needed painting more often after having too much insulation stuffed into the walls.
If I had to guess, and I do, I would say that the reason for this is with less 'ventilation' behind the siding, that there is moisture driving outward to the unpainted back of clapboards. Moisture drives through the wood and breaks the paint bond.
 
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Old 03-04-12, 10:11 AM
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Inadequate attention to vapor barrier and where in the wall assembly there may be a condensation point. Solvable problems.

I'm sure you recognize that "living without" air sealing and insulation will cost you a bundle for as long as you own the house. How much is "living without" worth to you, per year? $1000? $1500? You should at least do the simple air sealing to reduce infiltration. Totally DIYable. See
http://www.energystar.gov/ia/partner....pdf?03a5-e660

for starters. And/or check out the Taunton Press book Insulate and Weatherize.

As to boiler size. If you go mod/con (and I would certainly suggest that), you are looking at a 60-80k boiler. Some brands to consider, among many.

Triangle Tube Prestige Solo 60 or 110
Lochinvar Knight 80 (the WHN fire-tube model)
HT Products Munchkin 80
Burnham Alpine 80
Veissmann 100
 
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Old 03-05-12, 06:03 AM
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While re-checking the 2 heat-loss calculators I am working with, I noticed under a “notes” section in the Crown Boiler calculator the following note:

“If the house will be used intermittently during winter, add 20% to the heat loss total for quick pick-up.”

As I indicated earlier, our work schedules, as well as many weekends away, cause the heating system to often be working from a cold start. Add to that the likely-over-sized standing radiation, as well as much cast iron pipe in the basement, (which I will mention in more detail below), and the fact that the place takes a long time to heat up now, with a grossly over-sized boiler, and I am concerned about warm-up time. I would appreciate opinions on which might make more—if any—sense as a partial solution. (Please note that I am as interested in reasonable comfort as I am in being as efficient and thrifty as possible. I would be quite happy with shaving “only” 1/3 (or whatever) off of my heating bill, even if there were another 1/3 (or whatever) to be had. I need a new boiler, whether efficiencies and savings accompany it or not.)

I could:

1) Slightly over-size the boiler—but still be much smaller than what is there now.
2) Set it up to maintain boiler temperature so I am never working off a cold start.
3) Do both of the above

Comments appreciated.

Regarding basement pipes: I have approximately 175’ of cast-iron pipe sized from 1” to 2.5” caliper running all over the place, all un-insulated since I had the asbestos removed. Very warm unfinished basement when the boiler is running. I have found 1” fiberglass pipe insulation for a total of $450-, including $150- shipping—or perhaps a little less if I can find it locally. This includes no insulation for the many elbows, unions, and other fittings.

Am I correct in assuming this would be a good investment, notwithstanding the initial outlay? Is this insulation the appropriate stuff to use, or would pipe wrap be better?

KOT
 
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Old 03-05-12, 11:53 AM
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I have approximately 175’ of cast-iron pipe sized from 1” to 2.5” caliper running all over the place, all un-insulated since I had the asbestos removed.
When you write "1” to 2.5” caliper" do you mean this is the outside diameter of the pipe? If so, these are not all that large, probably 3/4 to 2 inch nominal pipe sizes. Yes, they should be insulated and yes, rigid fiberglass is far better than soft "pipe wrap" insulation. You can either use pieces of the soft pipe wrap on the fittings along with pre-formed plastic covers (available from the insulation supplier) or just leave them naked. You won't lose all that much heat from the fittings and it will keep your basement a more comfortable temperature.

IF you decide to oversize the boiler for quicker load pickup don't go any larger than your installed radiation.
 
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Old 03-05-12, 01:23 PM
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4) NEITHER.

There is already a ton of fudge (about 20-30%) in the Manual J heat loss calculation. Warm start is an incredible waste of energy. There is really no point in having a boiler who's capacity exceeds your heat loss. The occasional exception is when that size is too small to meet the domestic hot water demand even when using a priority control. There is even less point to having a boiler whose size exceeds the output of your standing radiation. You could have a nuke plant in the basement but the rads can only output what they can.

Fiberglass is very good. You might also price out Armaflex. Nearly as good, easier to work with, can be used on elbows and other fittings, less expensive.
 
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Old 03-05-12, 09:12 PM
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The pipe size is the black iron pipe size. The larger ones look to be almost 3' OD. I ordered the 1" thick fiberglass stuff locally today and will buy some sort of tape for the elbows and other fittings.

I guess I am looking at a boiler in the 70-100k range. I will discuss it with the kid that gave me the 80k number but seemed not all that confident about it.

Thanks to all. Will keep you posted on what I end up doing.

KOT
 
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Old 03-08-12, 07:51 AM
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Another thought:

My 50 gallon, glass-lined, gas hot water tank was installed in 1993. I changed the anode rod about 10 years ago and used to flush it out occasionally, but probably have not done it for 5 or 6 years. Point is-- I may be needing a new one soon.

Can a tubing bundle be added to a gas boiler after the fact if it was an option when the boiler was purchased? Is the answer the same whether discussing mod/con or plain old vanilla?

If I wanted to switch to domestic HW off the boiler, is the old tankless tubing bundle the way to go--or am I better off with a free-standing water bank type of thing that is effectively a second zone off the boiler.

Is there a simple calculation that will tell me how much bigger, if at all, a boiler should be to provide domestic hot water?

My thinking is to put in a boiler on the higher side of what I have been coming up with--say 100k-110k, put in a low temperature aquasat in case I eventually add HW to the system, and somewhat assuage my irrational deadly fear of being cold because my boiler is too small, becasue I made a series of errors using all 3 basically concurring sizing spreadsheets that I used.

Thoughts appreciated.

KOT
 
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Old 03-08-12, 08:57 AM
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You absolutely do NOT want a "tankless coil" in your boiler for domestic hot water. Using a tankless coil is only one step removed from heating your water in an open kettle on a wood-burning kitchen range.

Yes, you CAN add an "indirect" water heater at a later date. Very rarely is an upsize needed in the boiler as modern controls will give the water heater "priority" when it is needed.
 
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Old 03-08-12, 11:30 AM
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What furd said. A tankless coil (Trooper and others often call them 'thankless coils') requires warm-start, which as noted is an incredible waste of energy.

The required gizmo is called an 'indirect tank' or 'indirect water heater'. The come in many flavors and sizes. They act as their own zone. It is best practice to provide them with their own circulator. Proper control will allow 'priority' aka 'domestic hot water priority' aka 'dhw priority'. When the tank requires heat, the control shuts off the space heating and all output goes to the indirect. When done, space heating resumes. Typical DHW call duration is <20 minutes, so there is no drop in space temperature.

Boilers are not upsized for DHW generation unless the DHW demand is really, really large. Like "I want to fill my 200 gallon jacuzzi bathtub RIGHT NOW" large.

There are simple quantities you can use to play with boiler output and how long it might take to recover an indirect tank of a given size. Like water weighs 8.33 lbs. per gallon and it takes 1 BTU to raise a pound of water by 1 degree F.

Do try to get over your irrational fear. It will only cost you more money now and into the future. Even in a poorly-insulated house like yours, it takes a long time for the temperature to drop even a degree. The worst-case scenario is that an undersized boiler is running full out, the emitters are doing the best they can with the water they are given, and over the course of 8-12 hours your space temperature drops by maybe 2-3 degrees, if that. And during this time you are asleep. Under a blanket.

If for some strange reason you do find it undersized, then by all means do some insulation and air sealing, and like magic you won't be cold anymore, and your energy costs will go down.

Also recall that it makes ZERO sense to have a boiler bigger than the output of your standing radiation. That is the absolute upper bound.
 
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Old 03-10-12, 06:11 AM
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Well--the contractor who did the load study and came up with a number similar to what I did (note--he too used the SlantFin calculator) does not appear to have the courage of his convictions.


He is concerned that there is so much water volume in the system that a 70-100k boiler might not do the job, and/or will run non-stop to heat up the system. He proposes installing a Navien CH-240NG combination gas boiler and DHW heater.

Any comments on the appropriateness of this product for my situation would be appreciated.

Thanks again.

KOT
 
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Old 03-10-12, 06:54 AM
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IMO, it would serve you well to find someone that has a similar unit, in a house similar to yours and talk to them about how it works for heat and hot water.


Good Luck,
Peter
 
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Old 03-10-12, 07:34 AM
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I will discuss it with the kid that gave me the 80k number but seemed not all that confident about it.
does not appear to have the courage of his convictions.
If he's indeed a 'kid' fresh out of HVAC school, I can understand how he might be a bit anxious about making a big mistake. He doesn't have the experience to base his judgements on, and for him it would be a 'leap of faith'.

While that Navien does have a pretty extreme modulation ration ( as low as 20K ) my belief is that it will be operating at 25% or less than it's capacity for 95% of it's life. It would be akin to having a 500HP rod as your daily driver to and from the train station.
 
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Old 03-10-12, 11:54 AM
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A 60-80k modcon can do a reasonable dT across the boiler and handle a circuit with 20-30F temp drop. Say 100 gallons in your system not a huge big deal. This is actually very common and an ideal application. In many applications where system volume is small (e.g., fin-tube baseboard, radiant), buffer tanks of 20-50 gallons are routinely added to improve performance.

The idea of a modcon IS to run non-stop. It finds equilibrium between water temp, heat loss, and firing rate. In an ideal situation, it would turn on in November and turn off in April. It modulates to meet the demand.
 
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Old 09-21-12, 02:05 AM
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my situation is very similar, hope you are still there

My 1910 2500 ag ft also has the same weil-mclain eg 65 250000 BYU and all the big pipi in the basement. Mine is a late 80s and may be losing water so want to replace and downsize. Is really like to know what you went with. Ihave lots of cast iron hot water radiators. I only lived in the house one winter in Minnesota and it was much warmer than normal. Did not get a chance to observe cycle times but may have been 20 min on 30 off. I had to throttle back on the rads with theeir shutoff valves to keep temp sown to 65.
 
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Old 09-21-12, 05:29 AM
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I went with a plain-old-fashioned cast-iron gas-fired Burnham 206NIL, 164k input, 118k Net. It was not worth the extra $ to us to go exotic, and the very-important annual maintenance requirement was an expense and another thing to worry about that I did not care to deal with. And we only expect to be here another 5 years or so.

The new, smaller circulator would not get the water flowing to 2 sections of the system (bathrooms) that have Burnham cast-iron BaseRay baseboard fed by 3/4 " copper--as opposed to the rest of the system's huge pipes. (The installer told me that the system was very likely originally steam, thus the huge pipes.)

Those 2 room never got very warm, with the baseboard typically being 15-20 degrees cooler than the rest of the system, but they did get warm. The new circ would not feed them at all, , with the feed pipe getting warm only to a point about 15 feet from the boiler, so they added a higher out-put circ with 3 power levels to choose from. Those heating elements now get as hot as the rest of the system on the middle circ speed--although the 2nd floor bathroom takes a little longer to reach full temp. It makes a little bit of a whining sound that can be heard on the 1st floor, but all in all, it is quieter than the old system.

The entire system gets hotter than the old one--with the old one never getting above 160 degrees. But, again, it was not the heating season when it was installed..... It also comes up faster from cold start.

The installer indicated that the next size down would have been fine, but if anyone wanted to expand the house, it might have been an issue. It will easily handle domestic hot water being added if anyone wants to do that in the future.

U.S. Boiler Company is a leading manufacturer of home heating equipment, water boilers, steam boilers, hot water heaters, radiators and boiler control systems.

Burnham Electronic Ignition Model W/NG. 164,000 BTU.

Good luck.

KoT
 
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Old 09-22-12, 06:40 AM
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I am also thinking to keep it old school. WM still makes all the eg and they told me they have not changed. As well even as they drop down in BYU they kept the same connectivity, taps so I could do a shoe in with no repipe.where are you, what was your design temp?. I am in Mn and I read it us about -14f here. Also I wonder if on my 250/00 BYU eg 65 if I could lower the water temp with cutout adjustment so I could open my rads to increas flow without roasting. I guess you'll know this winter how you did sizing what did your cycle times look like with the eg65. My only issue with buying another eg is they coas double the cg am dedicated he model.
 
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Old 09-23-12, 06:45 AM
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I too was a WM guy, but my installer--a top-rated by Angies List vendor that I had a super experience with-- talked me out of it. Said he had installed WMs for years, but that they had made a design change in recent years re: the method of connecting the boiler sections to each other that led to a higher chance of failing and leaking in the out-years. I have no idea if there is anything to it, and he did indicate that he would install the WM if I preferred it, but that Burnham was now his preferred choice. So I went with it.

KoT
 
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Old 09-24-12, 08:58 PM
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When I asked them about changes I was focused on connections. Maybe I'll talk to them again. How involved was the repipe, much cost there?
 
  #34  
Old 09-24-12, 09:08 PM
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By the way I asked them about downsizing. He said multiplying sqft by 75 would be reasonable for my age of home so 250000 in 200000 out was not oversized. That certainly goes against what I have been readingt what I have been reading.
 
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Old 09-25-12, 04:31 PM
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He said multiplying sqft by 75 would be reasonable for my age of home so 250000 in 200000 out was not oversized.
Yeah, SEVENTY FIVE BTU per Sq Ft maybe... with an exterior wall missing!

Total Horse Hockey.

Spend the time and money on insulation and air leak sealing, reduce the energy footprint of the home FIRST, and THEN put in a proper sized boiler.

"Insulation is fuel you pay for ONCE!" not every winter... forever.
 
  #36  
Old 10-30-14, 08:07 AM
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So newindustar, what size boiler you eventually installed? I have a 1920's house in Minneapolis about 2400 sf with two levels, not including basement. The basement is about 1200 sf, and currently heated. I had four contractors evaluated it, and I got from 120k to 250k BTU input with about 82% ~ 84% efficiency. I am leaning towards the 120K or a bit higher after I ran through several online calculators, and the Slant/Fin one. Still it is better to compare with a similar house in the same area.
 
  #37  
Old 10-30-14, 09:02 AM
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Lin - This thread is just over 2 years old and the original poster hasn't been back here since then.
Perhaps your question would be better off as a new topic.
 
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Old 10-30-14, 01:40 PM
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Yes please start a new thread...

Thanks....
 
 

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