Hi all.. seems to be some good info on this forum.

I have an old hot water radiand system. Boiler is a Crane 14 changed over to natural gas. The gas burner has a rating of 200k btu max /65k btu min. The piping is cast or steel with the radiators hung on the wall. The system makes one large loop araound the perimeter of the house. 1 and half inch supply pipe. The house is one story 1575 square feet with a small basement about 800 s.f. The rest is inclosed crawl accessed from basement. The system is slow to heat but once it gets warm it stays warm. The wife dont want to go with a heat pump (likes this kind of heat).
I want to replace the boiler with a newer and more efficient boiler and keep; the pipe system intact. I would like to get one of the efficient models with the tax credits.
My questions are: will one of the new boilers work in my application ?
what size (btu) boiler do I need for my house?
is one brand boiler better than the others?
.will a newer boiler with the smaller heat tank even work in my system?
I usually run my hjot water at 180 degrees, will the new boilers supply that kind of heat?
anything else you guys think are important factors on getting a new boiler installed?

 

Your first step is to perform (have performed) a heat loss calculation for the house. Don't just replace the boiler with one of the same size. The existing boiler is likely oversized.

Nobody can tell you what size boiler you need without a calculation.

 

I have used the heat loss calculator from slant fin and came up with a heat loss of 46kbtu which seems kind of low to me. i also used a heat loss calculator last year that i obtained from wiel mcclain website and it came out to 71k btu heat loss which seems more in line to me.
I also did a quick calculation of how many btu the current boiuler was using by counting the number of times the gas supply meter dial turned and came up; with 150k btu goig in.

 

i have oil, and dont know anything about gas, but i just have to ask...dont you burn yourself on the 180 water? The reason i ask is i used to have a convention boiler and i did have to jack up the water in winter to make the baseboards warm enough. so i had to watch not to burn myself with the water. it's a terrible system.

i replaced my old boiler (with a long thread in this forum plus pictures if you are interested) with a low mass one and indirect hot water. I also did an outdoor reset. If you arent familiar with outdoor reset, search on this forum. It's amazing. i went from 1200 plus gallons in a year to about 900 the year after i installed everything. The outdoor reset is fantastic as on 'warm' days in the 50s, the water only heats to maybe 130 or so. But even on the coldest days, i dont think i've seen it go over 170. I think the reason is the great circulation. i have a MUCH more even and steady heat than with the short cycling of my old unit. I also only have one zone and i hate it but what can you do without spending $$$$.

also with the separate indirect hot water heater, i picked a nice cool temp (not that 180 i used to have in winter) of about 120 for domestic and saved myself a bunch of money because i was heating up hot water to 180 all winter needlessly. Of course i turned the boiler down to 120 in summer to save oil and keep from burning myself. But even at that i was burning needless oil because the few gallons in the coil would get cold and the boiler would fire up way too often.

hopefully these same theories and technologies can be used for gas, but the experts should chime in with that info.


edit: just read ur post again and see you have radiators so that does change things a bit. thats not a low mass thing

 

150,000 Btu/hr seems enormous for the size of your house. If the boiler is properly sized, it should fire continuously - or cycle very little - during the most severe winter weather.

How old is the house? Describe insulation, windows, etc.

The SlantFin program, with proper input data, should give realistic numbers. Check all the data.

My house, built in 1951, is well over twice the size of yours - yet my boiler is significantly smaller. Location: northern Illinois.

 

I know that 150k btu is too high. I figure 71k heat loss = net I-B-R of at least 71k on a new boiler.
The houise was buile around 1938-40. I put in all new double pane windows last year.
The wall insulation seems to be rockwool from what I have seen. The attic had apx 6 in of rockwool and last year I put r30 attic blanket over the top of that. Has newer doors and new storm doors. The basement, crawl , and system piping has no insulation.
im wanting a new high efficient boiler like a ultra or alpine and am wondering how one of these units will work in my application. I dont want to change any piping or radiators.
Are the new units made to run with 180 degree water temps? Will they be able to keep the radiators hot like my current unit?
Can I just use water or do i need to change to antifreeze?


On a side note : I had a local company come out and give me an estimate. They gave an estimate for a new 200k btu boiler based on the fact that was the max rating on the boiler that I currently have.

 

The normal approach now is to go with the DOE Btu/hr rating (not I=B=R) -- match that to the estimated heat loss without adding additional margin.

Slapping in the same size (or larger) boiler is typical for contractors - who won't (or don't know how to) perform a heat loss computation. But, in a way, you can't blame them - homeowners would expect that to be done for free, possibly by multiple bidders.

From what you describe, I tend to think 71K "sounds" somewhat reasonable (but you need to take responsibility for your own heat-loss calc). Your insulation seems comparable to my 1951 house. But you might want to staple up insulation above the crawlspace - to insulate the floor above. Depending upon the amount of space between the bottom of the crawlspace and the floor above, that can be a misrable job. I wouldn't worry to much about insulating the basement walls unless there's more that a couple of feet above grade, exposed to weather. (I assume the basement isn't finished?)

If you really want to run the water at 180 deg (possibly because of limited radiation?), you might as well forget a super-efficient condensing boiler. At that temp, there won't be any condensing - might as well install a conventional boiler, which is simpler and requires less maintenance.

And if you do intend to install a condensing boiler, you'll need a different, outside exhaust or a new chimney liner.

 

If you installed a boiler of 80% or higher, you will need to have a stainless steel lined chimney if you don't already have one.

It's also important to figure out how much radiation you have in your house. The heat loss will give you the boiler size, the amount of radiation will tell you the maximum water temperature you will need to heat the house at design temperature. The new boilers will heat water to 180 degrees just fine, but you don't need to and you shouldn't if you want to save the maximum amount of money. The idea behind modern systems is to run the boiler as long as possible. That is the most efficient and the most comfortable way to heat.

 

Redo the heat loss. What part of the country are you in?

1575 sf, and guessing heat loss per sq ft for that vintage of construction with upgrades you describe is around 47k BTU/hr. Add basement and maybe around 50-54k BTU/hr.

You are describing a monoflow-tee (aka diverter-tee) system with cast iron radiators. That's a good candidate for a modulating/condensing boiler with outdoor reset. No problem keeping that piping system with a new boiler.

The approach with these boilers, as someone else mentioned, is to keep the water circulating almost constantly, but using a much lower than 180F temp for all but the coldest couple days a year (and maybe not even then) by an outdoor reset control that seeks to match the heat input to the heat loss. The boiler responds by lowering or raising its input rate. Like cruise control in your car. Even and steady. The house will be very comfortable.

Keep shopping installers. The installer makes or breaks the performance of your new system.

There are also good tax credits for any further weatherization you can do, which is the cheapest, most effective way to save on energy costs. Especially if it means you can downsize the boiler -- less initial cost to install, less fuel to heat the house. Often state and utility rebates available, too. See dsireusa.org for a listing for your area/utilities.

 

[QUOTE=drooplug;1775317]If you installed a boiler of 80% or higher, you will need to have a stainless steel lined chimney if you don't already have one./QUOTE]

It's relevant to understand that all such codes that are published by industrial/professional organizations have no authority unless implemented by local jurisdictions, e.g., cities. Otherwise, following them is optional - guidence only. They may be good ideas or, possibly, overkill in some situations. Or, some few code requirements may be put forward for competitive reasons (some have been invalidated under anti-trust laws).

Installing a stainless steel chimney liner at 80% boiler efficiency, if not mandated by local ordinances, should depend a bit upon the construction and condition of the existing flue.

I'm most familiar with the National Electric Code (published by the National Fire Protection Association). The thing is, there is no such thing as a National building code, at least in the U.S., unless adopted by the federal government - which I'm unsure whether the feds, under the U.S. Constitution, can do. In many locations in the U.S., including mine, there are no building codes. If there were National building codes, who would enforce them? The FBI? Wouldn't Congress have to approve them?

I try, on this forum, to recommend what I personally think is proper, reasonable, and safe. If what I suggest is trumped by local ordinances, so be it: that should get flushed out when the contractor or owner pulls local permits (assuming any such permits are required).

 

I think what Doorplug was trying to get across is that if you go with a high-efficiency condensing boiler, the chimney (stack) needs to be of a material that won't corrode out. Galvanized pipe will quickly get eaten up by the corrosive elements in the condensate, but a non-condensing boiler would run just fin with a galvanized pipe. So, if you plan to upgrade, you may have to facor in a new stack into your equasion. You can always run the venting in a different way too. You could go out the side of the house which would be shorter. If you vent PVC, there is concern about Chlorides in the condensate coming back to the burner and pitting it and reducing burner/HX life. The best is stainless AL29-4C.

Gruni14

 

OK, makes sense. Some old brick chimneys had no linings at all.

My boiler flue liner is vitrified bell tiles, with bells up. The tile was completely bedded in morter as the brickwork went up. My natural gas boiler efficiency has been tested at 79%. The chimney and tile liner are 60 years old - the chimney has been tuckpointed, and the liner recently inspected (reported to be in good condition).

I've "heard" that when and if I replace my boiler with another conventional, non-condensing unit with 80+% efficiency, the "codes" would require that I install a steel liner. I haven't actually seen such code, but I might choose not to follow it. (There are no building codes in my fair city.)

I don't encourage anybody to not comply with codes, even if they haven't been adopted by the political jurisdiction, unless they feel confident in being able to evaluate and accept the risks.

P.S. Here is info from Weil-McLain for installation of one of their current, gas-fired, non-condensing boilers:

"A lined chimney is preferred and must be used when required by local,
state, provincial and national codes, laws, regulations and ordinances.
Vitreous tile linings with joints that prevent retention of moisture and
linings made of noncorrosive materials are best. Advice for flue connections
and chimney linings can be obtained from local gas utility. Type B
double-wall metal vent pipe or single-wall vent pipe may be used as a
liner."
Source: http://www.weil-mclain.com/en/multim...ler_manual.pdf

 

ok I redid the slantfin heat loss calc. I came out to 66k. including the heated basement and crawl. My mistake there was I used 0 degree outside temps instead of the -10 that is called for in my area. I was under the impression that the boiler sizing should be done using the net i-b-r but now I guess its the Doe cap.
I would really be interested in figuring out my capacities of my radiators now if anyone can point me in the right direction. I recall doing some figuring a year ago that involved countuing the rows and columns but I cant seem to find it now. That would help me determine if my system is good enough for a high eff. boiler?
I have had about 5 estimates ranging from 5100 to 10 grand just for the boiler. The ones I am looking at are : 5100 for burnham alp105 installed 8500 for alp105 installed
and 9600 for wmclain ultra 105 installed.
Do these prices seem in line with what you guys have seem?
Why the big diff for the 2 quotes on the burnham?
All the estimaters seem to come to the same conclusion on what size boiler I need.
The one estimater I liked (8500) actually looked at my radiator sizes and asked some questions the others didnt. He said I should run my hot water @ 140-160 degree range.
They all recommended pvc exhaust and intake going through the wall and eliminate the chimney. They all said there would be no problems with condensate or chloride. What have you guys experienced?
Thanks for all the info you guys have provided. It really helped me ask some good questions of the installers.
When i asked the guy why his 8500 estimate was so much higher than the other guys . he stated there was no way he could install the boiler for 5100 and didnt see how the other guy could do that. He said to make sure they were NATE certified or I might regret using that company for the install.

 

I'm looking right now at the 2009 ASHRAE Handbook. There is no location in Indiana with a 99% heating drybulb of -10 deg F - or even lower than zero. (ASHRAE recommends using the 99% temperature for heat loss calcs and design.)

Here are some examples:

Evansville +12.1 deg F
Fort Wayne +3.8
Indianapolis +6.4
South Bend +4.5
Terre Haute +6.6
Lafayette +4.2

Using -10F will throw your heat-loss results much too high - on top of the margin built into the Slant/Fin program.

Keep in mind, the 99% heating temp isn't the same as the expected annual low or the record low. But the "Manual J" programs, like Slant/Fin, are based on the 99% heating temp.

As to different contractors and their prices: I recommend that you personally check references before considering a contractor, preferably before asking for a price. I think if they knew you were talking to six different contractors, their interest might drop off a bit - probably the better ones might drop out.

There can be incidentals you need to know whether they have included or not. For example: circulator, balancing or zone valves, expansion tank, flo-control valve(s), shut-off valves for circulator maintenance, new pressure control (make-up) valve, initial air bleeding of the system, warranty, outdoor reset, all controls, and others that I've forgotten. A good, highly recommended contractor may include such items - while a low-baller might not.

If you don't need to replace your existing boiler right away, you might consider waiting until spring - to give you more time to ponder things and possibly avoid problems with a new install as winter sets in.

 

I used the design outdoor temp. as stated on hvac toolbox website.
US Design Outdoor Temperature and Relative Humidity - Winter and Summer

January dry bulb temp for Indianapolis was stated as -10. Most of the estimaters said it was 0 degree.
Now Im confused. Is there a ashrae website that i can look at it?

I could just replace the gas valve on the old boiler and prob. get another year out of it.
I just figured with the tax rebates that now would be the best time to replace the old boiler.
Thats why Im here : trying to get all the help and info I can so I can make a good decision.
At first I figured i would jsut do it myself and probably would with standard boiler but these new ones seem a lot more complicated and expensive.

 

I have no idea where your site came up with the temperature info. The data that I quoted is from the 2009 ASHRAE Handbook, Fundamentals. Those professional/code organizations like to sell their literature, so they don't put it on the web. If you have a fax number, I can send you the data for Indiana.

What's wrong with your gas valve? If you buy a new boiler, it won't come with a new gas valve. Might as well replace it now?

 

FWIW, my ragged old ASHRAE book says Indy is +2F.

Radiator output is done by Equivalent Direct Radiation (EDR). Output is around 150 BTU/hr per square foot of EDR. A decent guide to ballparking EDR is Radiator Sizing Guide

or look around for a copy of "Every Darn Radiator", which lists many, many.

In terms of cost, you often get what you pay for. FWIW, no quality installer in my part of the NE US would even think about a full modcon install for 5k. Couldn't do it. Check references, ask to see pictures of installs, etc.

 

If the original poster is referring to the electrically operated gas valve controlling the burner a new boiler most certainly WILL have a new gas valve. On the other hand, just because the gas valve on the burner is defective does NOT mean that a whole new boiler is the most cost-effective method of repair.

 

The 2009 ASHRAE Handbook (Fundamentals) shows these Indianapolis (airport) heating drybulbs:

+6.4 deg F (@99%)
-0.5 deg F (@99.6%)

 

Thanks - I stand corrected. I wasn't thinking correctly.

 

ok so I re-ran all the numbers I could and here is what i came up with:

House is 1575 sq ft. plus basement 575 sq ft, and heated crawl about 1000 sq ft.
double p;ane windows, insulated steel and storm doors , insulated 3 1/2 in sidewalls and arount r-35 to 40 in the ceiling

the supply p;iping on the single loop diverter tee system is 1 1/4 in


Slant fin heat loss:

53k btu @ -10 F
46k btu @ 0 F
40k btu @ 10 F
33k btu @ 20 F
26k btu @30 F design dry bulb in my area is 2 - 4.6 degree F ( thanks guys )

As close as i can figure the total sq ft EDR for all radiators is 250.62.
All the piping (apx 160 ft x 1 1/4 in) is exposed and not insulated. It is radiating heat into the basement and crawl and I suppose eventually rises up into the rest of the house. I dont know how to figure EDR on the piping of if I even should.

So , with the updated infor do you guys still think a mon/con boiler will work here?

Total radiation out of the radiators with water running @ 140 F would be 22.5k btu\
@ 160 F would be 32.5k btu

What size boiler would I need? Maybe Alpine 80?

As close as I can figure I have about 50 gallons of water in the pipes and radiators. Will a new condensing boiler heat that much water?

Also how do you figure how fast or slow to run the circulator? and does it make a difference? Are they adjustable?
And how do you figure your return temps? I have seen mention of a 20 F temp drop between the supply and return. What difference does it make? what is the return has a 10 degree or a 30 degree temp drop? how much diff does it make and how to adjust for the difference?

Thanks for all your input.

 

Ok. So 250 * 150 = 37.5k BTU/hr output at 180F. If your house heats adequately at design conditions, then you now know that your actual heat loss is less than 37.5k at design. You also know that there is no point in having a boiler much larger than around 50k, because your max radiation output is 37.5k (plus a little for the big piping).

Taking on the first part, the actual heat loss at design is

 

Please stop telling this guy to perform an EDR calc on his radiators.
It doesn't matter in a hot water system where water temperatures and cycle times vary. That's for sizing square footage of steam production.

And the design temperature of any place on earth changes every year so take all that with a grain of salt. A new number is just as vague as an old number since neither may be an accurate representation of the future.

FWIW, I recommend a mod-con like Triangle Tube or similar and a good piping strategy.
Twin mod-con Triangle Tube installaton | Flickr - Photo Sharing!

 

'That guy' already did an EDR calc. Note that it's not being used in a strict design sense. It's a point of reference and viewed in combination with other data. EDR is a standard measure of output for radiators, both hot water and steam. I agree completely that EDR matters less in hot water applications than steam. But it is useful to know the radiator output, just as it is useful to know the output of, say, fin-tube baseboard when evaluating heat output at various water temperatures.

That's a really, really nice TT install.

 

How is it useless? I used it in my house to determine my maximum and minimum water temperature for my boiler? Why should I run it all the way up to 180 when I only need 142 on the coldest day?

 

Pretty.... It's the big brother of my install (currently in progress...) What's the green box under the Tekmar? And what are the little boxes under that?