Boiler Replacement Advice

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  #1  
Old 07-05-09, 09:20 PM
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Boiler Replacement Advice

I think I am in a similar situation to t_fin so I am posting this in hopes of also getting some valuable input.

I need to replace the original 1950 American-Standard gas boiler (Series 20B-J23, 240,000 BTU) in my 2700sf house with hot water radiators. We currently have two zones but are considering adding a third when we convert the attic into a master bedroom and bath (which would make the house 3300sf). We plan to be in this house for at least 12 years.

I have three estimates that seem to be quite different and I'm not sure how to compare them. I'll list them here from least to most detailed in terms of work to be done.

#1: $6,541 (this is the local gas utility, National Grid)
Burnham 206 HNC, fan-in-can
"customer responsible to have boiler removed asbestos insulation inside jacket"
[yes, that's the complete estimate]


#2: $14,635
Buderos, G/B 142/45 95% AFUE
Isolation valves to to feed and return piping system
Copper type (M) pipe and fittings for heating
Copper type (L) pipe and fittings for domestic
Watts combination boiler feeder back flow prevention unit
Grundfos multi-speed circulator pumps
Watts flow check valves
Extoll No. 30 expansion tank
PVC exhaust plumbed to exterior of house
TACO electrical control panel
Electrical wiring
Exterior temperature sensor
Buderos 32 gallon domestic hot water heater plumbed to existing domestic water piping system
CO 2 detector hard wired
Disassemble/dispoasal of existing heating system and domestic hot water heater


#3: $13,480
Lochinvar KBN105 95K BTU 94%, wall mount with outdoor reset and domestic water control
2 Taco 00R-IFC 3-speed circulator pump with check valve
1 Superstor SSU-45 stainless steel indirect hot water tank (or SSU-60 for additional $800)
Installation of listed equipment
Reconfigure piping within existing mechanical area for supply and return manifold
Connect to existing radiation in basement
Removal of existing venting system and cap chimney
Installation of piping from new boiler manifold to existing distribution piping
Installation of new expansion tank
Installation of new Spiro vent air eliminator
Installation of isolation valves
Installation of PVC flue (direct vented at front location of home) and CO detectors
Installation of PVC flue vent for sealed combustion
Condensate for boiler shall pump to sink in basement
2-year warranty on installed parts and labor including 1 tune-up after 1st full year
Removal and disposal of existing boiler (professional asbestos removal company must be contracted to remove any existing asbestos)


#3 looked at every room in the house and took the plans back to his office before supplying an estimate while #2 never left the basement.


So here are my questions:
Why is #2 specifying a 32-gallon and #3 a 45-gallon hot water tank and will that be enough for a family of 4 in which we might do a load of laundry and run the dishwasher and then take four consecutive showers or should we have a 60-gallon?

Why did #3 measure where the exhaust flue could go on the exterior of the house (and determine that there wasn't enough room on the side of the house between the chimney and the gas meter to meet code so the two exhaust pipes will need to come out the front of the house at least 48" from the ground) while #2 didn't measure and didn't mention any possible issue?

Why did #3 warn me away from aluminum boilers like the Buderos while #2 said there was no reason for concern?

Why did #2 specify copper piping and fittings but #3 didn't?

Why does #3 mention where the condensate is going but #2 doesn't?

Why isn't #2 mentioning asbestos removal?

Are these costs reasonable?

I would be grateful for any help in making this decision.
 
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  #2  
Old 07-06-09, 09:29 AM
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That's a lot of questions, but here's a couple more.

Which one did a heat loss?

What's your outdoor design temperature? How is the building envelope for insulation and air sealing?

Which one asked about your domestic hot water consumption?

#2 wants to install a honking big boiler. The 142/45 is 161k BTU/hr input. You could heat 3-4 houses and 60-80 gallons of domestic with that. Because it's so big, it only modulates down to 43k BTU/hr, which is probably at or above your design temperature heat loss. So it will short cycle on its bottom end modulation except for hot water calls. And it won't need all that output to meet your needs. You could probably use a 142/24. Even with a mod/con boiler, it is still possible to oversize and end up with a poor-performing (and expensive) system. The 32 gallon indirect is not well-matched to the oversized boiler, either. Jet engine on a canary....

#3's boiler is more in line, size-wise. But you might not need the 105. Probably an 80.

On the disparity between thoroughness of site visit and comments by #2 and #3, it depends. Some guys factor all that stuff into their head and it comes out right. Some guys walk you through it all, and take advantage of their time on site to have a very good handle on the job.

Same with the estimates. Some guys are very thorough and list out make/model of every last thing. Some guys give you the basics, but when they do the job, all the components and the quality of work is right up there with the best of them.

On the whole, as a first impression I like #3's specs better than #2. But I don't think you need a 105 unless you go with the 60 gallon indirect. And when it comes to sizing, I would alter my lifestyle ever so slightly (like not doing 4 consecutive showers while running the dishwasher) to avoid going up a boiler size. Two-thirds of your boiler's time will be spent heating the house. One-third on making hot water. Family of four should do fine with a 40-45 gallon indirect.

You do need to be very clear about what is included (or not) regarding the asbestos abatement and disposal.

Also ask #3 about how he will treat the condensate that goes into your sink. If you have cast iron waste pipes or septic, it will eat through it in very short order if untreated. Condensate has a pH of about 4, i.e., it's an acid. Neutralizers are simple and easy; basically passing the condensate through a tube or bucket of lime chips before going down the drain.

The jury is still out, IMHO, on the aluminum block boilers. With proper care and maintenance, and attention to water chemistry, they are probably fine. But they haven't been around here that long and it is for sure that they are more sensitive to water chemistry than some other materials.

It is excellent that you are keeping the hot water radiators. They are truly awesome with a modulating boiler running outdoor reset. Consider trying to find some salvage radiators when you do the addition.

As for #1, toss that one in the recycle bin.
 
  #3  
Old 07-06-09, 07:51 PM
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Thanks very much.

#3 may have done a heat loss because he had previously given me an estimate for central A/C for which he took the plans. I will ask him.
#3 asked about domestic hot water consumption - how long our showers are usually, how many loads of laundry we do, etc.

I found this online calculator:

Home Heat Loss Calculator

I used an outdoor design temp of 0 degrees for Boston
I know my house has R-20 blown fiberglas in all the ceilings
The walls are surprisingly well insulated but I'm not sure how well so I estimated R-10.

I came out with a little over 60,000 for the design heat loss
 
  #4  
Old 07-07-09, 11:35 AM
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Correction, I got 146,000 after fixing the inputs (wrong whole house volume, reduced wall R, and added basement walls).
 
  #5  
Old 07-07-09, 12:26 PM
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Originally Posted by 1950original View Post

Why isn't #2 mentioning asbestos removal?
.
Was #2 a local guy or a bigger company? the bigger company that gave me my estimate told me an extra 500 on top to remove the boiler 'correctly'. The local guy just said he would remove the boiler and no mention of asbestos. I hired my local guy because the big oil companies just measured my baseboards but my guess is they care more about following disposal regs than my one man operation that I hired.
 
  #6  
Old 07-07-09, 02:33 PM
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The ASHRAE outside design temp for Boston is 9 degrees not 0 degrees. So the heat loss is off already.
 
  #7  
Old 07-07-09, 06:51 PM
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R-20 in a ceiling isn't very much. Better add some more.
 
  #8  
Old 07-08-09, 02:18 AM
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I am impressed with the quality of good advice here.

I agree that the 40 gal heater would be fine. The advantage of a bigger tank is that it allows an efficient boiler to rest more. A small hot water tank is always waking the boiler up. While a bigger tank costs more it does eventually pay back. This is a case where over sizing is not bad in the long run. The new tanks are well insulated and you can add more to that.

While the advice in the top sticky post on over sizing boilers is very good, there are exceptions. Because you size for the coldest day of the year, you are oversized all the rest of the time, so the better heating systems address that problem in different ways. High AFUE is not one of those. That is a different question.
To illustrate, we set up an efficient boiler to heat domestic water only, no heat. That boiler which could heat the whole building, used only 10 gal of oil per month for a family of four. To find out how much of that was standby loss, we disconnected it from the domestic HW and let the boiler heat only the tank. For 1 year we used 2 gal per month just to keep the tank hot. That was a good quality electric style tank with no added insulation connected to a side arm exchanger. I would like to try it again with an indirect tank to see just how close that would be.

In addition to those dealers named, I would see if you have dealers of other high effeciency systems, eg: Viessmann, Energy Kinetics, Burnham, etc.
 
  #9  
Old 07-08-09, 06:12 AM
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Originally Posted by buzz_mn_58 View Post
R-20 in a ceiling isn't very much. Better add some more.
my energy auditor said i had r19 already and advised another r11 on top of that. So i think the standard is to shoot for 30
 
  #10  
Old 07-08-09, 06:22 AM
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Bilbo, I have concerns about oversizing the tanks. I totally agree the larger tank will wake up the boiler more (I like that analogy) but it also keeps it awake longer. Although not a bad thing to run longer but if you are not short cycling the boiler with the smaller tank why not use the smaller tank. I feel heating more water than needed is a waste of money. The standby losses of indirects are low it still has standby loss. The larger tanks tanks longer to recover. You can actually have more usable hot water with a smaller tank than a larger tank. I believe the recovery time is the loss here.
For example:
Let's say you have the two following tanks.
Tank 1.
30 Gallon, boiler DOE required is 99k and a flow rate of 6 gpm.
Tank 2.
70 Gallon, boiler DOE required is 150k and a flow rate of 10 gpm
The boiler is rated at a DOE of 80k
To achieve the proper recovery you need the proper flow rate in the tanks.
If you look at the boiler size and flow rate of the tanks the flow of tank two will be too fast to even get a 20 delta through the boiler, so cooler water will go to the indirect tank coil thus increasing the recovery time as compared to what it would be with the proper flow rate and boiler size.
On the other hand if you match the flow to the boiler and not the coil in the indirect, the recovery time is again increased due to less flow. Remember less flow less heat transfer, increased flow increased heat transfer.
 
  #11  
Old 07-08-09, 08:27 AM
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Hi 1950,
As an energy auditor, my take on your upgrades is a bit different, but you asked.

Converting attics to living space is a whole topic in itself. It can cap off your existing structure or end up being a hot or cold space that everyone tries to avoid. When you are ready, but remember, it will need proper access and egress.

"I need to replace the original 1950 American-Standard gas boiler (Series 20B-J23, 240,000 BTU"
It would be hard to defend the old beast, so your decision to replace is good, however, there are a couple of steps I like to see before you jump. Resize your house before you size your boiler. Not necessarily the physical size, although that needs to be considered as you mentioned, but its heat load. If the heat requirements for your home can be cut in half, then your new and much improved boiler can be cut more than half. The improvement will save on the new boiler cost, reduce your yearly energy costs, improve the comfort of your home and impress prospective buyers when you are ready to sell. In 12 years they will most likely REQUIRE an energy rating and related improvements when a home sells, so starting now will mean the things that need to be done first won't be buried under that previous improvement.

The absolute best way to start is with an energy audit. The report will outline where and how to make your improvements. It's a step that many want to skip, but air leakage and selection of improvements are best done in the proper sequence. A good audit will more than save its cost. The blower door test and Infrared scan are worth the extra.

From your original post:
Design outdoor temp: 0
Heating degree days: 6250
Ceilings: 1211sf at R-20
Walls: 3414sf at R-3.4
Windows: 304sf at R-1.8
Slab on Grade: 159ft perimeter at R-0.47 (you corrected this to a basement)
Infiltration: 28,408cu ft at 1.0 air change/hour
Internal heat gain: 4 occupants


As for you boiler quotes, save them, and see what they look like after you weatherize.

Bud
 
  #12  
Old 07-09-09, 03:16 AM
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rbeck, you are correct.
My thinking is always prejudiced by my having been a dealer of low mass, cold start boilers which beat the heavy ones only if they are set up to maximize the off time periods. Many of my assumptions do not account for the mass of the boiler and how it is set up.
 
  #13  
Old 07-09-09, 04:33 AM
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Originally Posted by Bilbo View Post
To find out how much of that was standby loss, we disconnected it from the domestic HW and let the boiler heat only the tank. For 1 year we used 2 gal per month just to keep the tank hot. That was a good quality electric style tank with no added insulation connected to a side arm exchanger. I would like to try it again with an indirect tank to see just how close that would be.
Thread drift warning. Sorry, can't help it.

This is a very cool experiment. Neat stuff, Bilbo. It works out to about 278k BTU/month input. Figure 80% efficiency and that's 222k BTU/month that goes into heating the water. Or about 3700 BTU/day. Assume a 40 gallon heater (what size was it?), and that's 333 pounds of water to keep hot. 3700 / 333 = 11 degrees per day. Or about 1/2 degree per hour standby loss. IIRC, that's about what a good indirect is rated.

OK, back to the thread. There is very good advice here on looking at the envelope after improvements to figure the heat load. The domestic water load will most likely be the larger of the two, and I agree with rbeck that if you can size the indirect to the smallest that can meet a continuous draw need (or thereabouts), that would be a preferable way to go.
 
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