I will try to keep this somewhat concise despite my mass confusion. Here is my situation: 1916 two-story wood frame house, 2400 sf, 3++ bedrooms, 360 sf of single pane windows with storms, 63 sf of doors, walls insulated to R12, attic insulation is 50% R12 and 50% R48. One Burnham Series 2, 130 MBH boiler, 80% AFUE chugging in the basement on a single zone. Original cast iron rads in all rooms with all the original cast pipe serving them.

Dilemma one: I have run a couple of different heat loss calcs and each one comes in at about 54,000. I know I should have expected the boiler to be oversized, but by a factor of over 2.5? Question #1, given what I stated above, does 54,000 sound reasonable, or did a screw up a calc? Question #2, given the significant amount of cast iron on the system, is it possible the boiler wasn't oversized, but sized to account for the massive piping and such?

Dilemma two: Boiler Recommendations? Been researching the high eff units approved for the tax credit and have boiled (no pun intended) it down to Burnham, Triangle, or Lochinvar. Burnham, as that is what I have and has been maintenance free, Triangle and Lochinvar because I have seen some encouraging comments on them. Is there another? Munchkin, maybe? Sadly, and reviews i see on any boiler are always negative (what ever happened to "if you don't have somehting positive to say??") Does Triangle make a floor model, I thought I saw one in my searches, but now only find the wall-mount.

Dilemma three: Indirect hot water. How much more capacity should I add to the boiler to cover the indirect system? Currently my gas-fired 50 gallon tank keeps up with all our needs. How are the indirect systems sized? I see some with minimal tanks, others with 50 gallon.

Appreciate any input you guys (and gals) can provide. Want to get this one in before the cold season hits.

Thanks!

ps...I know single zone BAD, nothing I can do about that without starting all over again.

 

2400 sq ft isn't a large area. Why are you replacing the existing boiler, and what problem are you trying to solve? Has the single zone worked in the past? Properly balanced, it should be OK.

The iron pipe and radiators are not a problem - actually an advantage, in my opinion. What leads you to believe they are a problem?
Doug

 

My main concern is if my calc seems reasonable. I don't have a problem with the cast iron at all, I was wondering though if the amount of it would affect the heat loss calc. Given the significant difference between my calc and the existing boiler size.

I'm considering replacing for two reasons: increased efficiency and to take advantage of 2500 in rebates and incentives.

The single zone is not a problem. I only mentioned it becuase others may see it as one.

So any input on my questions?

Thanks

 

Just a quick observation on the heat loss calc, it seems low. A 1916 house would have board sheathing and no insulation. Now, if they plastered inside the stud bays it might be reasonably well sealed, if not, the board sheathing leaks air like mad. What insulation was installed, fiberglass or cellulose? And what type is in the attic? Also, do you have a basement and what has been done to insulate down there?

It's not unheard of to have a heat loss at that level, it just requires some really good insulation, windows, and air sealing.

Share some more information and I'll see what comes up.

Bud

 

Bud,

The old place is actually fairly well insulated with cellulose in the wall cavities and attic floor. I have added a layer of fiberglass to the accessible areas of the attic to get them up to the levels I mention below. Amazing it isn't a drafty place. A previous owner went crazy with sealant and securing clapboards. Under sheathing is tongue and groove boards.

Full basement with insulation in all the joist/sill pockets.

Hope this helps

 

That's what I wanted to hear. Sounds like you are ok.

Bud

 

So the original boiler was simply very oversized? No need to worry about the "oversized" iron piping feeding everything?

Any thoughts on boiler choice? It seems to me to be a pot shot in picking one, as I can't find much on reviews.

 

Dilemma 1: 54000 / 2400 = 22.5 BTU/hr/sf. That's the heat loss in BTUs per hour per square foot. Your numbers sound about right. Big old Victorians are ~40. 1970s-80s construction 20-25. Your older house with some air sealing and insulation upgrades is right in there. It probably used to be 30+.

Dilemma 2: I used to have a Series 2. Rock solid, but about 3-4 times bigger than the house needed. Now I have a Burnham Revolution, installed a few years ago. Rock solid. If the Revolution tanked tomorrow, it would be replaced with a Triangle Tube Solo 60. This is the boiler I would suggest for you, assuming you don't have an outrageously high domestic hot water demand (like a whirlpool tub, giant car wash showerheads, lots of people showering at the same time, etc.).

Dilemma 3: You do not add to the boiler output to account for the indirect. Typical boiler system control (particularly with the modcons you're considering) has 'DHW priority' which turns off the space heating for a few minutes to devote the full output of the boiler to satisfying the indirect demand. Very nice. You could do a 40 gallon indirect (the Triangle Tube indirects are good; also check out HTP SuperStor).

p.s.... single zone not bad. Single zone good. Keeps a good load on the boiler. Unless the current zoning leads to uneven heating or lack of control of heat in certain rooms, do nothing to change it. In fact, the outdoor reset control that is built in to the modcons you're considering is going to LOVE having a lot of cast iron mass. You will dial down the reset curve to meet the heat loss, the system will use supply water temperatures in the 75-120F range nearly 98% of the heating season, so it will condense like crazy and give you the full 95% efficiency. That rocks.

p.p.s... depending on how your system is piped, you could potentially add thermostatic radiator valves to selected radiators (e.g., in the bedrooms) to turn the heat up or down. But I'd run the system for a full heating season on the outdoor reset before doing that.

p.p.p.s... find a good installer. Installation is everything with these modcons.

 

Forget about the amount of radiation and piping as far as boiler sizing due to the fact the amount of radiation and water volume has absolutely nothing to do with heat loss. Heat loss is the amount of heat leaving the structure per hour.
It is not uncommon to be 100 - 300% over sized.
What is your hot water demand? How many full baths, any high water use tubs or showers?
As far as boilers they are all good boilers. It's a Ford/Chevy thing. Maybe not a good analogy anymore. How bout a Ford/Dodge thing.

 

To size the tank, look at the chart on various brands such as Triangle Tube Smart tank. 30 to 40 is plenty for most homes especially with dhw priority.

Edit: I just realized xiphias made this point already:

If you put an electronic control that has domestic hot water priority, that puts the house heat on hold for few minutes until the dhw is satisfied, instead of heating the house and water simultaneously. Therefore you size the boiler to the house and do not add the domestic hw load.

 

How about a Dodge vs Toyota/Honda thing!
It is not a matter of opinion but empirical fact that some brands of cars and boilers are more reliable and more efficient than others.

 

Thanks for all your help!

In terms of the Dodge/Toyota/Honda. Absolutely agree and like all buyers I want Honda quality for a Dodge price.

I'm looking closely at the Burnham Alpine 80 with IHW. Would I be going wrong? Been happy with my Burnham series 2. Is it even a Honda? Other considerations are listed below in my first post.

And where is this empirical stuff?? I have been searching all over trying to find anything on boilers and reliability and come up dry. Waht few sites I do find seem to be slanted to get you to favor one brand over all the others.

 

The type of pipe or heat emitters doesn't enter into the heat loss calculation.
Doug

 

The Alpine, the Knight, the Munchkin, and a few others use a stainless steel heat exchanger made in Italy by Giannoni. It's ok, not great. Triangle Tube's heat exchanger is their own design, and it's pretty cool. It also uses a slightly different - and probably better and more durable - stainless (439, compared to the 316 used by Giannoni).

Don't get me wrong, I'm a big Burnham fan. But if I needed a new boiler tomorrow, it would be the TT Solo 60.

 

Well folks, had my first contractor in for an estimate. Guess what, "yup with these sizes of pipe, ya gonna need a bigger boiler" His recommendation...100. Of course I protested, and he just blankly looked at me. think he was a bit surprised I had done my own heat loss calc, that I had pre-selected some equipment to discuss, and that I wanted a detailed estimate breaking out equipment costs. "why would you need that, for tax purposes?" Response, ""No, I know what I can buy these for elsewhere, I want to know if ou can match or beat the equipment price."

So...stand my ground on the smaller boiler? This guy has always been reputable before in my other dealings.

 

I suspect that there are hundreds, or maybe even thousands, of reputable installers that simply don't know the science behind what they do. Ask Xiphias about installers who understand the term "pumping away" for an eyeful.

Many installers learned their trade through an apprenticeship program or by learning from an older workman. Often when confronted by a new way of doing things they respond with, "Well, this is the way I learned and I've never had any complaints with my work." Their workmanship may be top notch and their pricing and accounting unquestionable but if they don't understand the "why" behind the work, if they haven't kept up on the improvements over the years you will get a second rate system.

Anyone that is unwilling to do a comprehensive heat loss calculation or who says he can install an efficient system by using outmoded "rules of thumb" needs to be thanked for their time and gently shown the way out.

 

Yes I suspect that if I had to show every installer not willing to do a heat loss the door, I run through all the installers real fast. This is Syracuse after all.

 

I decided that I wanted an installer that knows how to install and sold what I wanted. I put in a Prestige and had it piped for both direct and p/s. This cost more but I was happier with the options and was planning on doing radiant floors in the kitchen and some flkoor warming in the baths later and wanted options. Turned out that I could do the whole she bang with just the internal pump on the 110... a 60 with an external ECM would have been even sweeter although the MCBA on them is much more locked down it seems.

Research and understand... and respect your contractor foir what they do and the work they'll stand behind and don't worry if they don't have more hours to spend in here researching like we do.

If you do get a Prestige, get the Smart 50 tank and a mixing valve so that you can have it run with a wide on and off temp differential. Otherwise, and especially in the summer, the hottest 2.5 gallons of water will get stranded in your HX and eventually those BTUs go up your chimney. The fewer DHW cycles the better in the summer... in the winter even a wide diff and lonfer DHW runs shouldn't affect things.

One zone and piped direct will keep your electrical costs way down compared to other solutions and the MCBA can provide partially cont. circulation for maximum comfort with sky high electrical bills.

Best of luck...

 

Some thoughts.

1) If the pipes are inside the house, piping loss is irrelevant to boiler sizing. The heat they give off still goes into the structure. Even if they're in the basement (and if you want a colder basement, just insulate the pipes...). Outdoor reset and the nearly constant circulation a modcon system will have further stabilizes the mass of the system. If your heat loss is 54,000, don't get a boiler much or any bigger than that. Certainly not double. Even if it's a modcon. The problem with oversizing a modcon is that the low end of the modulation range on the larger models often exceeds your low- to mid- condition heat loss. That means the modcon will short cycle, and/or spend a lot of time sitting on its lowest firing. Nobody's sure whether that's good for the long-term health of the boiler. Probably not.

2) I feel very strongly that you are buying a service from an installer. What you are paying for is his skills. They have to make a buck, and the good ones are richly deserving. Some make their money on an install through labor charges. Some mark up the equipment (although in this day and age where everyone can know the price of everything, I think that's foolish). Some do both. WHATEVER. If the guy is good, it doesn't matter what you are paying for labor or equipment. Look at the total price and if he's good, write the check. He makes his money, you get a quality system and a reliable, quality contractor.

3) In part because of 2 above, when you start talking about "well, I can get the boiler for $500 less than you," you run the risk of rubbing the installer the wrong way and he's outta there. Again, it's not about how he chooses to make his money (labor or markup). It's about what you are going to pay for the total job.

 

Thanks again for your input. I understand completely what you are saying about the professional int he person I am hiring. Having come from that background (Dad was a contractor), I have a strong respect for anyone who does a good job and works with what I want. Sadly, it has been an ongoing struggle in this area to find that person. It seems when the economy tanked here in the 80's-90's all the quality guys headed out, with the exception of a few. They are still out there, but you need word of mouth to find them.

Anyway, I will hold my ground on the boiler sizing and await to see what the estimates come in at.

Thanks!