Homeowner questions

[Deleted User]

I am looking to replace my current gas boiler (30 yr old 171 btu Dunkirk). Before I did a complete heat loss I added up all my baseboard and multipled by 500 for a rough idea. I got 88k. Could the boiler be that over sized? I was hoping of a Weil-McLain utlra and have a few questions.

1. When looking at the DOE cap is that what I can expect or is it the eff. x DOE? Ex. the 105 has a doe of 94 and a afue of 92, does that mean it will be undersized (94x.92=@86). I havnt priced both so dont know how much of an issue it is.

2. Savings of a modulating boiler. If comparing 2 boilers, one non-modulating 85AFUE vs a modulation 95AFUE, can I expect more that just 10% saving with the modulating boiler since it wont always be at max capicity, right?

3. Since I'm working with a budget(aren't we all) I would like to buy the "best" boiler possibe, so I would like to try to install it myself. Am i crazy? Is there anyone willing to "mentor" me in the Stonybrook, NY area. Since it is not an emergency, it could take weeks, and i will do the grunt work.

4. Should I consider other boilers? Muchkin/pinnicale?

Thanks,
-Mike

Constantin

Here are some suggestions:

IMHO, the best way to determine how much energy your house loses on a given day is to compare the gas consumption during the winter months vs. the degree days that you have experienced in that month. The degree-day data is available in many newspapers and/or NOAA. Next, simply convert the therms, ccf, or gallons of gas used to BTUs (100kBTU per Therm, 103kBTU per ccf of natural gas, 91.6kBTU per gallon of Propane).

Once you know how much energy you lose per degree day (i.e. divide total gas consumption by degree days, remember to account for system efficiency), you can calculate the maximum heat loss using a design day. In Boston, a design day (-15°F) is equivalent to 80 degree days (the difference between 65°F and the design day temp - thanks for the correction, Chuckles). Multiply the results out and you should have a fairly accurate for what IBR rating your boiler should have.

As a fellow homeowner, I have followed the discussions on the Wall for a while and have seen many instances where boilers were oversized by previous installers "to prevent callbacks". The issue of oversizing becomes particularly egregious once people start insulating and weatherizing the home, all while the installer keeps plunking the same size (or larger) replacement heating system in the basement. Frequently, it appears that replacement boilers are not sized to the home but rather reflect what the local supply house or installer have in the warehouse that day.

Some members of the Wall community will tell you that using a condensing boiler with baseboard is a bit overkill, as whenever you hit colder weather, the required water temperatures will rise to a point where the unit will no longer condense. My counterpoints to this line of reasoning are that the very cold conditions are relatively rare, the shoulder seasons are much longer, and that most home installations have far more baseboard than they actually need (thus allowing lower water temperatures).

The DOE vs. IBR ratings, etc. are a safety margin, IMHO. Thus, if a boiler has a input rating of 100kBTU and a efficiency of 92%, then the DOE output is 92kBTU. The IBR rating is derated another 15% to account for losses along the way (i.e. ~78kBTU net available). I would consider the 15% a safety cushion, unless the pipes run through exterior walls (never a good idea). So, match the the actual max. heatloss to the IBR rating and you should be good to go.

Savings from modulation depend on several factors, one of which is whether you plan on using a sophisticated controller strategy. I advocate the use of outdoor reset as a first step. A modulating burner will allow you to increase comfort within the home by matching the heatloss of the home perfectly. The lower the water temperatures required to heat the home, the greater the energy savings. Outdoor reset makes this possible and may save you up to 25% on your heating bills.

I would NOT attempt to install a sophisticated boiler without the training and experience that is required to do a good job of it. While there are a number of internet companies that would like you to believe otherwise, the many hack installs you can marvel at here and on the Wall of Shame at HVAC-Talk, tell a different story. Instead, try finding a professional that may allow you to participate.

At the end of the day, as best as I can tell, the Munchkin, Pinnacle, Vitodens, Quantum Leap, etc. are all fine condensing boilers. I would look for one that your installer is familiar with, has installed before, and is happy to service. Ultimately, any boiler system is only as good as the person that installs and maintains it.

Chuckles_2

> you can calculate the maximum heat loss using a

> design day (-15°F in Boston, for example).

> Since we expect our indoors to be comfortable, a

> design day will thus result in 85 degree days

> (70°F indoors, -15° outdoors, the

> difference is 85°F). Multiply the results out


The standard definition of degree-day is the number of degrees by which the average outdoor temperature is below 65F (NOT 70F). Experimentally, gas demand from utility companies (i.e. averaged over a large number of homes) consists of a weather-independent baseline plus a part that is linear with outdoor temperature; the linear part extrapolates to zero at 65. Other sources of heat in houses (lights, cooking, warm bodies...) are probably what causes this shift.

RoosterBoy

DO NOT INSTALL THIS BOILER YOURSELF
PAY THE PROS AND DONT JUST GO FOR THE CHEEPIST
AND ASK FOR BRANDS AND RECOMENDATION FROM THIS WALL

i came to this wall and asked for advice on a good boiler and i am haveing a buderus installed by a good contractor
he was not the cheepist but i only want to have it done once

good luck

Chuckles_2

yes

> I am looking to replace my current gas boiler (30

> yr old 171 btu Dunkirk). Before I did a complete

> heat loss I added up all my baseboard and

> multipled by 500 for a rough idea. I got 88k.

> Could the boiler be that over sized?


Yes, it could. But measuring baseboard is not a good way to size a boiler. Look at the post by Constantin about how to use your gas bill to size a boiler.

>

> 1. When looking at the DOE cap is

> that what I can expect or is it the eff. x DOE?

> Ex. the 105 has a doe of 94 and a afue of 92,

> does that mean it will be undersized

> (94x.92=@86).


No. 94 is the output BTU.

> 2. Savings of a

> modulating boiler. If comparing 2 boilers, one

> non-modulating 85AFUE vs a modulation 95AFUE, can

> I expect more that just 10% saving with the

> modulating boiler since it wont always be at max

> capacity, right?


There are a lot of reasons why real-world savings differ from the AFUE. You can do a search on this board to find previous discusssions. No one can say how much you will save due to modulation; it depends on the situation.

> 3. Since I'm working with a

> budget(aren't we all) I would like to buy the

> "best" boiler possibe, so I would like to try to

> install it myself. Am i crazy?


Yes.

Constantin

Thanks for pointing that out.

I thought it was 70 degrees... I stand corrected. Cheers!

Jim_44

DIY install?

Mike, Take it from a homeowner for the sake of you and your family DO NOT Take it upon yourself to install your boiler. There are so many factors involved and i will mention just one - CARBON MONOXIDE. A Pro (not the ones wearing a short skirt) will make sure it is installed and tested right. You will pay once to do it right, but you may pay forever if it is not. Jim

S Ebels

Mike

I don't know your financial circumstances Mike, and I am not pointing a finger directly at you. This little rant is aimed at a large group of people who want to save some shekels. In fact, to all homeowners who read this, forgive me for being blunt but I have to say it. I'll use Mike as an example only because he's here. That preface being stated...........

I think it's insane to try to pinch pennies on a heating system. Your heating system can run as much as 2-3,000 hours per year depending on a number of things. Convert that into miles traveled in your car at an average speed of 40MPH. That my friends is a LOT of run time. I think it's insane to compromise the installation in any way shape or form.

What's the problem with "saving money" and DIY or even hiring the low bid? 99 times out of 100, any money you save quickly evaporates into failed equipment due to improper installation, higher than needed utility costs, poorly performing systems that don't heat correctly, etc.

Face it. A lot and I mean probably over half of the contractors out there don't know how to install a new condensing boiler correctly. How's someone who does this once every 20 years or maybe once in their life going to know? It is NOT just a matter of screwing pipes together. You have to know how the equipment is designed and what type of system it works best on. Condensing equipment is way different than the old iron boiler you now have. You have to be able to compare in your mind what is going on as opposed to what should be going on and make appropriate corrections if needed. This is something no-one who puts in one or two boilers in their lifetime can do. Someone who does not work with this stuff everyday does not have that frame of reference to work with.

That being said; what's the big deal with going out a getting a 5 year note to pay for an excellent piece of equipment and a good professional installation. I see people borrow funds all the time for frilly stuff like a snowmobile, boat, furniture, floor covering, siding their house. When it comes to the furnace or boiler there seems to be a conception that you just use what money you can scrape up and that's what your budget is.

Let's look at the numbers. Say you buy UBER' Boiler XYZ and hire the primo contractor in town to put it in. Let's say you get HeatBoy to put in one of his diamond plate installs and the whole shmeer is going to cost $10K. Borrow that with nothing down at a rate of 5.5% on your home equity line and you'll pay a total of $11,460 over 60 months. Payments would be $191.01 per month and the total interest paid is $1,460.70 according to MS Money. All of this interest is a tax deduction BTW.

Now, to all of you contemplating installing a high efficiency, boiler or furnace for that matter, do you realize that it is possible to spend the amount of interest paid over the life of the loan on one service call to correct an improper installation?
Do you realize that a reduction of efficiency of just a couple % can cost you the equivalent of 1-2 months payments on your system every year?

Now, more-so than ever, with oil at $55 a barrel, your heating system should be looked at as an investment. A long term investment. Unless you have a crystal ball or direct pipeline to Saudi Arabia you have no idea what you will be paying for fuel in the over the life of your heating system. Why on earth would you not desire to have the BEST equipment, installed in the BEST manner, by the BEST people you could find.

Sorry if I offended anyone. That is surely not my intent. I just can't fathom the myopic view that most seem to have about energy consumption, what affects it and what the future holds as far a prices are concerned.

Buy and hire the best and you'll very seldom be sorry.

End Of Rant

Constantin

Hear Hear!

That was well put. In fact, if you go through the energy-star, etc. web-sites on the web, you might be able to find banks that make loans specifically for home-improvement projects like better boilers, insulation, etc.

Chuckles_2

One objection. Whenever taking any advice, one has to consider the source. I assume you are a seller rather than a buyer of boilers and installation?

It simply isn't true that if you spend more you get a better install. Pricing is a gamble on the part of contractors, and different contractors gamble differently. Of course there is no way for me to do two different installs in my home at two different prices and compare the results, but some of the highest quotes I have received have been from contractors who didn't know much. How do I know? From reading the Wall. Some of these guys were the big operations, the ones with full-page ads in the yellow pages.

So my advice would be not to go for the high price, but to learn as much as possible before getting quotes. Unfortunately hydronics is a field with a lot of incompetent contractors, and no, they don't all give the lowest quotes; some of them give high quotes because they are looking for the easy money.

Of course I agree that the OP is crazy to consider doing the install himself.

Jim_44

Boiler $

Forget about the banks. Use your house to get a home equity line of credit which I think is at about 4.25% and have your boiler done by a competent installer. Thats what I did. JIm

S Ebels

I used

5.5% just to be on the conservative side of things. It's a habit of mine that comes from being raised in the Midwest. We can't help it. It's like a birth defect or something.