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Switching to gas, trying to size a water boiler

JustinrazJustinraz Member Posts: 11
Hi All,

We bought a house last year. The oil killed us, and we had an opportunity to add gas to the house cheap. I would also like to have more space in the basement (big oil tank there). I have been trying to size, a boiler, and would like some opinions. Quick run down, I will describe the best I can:

House was built in 1911
It is about 2000 sq ft.
Outside construction is stucco
Inside walls - some are plaster/lathe. Some plaster/lathe with paneling over them.
Drop ceiling (10ft)
Most of the windows are updated in the last 5 years. About 10 are not, but they are in good condition and not drafty.
Finished basement, finished attic (bedroom)
Baseboards are in the basement, attic, and a front add on room.
5 rooms on the first floor
3 rooms on the second
All other rooms are wall mounted low cast iron radiators.
Current oil boiler is a Trianco HC-175 - 175 mbtu gross output/152 net output (I take it this means 175000 btu) I think it was installed about the early 1990's.

From my calculations I seem to need to be at 88,000 btu. I will have four floors to heat. We may add a small room down the road. I was thinking of going to 100,000.

Does this 175 seem like it is oversized? Is there other factors I should take into consideration? I am up in the air about whether to go conventional or something energy efficient.



  • SWEISWEI Member Posts: 7,356
    If your load calc is even close to correct, you want 88k (possibly less) of DOE output capacity. Any plans to insulate the walls? Is the attic insulated? Might it be later?
  • JustinrazJustinraz Member Posts: 11
    No plans as of now to insulate the walls. They don't seem to get cold. I assume the attic is insulated since it was renovated to be a room. It has paneling on the ceiling, so isn't the normal ceiling. It holds heat well. Not sure if it's because it is insulated or because heat rises.
  • JustinrazJustinraz Member Posts: 11
    I also forgot to mention I am in lancaster, pa. So we have winters, but nothing like some areas.
  • JustinrazJustinraz Member Posts: 11
    The installation, and maintenance is no worry. My cousin has been working in the HVAC field for years. He has done a lot of work for my friends, family and myself for years and everyone has been extremely happy. He is great with installs, troubleshooting, and what not, but talking with him on what to go with, I think he lacks the sizing skills. His suggestion was 100,000-120,000 because of the possible addition.

    Right now we keep the heat at 62-64 degrees. I think 66 will be fine if that is the worst case scenario.

    I hate dealing with contractors. When my auto delivery expired, the company asked if they could give me a free quote, and I said sure. I don't mind hearing other peoples tips and tricks for free. Since he was an oil guy, he was giving me hell on how much gas was going to be. He said that most people using gas were paying on average $200 in the winter months last year. I showed him a bill his oil company sent me in July for budget billing, he quickly shut up. I don't even go through a quarter of a tank between April-October. From what I paid last year, I would gladly welcome those kind of bills. Maybe I jumped the gun on going to gas, but depending on what boiler I go with, I should make my money back between 3-5 years. I don't plan on moving again so I will invest in something good.

  • bob eckbob eck Member Posts: 915
    How many zones?
    How do you make domestic hot water?
    Are you looking at using a conventional cast iron gas boiler with a indirect water heater or a tank type gas water heater or a tankless gas water heater or a condensing gas boiler with a indirect water heater or c condensing combi boiler?
    How is the boiler going to be zoned.
    I work for F W Webb Plumbing and Heating wholesaler in Allentown PA. We do heat loss design from 0 Deg outside temp to 70 Deg inside temp. Have your new system designed so it can maintain 70 Deg inside temp even if you are going to keep it at 66. Deg or less. When you sell the house the new owners most likely will want the house at 70 Deg in the winter.
    seems like your oil boiler is way oversized and it must short cycle (very short run time) and this waist oil costing you money. Does your oil boiler have a domestic coil in it to make domestic hot water. This also uses a lot of oil to keep you boiler hot 365 day per year just for domestic hot water.
    A good low mass oil boiler sized right for your home like our Trio oil boiler and Purepro indirect water heater can lower you oil bills big time if you want to stay with oil. Your new gas boiler needs to be sized right to keep it from short cycling wasting energy. If going with a condensing gas boiler you need to make sure you have the type of system where you can run lower supply water temps and still heat the home and bring back low water temps below 135 Deg to make the boiler to condense and get as much energy out of the gas and then this boiler can run at 90% efficiency or higher. If your system can not make the boiler condense a high efficiency condensing boiler efficiency falls off and has efficiency about 82% - 85% regular cast iron gas boilers efficiency is 84%
    Make sure you get the best system for what you can afford.
    Remember it costs more to do it twice than to do it right the first time.
  • icesailoricesailor Member Posts: 7,265
    If the size of the oil tank and the space the oil tank takes up is a consideration, it must be a small cellar. 10 Sq. Ft.?
  • icesailoricesailor Member Posts: 7,265

    You mentioned 88,000 BTU loss on the design day. Did you utilize the fact that you keep the heat at 63 degrees? The heat loss calculations generally use a value of 70 degrees as the indoor temperature. This would have a dramatic impact on the size of the boiler.

    Since you have someone that is familiar with HVAC and can properly install and service a mod-con (no easy task), that is the direction you should seriously consider. Their capability of modulation and the use of outdoor reset as standard equipment gives them a significant edge on the conventional equipment.

    What do you have for hot water? Will the new unit need to provide for hot water?

    I don't know if you live on the outer banks of North Carolina, but winter cold and heat loss are a different animal to the NW of you.

    I doubt that the house has a lick of insulation in it, and the homeowner isn't planning on wasting his hard earned money on any stupoid insulation. When he can install a smaller, more efficient (undersized) boiler in his house and complain about being cold when that Artic Vortec moves down after one of those massive Nor'Easters goes by that develop off your Cape where all the warm Gulf Stream kisses the shore.

    You need to accept the fact that a lot of homeowners with newly purchased property watch far too many DIY and Home Improvement shows with "Experts" ("X" is an unknown quantity. "Spurt" is a drip under pressure) and their OCD (Obsessive Compulsive Disorder) kicks in because their brain is connected to the sounds of a burner running. And equate it with their hard earned cash being blown up the chimney. When in fact, the sounds of burners actually relate to the flow of heat energy through the walls to the cold outside.


  • GordyGordy Member Posts: 9,523
    edited December 2014
    I agree with others use 70* for heat loss calcs. I think you will find that set point creeping higher when the heating bills go,way down. Those calcs are padded by a margin also 10-15%.

    Also you might have to line your chimney going to gas and a smaller boiler which has a lower flue temp than oil. So condensing may become an issue. This adds dollars. Which might make the venting of high efficiency attractive, and comparable in cost by the time you add a liner to the chimney. Check local codes on this. It all depends on chimney size, and detail of its construction.
  • icesailoricesailor Member Posts: 7,265
    Justinraz said:

    No plans as of now to insulate the walls. They don't seem to get cold. I assume the attic is insulated since it was renovated to be a room. It has paneling on the ceiling, so isn't the normal ceiling. It holds heat well. Not sure if it's because it is insulated or because heat rises.

    That is the absolute worst way to decide if you need to insulate your walls.

    A better way is the old third world Yankee way. Put your hand on any outside wall and lean against your hand on the wall. If the wall doesn't get warm and/or the palm of your hand doesn't start feeling warm, there is little or no insulation of heat resistance in the wall cavity. If you have one of those cheap Styrofoam coolers, do the same hand trick on the cooler, and note how fast your hand feels warm. That's the heat being lost through your warm hand, being radiated/reflected back.
  • icesailoricesailor Member Posts: 7,265
    @bob eck:

    Bob, not to single you out, but because you work for a major wholesaler that I had/have an account with, I will tell you up front. You and your Compadres are why I learned to do my own heat loss calculations so I understood what was the intent. Every wholesaler I used came up with different numbers, supposedly using the same sets of rules.

    As long as you don't promote energy loss reductions like insulation and weather stripping, in my opinion, YOU all should be getting that erroneous blame given to oil companies setting up burners to burn more oil.

    Putting more efficient boiler or heating/cooling equipment in inefficient buildings is a huge waste of money and energy.

    You guys spec and have installed these glorified coffee makers, and then, on a cold windy day, the house is cold. You go to look at the house on a cold windless day and all is fine. You get that "Deer In the Headlights" look. All seems right to you. You spec'ed an undersized boiler and the contractor (who should have known how) didn't do an accurate heat loss and understand what he was dealing with in an old house. No accommodation for those high wind infiltration/loss factors.

    You think I don't know what I'm talking about? I've been in the trap. Fortunately, because of my knowledge of construction techniques, I could figure it out and get something that wasn't my doing, resolved.

    My son's Grandfather In Law built a large brand new house. State of the art. He was an old Plumber after the War, before he started another successful business unrelated to plumbing. But he always kept his hand in it. He had the house figured by one of your competitors. My son came to me and said he thought the boiler was way too big, but it was what Gramps" wanted and the sales person insisted. It was a WTOG-6. I told them it was way too big, that a WTOG-4 would probably be too big. After one PO-ed salesperson was done, (I had an account with this company), we settled on a WTGO-5. It was no skin off my butt. I had just built a similar sized house that heated fine on a WTGO-3. Even so, I down fired the WTGO-5 to 1.00 GPH and had spectacular numbers. Do you have any idea how well a oil boiler will run on Road Diesel? You almost don't have to ever change filters, and when run as a warm start, you only have a light brown ash to buff out with a nylon bottle brush. No Gray and Black Kibbles & Bits.

    You can buy and get away with a underpowered automobile. Don't put fur people in it and expect to drive at Interstate Speeds. It won't happen when you hit the hills. And the brakes overheat when you go down the hills.

    Just to set the record straight about "Beer Cooler Boilers", there is a movie with Gene Wilder and Richard Pryor called "Silver Streak". Richard Pryor makes a comment a few times when he is really impressed by something, that might be censored here. But it covers my feelings about those boilers in a proper application. I put in as many as I could. I loved them. In the right application. And the right size.
  • JustinrazJustinraz Member Posts: 11
    edited December 2014
    I really do appreciate all the help, advice and ideas. It gets overwhelming trying to research all this online. I'll take your suggestions and redo my calculation.

    For the insulation concerns. The house holds heat well. I have no issues with the house staying warm. I keep the heat at 62-64 degrees, and the rooms will hold heat for hours and hours. Our bedroom had four old leaky windows, and the living room had two. I replaced them this summer, and I notice a difference this year. I was looking into what I could do to insulate better, but the gas company had a deal of "We will install gas up to the house super cheap, if you connect within a year." It was normally $3500 to install, I paid $400. If I do not connect, I will have to pay the difference.

    My average oil bill last year was $368 a month (12 month budget plan) at 62-64 degrees, I think I can do better than that. Even with gas I'll keep the heat at the same range. The goal is to have my gas bill be an average of $80 if not less, instead of $368. Friends with houses about the same build, size and less updates with gas had way better bills than mine, and they kept the heat at a higher range. Friends with houses about the same build, size and less updates with oil paid slightly less. The boiler is from the early 1990's, and the tank is newer (see picture).

    See below for some follow up answers to previous posts.

    It is one zone. I'll ask my cousin how hard it would be to go to two zones. The second floor (2 bedrooms, 1bath), and attic (3rd bedroom) only really need heated at night.

    When I did the calculation I did it at 68 degrees.

    The boiler itself does the dhw. I plan on something different. I was thinking gas tankless. I barely use any oil between April to October for the hot water. Maybe I will hardly use any gas.

    As for what boiler to go with, my cousin suggests to stick with a conventional, and add an external water heater. My cousin likes to keep it old school. He has said there is a lot of new nice stuff out there, but it obviously can cost more. The quotes he gave me so far, I can add a good conventional boiler, and a good indirect water heater for fairly cheap.

    I would have to line the chimney if I want to vent that way. Again my cousin said he can get me a liner cheap. My neighbors who just added gas, and already installed their gas furnace have the direct vent to the outside.

    The basement is big, its just that I could use the space where the oil tank is for something better.

  • icesailoricesailor Member Posts: 7,265

    "" Remember, you need a boiler, a chimney liner, an indirect, and all the proper controls and piping to allow the boiler to function with the indirect, including the controls to prevent low temperature return water, and including the controls to prioritize the indirect. ""

    The Taco "I" Series 4 way does every bit of that for a fraction of the cost of anything you can come up with.

    You /I could throw a I series 4 way on that system and see an immediate increase in comfort and a drop in cost. Because he is already planning to switch to gas, he will be needing an indirect. Even with the way it is, he could still leave that as is with the Tankless and still use the I Series valve. Or install a storage tank on the tankless. The I Series maintains a warmer or hotter boiler temperature while mixing the system temperature to whatever is needed in the moment. Don't think I don't love Mod-Cons. I love them. I loved fixing them. It was always a challenge. Don't ever put something in front of me, tell me that it doesn't work, and ask me to fix it. I'll be on that like a gang of stray cats finding an unexpected feed. I would be in the Supply House and listen to all the tales of woe about the Mod Con problems. Those same problems never seemed to be as bad with higher mass, less technological equipment. I didn't mind selling it. I HATED it when some customer asked why I sold them something with so many problems and why should they keep paying for something they considered junk. I never enjoyed that question like some must. But I never did.
  • icesailoricesailor Member Posts: 7,265

    "" Sadly, "cheap" in this business usually fails the performance test when all is said and done. "".

    It depends on how you define "Cheap". Just because something cost less doesn't mean it is "Cheap".
  • GordyGordy Member Posts: 9,523
    You forgot about lining the chimney ice. You don't need that for a mod/con. I think that and an I valve puts you more than a mod/con with all that on board. Liner is a variable since we know nothing about chimney size.
  • JustinrazJustinraz Member Posts: 11
    Well when I say cheap I mean at cost. Not cheap as in manufacturing. I notice these forums do not like to discuss pricing. Hopefully I do not overstep with these next statements. I can get a Burnham boiler for a discount (my father works there). My cousin can get me something from a supply house at a reasonable price. Whatever the price is on the internet, I can get it cheaper through him. I will have no labor fees.

    I have no plans on moving, so I would like to make the best investment I can. My cousin is always on the fence about the new stuff. He said he has a lot of service calls on them. This is just something I will have to workout on my own.

    He also did mention about putting some valve in to help during the summer/winter time for energy savings.

    From some basic forum research I have read that houses in super cold regions that are bigger, older and not as up to date use heating units in the 70k-100k range.
  • R2.0R2.0 Member Posts: 99
    Have you looked into a conversion gun for your existing boiler?

    I recently did the exact same thing as you, converting from oil to gas. When I did my calcs I found that my existing boiler was substantially oversized. You might also want to do your calcs using a couple or 3 different methods, just as gut checks.
  • icesailoricesailor Member Posts: 7,265
    You can easily "downfire" a larger boiler. The limitation is when the boiler is so big that it doesn't support good combustion.
  • icesailoricesailor Member Posts: 7,265
    Its all in the List and the Net. What we sell it for, and what we buy it for.

    Some people think that profit is an obscene concept, and Overhead is a ceiling. Someone has to pay my expenses. Or, I might have just as well gone back to my old boss. But he's dead.

    I owned every tool I used. Some don't own anything but a hammer. They lease a truck and rent equipment. Someone still has to pay them enough to get to your job.
  • JustinrazJustinraz Member Posts: 11

    I ended up going with a Burnham ES2 105,000 btu, with a 35 gallon Alliance Indirect Water Heater. The install on the gas boiler went smooth. The indirect, not so much. Once we had the plumbing everything down, we started to hook up the power. No light on the TPI thermostat when the 24v was hooked up, and the circulator wasn't running. After some troubleshooting, it looks like the TPI is bad out the box. We get hot water when we wire the circulator to run constantly, so we know that works. I'll put pictures up once everything is set correctly.

    I also got the LCD panel with outdoor reset. Will install that at a later time.
  • Paul48Paul48 Member Posts: 4,492
    I was in a similar situation as you. The $420/month year round for oil was the last straw. My chimney was already relined, so I was ahead of the game. I went with a conversion burner, and the savings paid for it the first season. I cut my bill in half, and come out of each heating season owing nothing.
  • JustinrazJustinraz Member Posts: 11
    Paul, that is great. Did you do anything else to help cut it down, update windows, or insulation? I still need to do the liner. I have one, someone, not me, just need to slide it down.
  • j a_2j a_2 Member Posts: 1,796
    Hi. If relative is a HVAC guy he must know how to size a boiler, please....Not all as stated above oversize, only the ones that are in over there head do...I B R uses hr 22 its a great form for a true heat the I B R book and read can purchase it here...Me I say cast iron with a poor mans outdoor reset....A BOILER BYPASS
  • Paul48Paul48 Member Posts: 4,492
    No windows or insulation. The boiler is oversized, they down-fired it about 15% with the gas gun.
  • j a_2j a_2 Member Posts: 1,796
    Did I miss something or is this oil...are you referring to this thread....I don't personally like down firing that much. H O. Stat away from thankless gas boilers for domestic hot water... Look into hybrid electric or better yet straight up 40 or 50 gallon water heater.
  • JustinrazJustinraz Member Posts: 11
    So the issue with the IWH was the wiring schematics from Burnham are a little whacky. Also the examples they provide are a little goofy. Tech support is superb though. Everything works the way it should.
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