I would go with Viessman or Buderus. Viessman are the best...but the price is also up there.

A 100K BTU boiler seems large for your house. Boilers need to be sized by the heat load and the number of radiators. Find someone who knows how to size the boiler properly.

Concentrate on the brands that are common for your area. You want a local contractor who can service it and get parts.

Are you installing the gas hot water heater in an unheated garage? That is not going to work on Long Island. If you are going to make a conditioned area for it, then you need to supply combustion air. Think this through carefully and get a permit for whatever you decide to do.

@mike_home That was my concern. It's an uninsulated garage and I haven't gotten a chance to speak with the plumber yet. My plumber said he has installed Burnhams, Rianni, Navien and other for oil. If this was your house, what would you do? I've had 5 different plumbers come in to give estimates and opinions and they all differ greatly in their recommendations and brands. I am completely lost now and have no clue what brand. I think I finally settled on a plumber (he was the only one that actually took some measurements and walked me through my options). The others just looked up and down and gave me a quote with what they wanted to put in.

@malba2366 Have you worked with these or are you a homeowner that has them?

I am not a boiler expert, nor ever purchased one. So I can only give you some general guidance and my opinion.

If you intend to buy a basic gas fired boiler, than I don't think you have to loose sleep over the brand. Boilers have no moving parts and last a long time. I suppose a boiler could crack but I think that is caused be either by abuse or improper installation. If you were in the market for a state of the art combination boiler that I see Rich Trethewey promote on This Old House, then you would have to be concerned about brands and reliability.

Don't spend a lot of extra money on upgrading the equipment so you can get a rebate. Most of the times it is not worth it. You are going to save a lot of money just from converting from oil to gas.

If you have found a contractor who spends time taking measurement and explaining options to you, then you have a good chance of getting a good installation. I would put him at the top of list. Hopefully he installs a brand of equipment that gets good reviews.

Installing a hot water heater in an unheated garage is a bad idea. A 50 gallon tall hot water heater has a small footprint and minimum clearances to the wall. The new gas boiler has to be smaller than the old boiler and oil burner. Maybe you can fit the new equipment is the same space as the old?

Another option is a tankless hot water heater. It is more expensive than a tank version, but it can be hung on a wall. It will require some maintenance that you may be able to do yourself.

Does a tankless hot water heater do the same thing?

I don't currently have a hot water heater in my house. We have an oil burner in the laundry room and that's it. We wouldn't have the space to put a new boiler AND indirect water heater in the same spot. It wouldn't fit. So now I think I am back to square one...seems I need a combi unit then. Any recommendations on that?

it seems like an easy question, but the answer may not be if you want to be sure that you put in something that works. It is not rocket science, but takes some time. You have all summer to do this, but get started now. Just to get started:

Yes, you need to match the boiler to the heat emitters. Baseboard is not all the same, however. Aluminum fin needs much higher temp water than cast iron. Heat output from the former is not linear with respect to water temp. The latter radiates the former convects. You also need to match the boiler to the overall heat loss from the house. It is OK to have too much emitter. In fact, for pure heating reasons, it is darned near impossible to have too much with higher efficiency boilers. It is not OK to have too little emitter for the boiler or too little to keep your house warm. The former happens all too often. The latter is not likely unless you cannot get away from wearing your coat indoors all winter. Too little emitter for the boiler is like trying to have them drink from a fire hydrant of a boiler. Too little emitter for the boiler will result in nasty short cycling and this becomes a much bigger problem when installing a low mass boiler in place of one that is loaded with cast iron and lots of water in the heat exchanger. Lots of mass gives you a safety margin in that respect, but it is still bad to oversize. Oversizing will hit you hard with a typical high efficiency boiler resulting in not near the efficiency you expect and possibly, short life.

Combi boilers are even harder to match to an old system than others. Unless it is very small house with limited hot water needs, or an apartment, I'd stay away. Where is your boiler now, in the basement? I am confused unless you have an existing oil boiler in the laundry with two heat exchangers, one for DHW and one for space heat. Oh, boy. That is probably a hot-start boiler that heats your house year round. You are going to love getting rid of that heat source in the summer.

There are lots of engineering calculations to be done. Emitters, pumps, and boiler. I would not be scared of high efficiency, but it has to be done right. The return water has to be cool enough to condense. Right now, you probably have your boiler set to about 180 and the return water is at 160 or maybe 150. With a new boiler, you may have to repipe to protect the heat exchanger from cold water coming in when it starts up. That's called primary-secondary piping. Some modern boilers, however, have it built in.

An old home with lots of insulation, window and door and general air sealing improvements is a big boon to installing a condensing boiler as long as the original emitters are still intact. You can turn the water temp way down and still get enough heat out of the rads, especially if they are cast iron.

You can do a lot of the necessary calculations yourself. You can figure out what kind of radiators you have and measure them (The finned part if you have that type) to calculate heat output. Heat loss is more time consuming, most measure the home extensively, determine insulation properties and guess on air infiltration. You can probably make better estimates from fuel use, boiler efficiency and weather conditions. What other oil appliances do you have? Get degree day information from your local weather station and fuel use going back a few years if possible. Dead of winter numbers minimizes error due to DHW production. Where are you located? Long Island has a very mild climate compared to St. Regis Falls.

Scoot over to heatinghelp.com, "the wall" and Terrylove.com. There are lots of serious boiler heads over there that offer patient explanation and generous help with boiler decisions and even DIY heating system for new builds and renovations. As I indicated, this is not rocket science, but if the time is not put in, you will probably get a bad boiler installation. Note that boiler, radiator and pump manufacturers often help the installers pick the right equipment and even go to the house to help them measure and calculate sometimes.

If expert help is not available, and even if it is, your best bet might be an HTP Versaflame or Versahydro. They have an ingenious heat exchanger that takes advantage of the natural polarization of water of different temperatures. They will be the least sensitive to screw-ups in the rest of the system. They are high mass boilers and the mass is water. They should drop right in with trivial modifications to the existing remainder of the system. These are the only combi boilers that I would consider for a "regular" US home retrofit. They have flat plate heat exchangers and pumps to separate the space heating water from the DHW. They are high efficiency, turndown (5:1) boilers.

If your heat demand is low enough, a great economy economy move might be a Westinghouse water heater in the WGR060NG076 series. They have the same design heat exchanger as the HTP boilers and HTP Pioneer water heaters, but have a 3:1 turndown ratio. You can buy one for less than $2000 bucks and it will drop right in with no serious plumbing mods and work well. It is not a combi boiler so you would need a second one for that, or the plumber can install a heat exchanger. Depending on the set up, a second, indirect, tank might be desired for DHW. This, however, might cost more than installing the Versa. The Versas should qualify for a rebate, but the Westinghouse will not.

Lastly, look into the NYSERDA program. home mods are income based, but I think that anyone can get a free home energy evaluation including a blower door test for air infiltration. The energy rater will measure your rads and calculate heat loss. (I'd still do the fuel use cal just for comparison.)

Good luck.

@ionized_gw Wow...thank you for all of that information.

"Combi boilers are even harder to match to an old system than others. Unless it is very small house with limited hot water needs, or an apartment, I'd stay away. Where is your boiler now, in the basement? I am confused unless you have an existing oil boiler in the laundry with two heat exchangers, one for DHW and one for space heat. Oh, boy. That is probably a hot-start boiler that heats your house year round. You are going to love getting rid of that heat source in the summer."

The current set up is a house with no basement (on a slab) with a boiler in the laundry room. As for the heat exchangers, I do not know. It seems like you know what it is. It does kick on all year when we need heat or hot water. If some one is showering it kicks on, same when hot water is needed for the dishwasher or washing machine. It's terrible but that's what was in here when we moved in a few years ago.

"Where are you located? Long Island has a very mild climate compared to St. Regis Falls."

I am located on Long Island and I do have the aluminum slant fin baseboard heaters.

You seem to be VERY knowledgeable about this topic and I thank you for taking the time to break it down for me. I'll see if I can get an energy rater to come in and do the necessary calculations. Assuming I got an indirect tank for DHW, can that be installed into an uninsulated garage if I moved the entire setup?

@ionized_gw HTP has discontinued the Versaflame but they have the versahydro. Seems like a great product. Would you go with that over the HTP UFTC-140 combi unit? A lot of people say the Viessmann VITODENS 100-W is a good quality product as well. If it was your home and you had 3 kids (7 and under) that will be taking baths and showers for along time which would you go with? Again, it's 1900 square feet on Long Island that uses baseboard heating (aluminum slant fin) with 2 bathrooms in the home both with showers and the regular needs of a washing machine and dishwasher.

You need more help than I can give you. All I did is guide replacement of a 50 YO cast iron boiler in my father’s home. It was a combi boiler probably much like yours, but he had more space. In your situation, you might have to settle for a combi unit. Strides have been made to eliminate the hated cold water sandwich that they generate with repeated turning hot water on and off (think shaving or rinsing hand-washed dishes). Check int the NYSERDA program and surf on over to the links that I suggested. Read up on boiler posts and ask questions. I doubt that having an indirect tank in the unheated garage is acceptable and may be contrary to building code.main difference between the -flame and the -hydro is what is powered by the water in the secondary heat exchanger and what comes from the primary heat exchanger/buffer tank. You end up losing about. 20 degrees F in the secondary exchanger so lower water temp is available. They are somewhat redundant, but the primary water temp has to be as low as practical for condensing efficiency so design details are important. HTP has some problems with heat exchangers in a new product several years ago and that soured a lot of installers, Be aware of that.

Can you get a PVC Vent pipe out the side of the house at your laundry for a condensing boiler? This is an important first step to in the decision. I’d seriously consider installing two Westinghouse water heaters if I had room. It may be less expensive than the Versa. The Versas eliminate a lot of problems associated with using a low mass boiler in an old system, especially and old high mass combi system like yours. They combine an indirect tank with a buffer tank for space heating into an element of the primary heat exchanger killing al lot of birds sight he same stone. It is a small footprint for a lot of stuff. (They make a Version for solar hot water use that adds a heat exchanger for solar hot water input too.) Lots of times, a buffer tank has to be installed to prevent short cycling, especially if there are a lot of small zones. A big problem is to be not oversized for small zones, but big enough to heat the entire house. Sometimes contractors actually combine zones that were introduced to save fuel after tthe 70s fuel crunch. They are difficult for a low mass boiler, even a combi boiler sometimes, to deal with.

The fin-tube cnvectors can be a problem with condensing boilers killing efficiency at very low winter temperatures, but in milder winter temps, you may get enough condensing operation to make it worth it. They dont put out a lot of heat at low water temps. If your house has greatly upgraded insulation and other weatherization, and stlll has all of its original convectors, it helps a lot.

I too think that a 100K boiler is way to big for your situation even if that is input rating from a relatively low efficiency boiler. My dad’s home in a much colder part of the State (Chenango) has a heat loss of less than half of that. Note that the capacity of the Versa is huge, but the equally huge buffer tank may fix that. A lower demand makes the water heater an attractive alternative.

Does the laundry room share a wall with the garage? Perhaps you can bump out the wall and build a closed size big enough to hold a 50 gallon hot water heater. If you do that then you could get have a free standing hot water heater of your choice and avoid the boiler combination dilemma.

I am a homeowner. The older low efficiency boilers are relatively simple but the high efficiency ones are somewhat complicated with the electronic gas valves etc. I would go with Viessman if you can afford it and have a good dealer nearby. DO NOT let the dealer sell you a wall mounted unit which is a glorified tankless water heater...get a real boiler with a lot of mass and an indirect tank for your hot water. The high mass boiler will retain heat longer, while the wall mounted units will constantly have to fire on and off...guess which one is more reliable.

The Versa-hydro appears to be the version that uses the secondary HX for space heat taking DHW direct from the tank/primary HX. I guess no one needs 180F water for space heat anymore.

Of the two, I can't really say what is a better fit. I don't know what your smallest zone is in terms of heat loss/emitter capacity nor your total heat need. The HTP will be more tolerant of oversizing due to buffering. I think that it will require less work around the installation. It will also be more tolerant of ignorant design.

Good idea, mike_home.

Note that correlation between wall hung vs floor standing and high mass (CI) vs low mass boilers is not great. Obviously high mass is harder to hang on a wall, but there are many low mass boilers sitting on their legs on floors.

It is not clear to me that a high mass boiler firing up to supply hot water to an indirect tank only to cool off into the living space is a good way to run a home in the summer months. When I was looking at them, there was one wall-hung combi boiler that had a small, built in buffer tank to eliminate the cold water sandwich (maybe Navien). I think that there are other strategies as well.

Fort the more quantitative minds, this study is a little dated, but illustrates the tradeoffs between some different approaches. Buildingscience,com might be another place to find objective information:

Optimizing Hydronic System Performance in Residential Applications

L. Arena and O. Faakye

Consortium for Advanced Residential Buildings

October 2013

The OP is located in Upstate or Western NY where the Winters are quite cold. The savings of using the indirect water heater in the winter will outweigh the cost of using it in the summer. The OPs main concern was reliability and not being without heat...a high mass boiler with indirect tank is a lot more reliable than using a combi boiler (aka tankless water heater).

“The savings of using the indirect water heater in the winter will outweigh the cost of using it in the summer. “

I’d be interested in seeing some numbers to support the projected cost savings. I’d also be very interested in seeing some cost of ownership/operating modern high mass boilers (including the on-off type rod modulating) vs. low mass (including combination and modulating) boilers.

The definition of “upstate” NY varies a great deal, usually depending on whether you are looking North or looking South from or at NYC. I don’t think, however, Long Island is thought of as upstate by the vast majority of people that like to debate this.

Although everyone wants reliablilty and it is high up on the scale, It looks like the OPs major problem is space.

The more I think about it, the more I think that one or two Westinghouse water heaters, if they fit, might be a bargain. If there was a breakdown, someone could quickly swap positions to provide heat and they are easily swapped out. The HTP Versa is a combination appliance, but of a very different type. It provides higher mass than any other comparable output boiler.. It has an exceptionally small footprint for what it does. I doubt that you could fit a boiler, low mass combi or not, and a buffer tank in the same space. Nor would a new boiler of any kind and an indirect tank fit in that space not even considering a buffer tank.

Another factor is combined cost of the boiler and installation. the latter is probably on the high end due to location. I look at tthe HTP as a way to shift away from those costs because few additional mods will be necessary*. My only question is reliability.

The OP has most of the summer to do research and make some informed decisions. The web sites I mentioned above used to be loaded with boiler people more informed than anyone that has posted here thus far.. In addition to those sources, some dealers with experience with the Versas and other modern boilers might be a good source, but you have to keep in mind their motives.

* OP, N.B., you will need to do something about your flue/chimmney. The demands for gas are different than for oil... If your chimney is completely enclosed by structure, you may be able to put a plastic line up the chimney for a condensing boiler. If the chimney is exposed, I have been led to believe that cannot be done. If you go non-condensing gas, the flue gas is still cooler than with oil. I believe that you need to reline the chimney with stainless steel flue. The other option with a condensing boiler would be to vent out the side. If you do that, you can scrap the chimney and reduce your roof penetrations the nest time you re-roof.

One suggestion I have is to find out how many boilers your installer is currently servicing, and what are the brands. I chose Buderus/Bosch boiler in 2012 and it seemed like a brand with good parts availability. However, the aquastat control unit started to get flaky this year (when it hit the high water temp cutoff), so I decided it should replaced. I then found out that Buderus and Honeywell had a falling out, so Honeywell no longer made the aquastat control unit for my boiler, and there was no Honeywell replacement cross-referenced. The only direct Honeywell replacement aquastat was from some guy in Florida who refurbishes them and resells them.

It took my repair guy about 3-4 days and two tries to get another brand of aquastat that had the right controls and sensor for my relatively simple non-condensing boiler, and several times he mentioned that "we don't have many folks with boilers anymore." My lesson learned is that maintenance and parts availability is very important for your primary heating system.

Bruce

I found this post quite useful, as I was shopping for a new boiler recently. I live in SEMass, so we do have relatively mild Winters. My home was all electric when purchased in 1986, however I converted to NG in 1989 after seeing some crazy heating bills. I installed a Weil Mclain HE-4 boiler, with a 30 gal Super Stor. The Weil Mclain is efficient, quiet, and economical, however would not fire on several occasions. In 2010, I installed the Gold update, with the UT 1013-200 control board. Finally, the boiler ceased to short-cycle, and runs right up to the limit before cutting out. The Friday before Memorial Day weekend, I began experiencing light-off issues, so I swapped in a spare ignitor, no dice. The brain box wouldn't prove the flame, and the gas valve would close after four seconds. I ended up removing the box, the control board, and cleaned it, and the Molex plugs with contact cleaner and it works fine. I'm ordering a spare box and ignitor to keep on the shelf. Parts support is good for these vintage boilers, and although there are nice rebates for a new high efficiency unit, I can heat my home for a decade on 10 grand..