Not Sure What to do

[mjohnson267]

I'm finally getting a gas line installed from the main to my house. We're having the oil tank, water heater, and the ancient boiler removed.

I'm looking to buy a new gas boiler to heat the home. I'm not sure if I should look at the combi units or get a separate gas boiler and gas water heater. We live in the North East and have a 2000 sq ft home.

The local gas company is offering the following rebates:

Hot water boiler AFUE 96% - $1,500
Hot water boiler AFUE 90% - $1,000
Hot water boiler AFUE 85% - $500

Combined High-efficiency boiler & water heating unit: Condensing Boiler with on-demand domestic hot water minimum AFUE Rating of 90% - $1,600

High-efficiency indirect water heater - $400

Condensing Gas Water Heater - $500

High-efficiency on demand tankless water heater $800

Should I get the combi and if yes, which brand? Or should I get separate units? I can't seem to find recommendations or ratings for gas boilers. Any help would be appreciated. Thank you

[Wheelbaron]

OK first the question of combi or separate units. Personally I am a fan of indirect tank type domestic water heaters. The reasons are that you get the same great efficiency as the boiler provides, the boiler gets used throughout the year, so it is not sitting static all summer, and the indirect tank is easy to service and maintain, where the combi unit is much smaller and saves space, but harder to service.
As for brand, you need to ask your HVAC contractor what they recommend, most contractors are going to recommend a brand that is locally available, with good access to parts. I use several brands here, depending on what features I need for the install. Do I want a SS or aluminum heat exchanger, do I want an integrated pump or external, there are a lot of control options, it all depends on the individual lay out.
As for type of boiler, again it depends on several factors. High efficiency boilers are great, but require good maintenance. Cast iron boilers require less maintenance, and last a long time, but venting and efficiency are an issue. Often I can install a high efficiency boiler for close to the same $ after rebates and tax credits because of things like venting, and stairs that may have to be braced or removed to bring the new boiler into the home. My advice is look for good local contractors and find one that you are comfortable with.
There is a good post in the residential forum on how to pick a contractor. If you are asking for DIY then please read the rules at the top of this forum.

[MM#7]

OK first the question of combi or separate units. Personally I am a fan of indirect tank type domestic water heaters. The reasons are that you get the same great efficiency as the boiler provides, the boiler gets used throughout the year, so it is not sitting static all summer, and the indirect tank is easy to service and maintain, where the combi unit is much smaller and saves space, but harder to service.
As for brand, you need to ask your HVAC contractor what they recommend, most contractors are going to recommend a brand that is locally available, with good access to parts. I use several brands here, depending on what features I need for the install. Do I want a SS or aluminum heat exchanger, do I want an integrated pump or external, there are a lot of control options, it all depends on the individual lay out.
As for type of boiler, again it depends on several factors. High efficiency boilers are great, but require good maintenance. Cast iron boilers require less maintenance, and last a long time, but venting and efficiency are an issue. Often I can install a high efficiency boiler for close to the same $ after rebates and tax credits because of things like venting, and stairs that may have to be braced or removed to bring the new boiler into the home. My advice is look for good local contractors and find one that you are comfortable with.
There is a good post in the residential forum on how to pick a contractor. If you are asking for DIY then please read the rules at the top of this forum.

well said!

[skippedover]

I'm finally getting a gas line installed from the main to my house. We're having the oil tank, water heater, and the ancient boiler removed.

I'm looking to buy a new gas boiler to heat the home. I'm not sure if I should look at the combi units or get a separate gas boiler and gas water heater. We live in the North East and have a 2000 sq ft home.

The local gas company is offering the following rebates:

Hot water boiler AFUE 96% - $1,500

The gas company offers the rebates but don't expect to get 96% actual efficiency unless your system is masonry radiant floors or snow melt. Higher temperature applications will reduce the AFUE several per centage points. Just FYI.

Hot water boiler AFUE 90% - $1,000
Hot water boiler AFUE 85% - $500

Personally, I'd recommend skipping the intermediate models and go for a high efficiency model. The reason I say that is because all of them have the same basic mechanical issues, those being inducer motors, control boards and thermistors. Since they all have those, why not realize the maximum efficiency you can?

Combined High-efficiency boiler & water heating unit: Condensing Boiler with on-demand domestic hot water minimum AFUE Rating of 90% - $1,600

The combination units are my preference as you get more 'bang for the bux' but understand, the life of the system is 15-18-years. It's going to cost a lot to have the water piping reconfigured for the new boiler application but once that's accomplished a replacement unit should cost significantly less. That said, I have two preferences on boilers. One is due to our long history of trouble free installations and nearly zero problems. The other is due to the companies reputation and their highly competetive price. (Keep in mind, you get for what you pay, no more!) The former is the Triangle Tube and the latter is the Navien Combi boiler. Please note that a full load analysis should be performed on the home before any job is quoted or any quote is accepted. The TT combi boiler is available in one size only. So sizing by load analysis is a must.

High-efficiency indirect water heater - $400

Condensing Gas Water Heater - $500

High-efficiency on demand tankless water heater $800

These are over rated and under performing. By that I mean that the average household spends about $120 per year to enjoy hot water when heating it by gas, using a conventional atmospheric gas water heater. At the purchase price of a tankless, you'd have to be using it in a car wash to realize the financial benefit. So unless your home is unoccupied for lengthy periods (days, weeks or months) when no-one would be using any hot water at all, then I'd recommend against a tankless.

Should I get the combi and if yes, which brand? Or should I get separate units? I can't seem to find recommendations or ratings for gas boilers. Any help would be appreciated. Thank you

Again, sizing is very important. Some manufacturer's have combi boilers that reach very high Btu requirements while others limit the size of the combi boilers. If you want a particular manufacturer of boiler (I do like the Triangle Tube personally in our area) and they don't make a combi in the size you need, then doing the boiler with an indirect water heater is my suggested solution. FWIW, I'm not a fan of aluminum block boilers. There have been some issues with some of them and I'm just not ready to embrace acidic condensate and aluminum. I prefer the stainless steel boilers. JMO.

[firecontrol]

To the HO, what you didn't post was the most important information that should be taken into consideration when choosing a new heating and water heating system.
1) What kind of radiation does the home have? Is it radiant, large cast iron radiators, fin tube, cast iron baseboard?
2) Is the heating system zoned with multiple thermostats or just one?
3) How do the occupants of the home use hot water? How many people in the home and how often to multiple people need or want to use hot water at the same time?

I can't stress enough that to try and make a unit fit into your unique situation simply because of the highest rebate amount will lead to a multitude of problems, could make the system hard to live with and almost always leads to very expensive repairs and maintenance costs and a short life of the equipment. It's like trying to pound a square peg into a round hole.

Also when replacing your base equipment/boiler is the time to think about the potential upgrades like zoning. To do this afterwards could mean that the boiler you picked is the wrong size. You have time to educate yourself and make an informed decision.

[2old2rock]

Navien Combi-gas is a very nice unit - worth looking into.

[mjohnson267]

Thanks for all the replies. Here is some more info:

House has fin tube radiation

4 zones all with separate thermostats

House is around 2800 sq ft. (800 in finished basement, 1000 on 1st and 1000 on 2nd floor)

There are 4 people in the adults with no more than 2 showers going at the same time.

Thanks for any info you provide.