Oil to Gas Conversion: Combination Boiler vs Traditional Separate Water Heater

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valethor

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Long Island, NY
Hi -
I am on Long Island, NY. I am converting my house from oil heat to gas heat and I am hearing different things from the different companies I am quoting regarding whether I should do a combination boiler/hot water tankless unit or a traditional boiler + water heater. I trust this forum (where no one has a monetary incentive to give me advice) so I'm hoping to hear your opinions.

My house is about 3000 square feet. We have four full bathrooms, but right now it's just my wife, myself, and our 18 month old.

I understand there are three options:
Direct water heater + boiler
Indirect water heater + boiler
Combination tankless unit

One plumber is suggesting the indirect option and says the tankless are much more difficult to service, require annual maintenance, and availability of parts can sometimes be an issue. He also said in the winter time the water can take forever to heat up, we won't have hot water when the electric is out, and we can't run a shower at the same time as a dishwasher or laundry. The other plumber is suggesting that the combination tankless unit is the way to go and sells the "infinite water" pitch to me. He said if money is no object he always recommends tankless.

Assuming that the size that the equipment takes up is not an issue (my basement has a large unfinished boiler room), what setup do you guys recommend?
 
I’m with plumber number one until he says you can’t run more than one fixture at a time with a tankless That’s only true if it’s not sized properly.

Tankless is great if you want infinite water. That’s true. In fact that’s the only reason I would sell a tankless, right now., that may change one day.
 
Hello from suffolk.
Im a fan of indirect heaters, But that depends on your boiler size, The one plumber was right about all the parts, with a indirect its just a aquastat and circulater.
Im not to familiar with tankless but people either love them or hate them hear, do you have the room/ability to vent one.
 
Single-point tankless tends to work best in smaller or zoned houses. One unit ought to service typical use for under ~2000²'. Over that size two or more zones would be good: separate tankless heaters or sole point of use systems (POU), probably electric if the utility is affordable, natural gas if they can be vented.

Also possible to use one of the systems you mention as the primary that feeds point of use systems with partly heated (tempered, say to 70°), then use electric units, which are inexpensive to purchase and relatively simple to install, for each hot water POU, brought up to desired temperature. There is a premium for installation, but if utility, especially electric costs are high and you have good access for the separate installations, this hybrid could save money in the long haul. One key is that with tempered hot water supply, the POU tankless heaters are sized smaller and use much less energy to satisfy demands.
 

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