Thoughts on replacing H2O heater with boiler...

david_21

I have heat pumps in my home with a propane H20 heater as the emergency backup, pumping hot water to heat exchangers in the AHU's. During cold weather, I change all the heat over to emergency, relying on the water heater to heat the house (more comfy and I believe less expensive in cold weather). The water heater is nearing the end of its life & I would like to replace with a boiler.

I your opinion(s), should I consider using a tankless water heater (Takagi, Bosch or similar) with a boiler that is operating seasonally? Or.... use the boiler year round for the domestic hot water?

I would prefer not to have a storage tank if possible, but it is not out of the question.

Any thoughts?

Regards and thanks,

David

david_21

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Constantin

Considering your fuel source...

... and intended use, I'd highly recommend a condensing gas boiler. Such a unit could probably halve your annual propane usage... Most water heaters have an AFUE around 60%, whereas a good condensing boiler will be in the 90%+ range most of the time.

Notable exceptions to the water heater efficiency lag are units like the AWH Polaris unit. However, the Polaris allegedly has had (historically) a number of design issues that don't lend it to low-temp usage (i.e. the tank has to be maintained at 140°F+ to prevent the ignitor from being destroyed by condensation from the tank). Plus, they're allegedly impossible to work on unless they're installed on a stand (everything is on the underside of the unit).

An IDWH is a good idea, BTW. It will allow you to install a smaller boiler that is better matched to the heating load rather than the potable-water recovery needs. Most homes these days have lower BTU needs for heating than what is needed to keep all the hot water outlets going at the same time. If the IDWH is properly constructed and insulated, it can be very efficient, long lived, etc. and when combined with a Thermostatic valve you can be sure that Legionella are killed and that you can stretch your hot water supply. Look into the HTP superstor series, for well-constructed yet reasonably-priced examples.

So, I'd take a closer look at a small Trinity, Munchkin, or the like to meet your hot water needs. Combined with intelligent control systems, any condensing boiler should reward you with a long life and a high efficiency.

DaveGateway

A combo wall hung

like the Baxi Luna might be an option if you don't use a lot of domestic HW. But if you have multiple bathrooms and like long showers, you need something with a tank. Maybe look at some of the combo units from Triangle Tube. Small boilrs lke the munchkin can be mounted on a stand over a 30 gal. low boy indirect tank. This setup would take up no more space then your current HW heater.