Burnham RS-109 DHW coil scaled. Searching options for replacement (all or DHW only)

[Casa14]

House built in 1990, 1100 sq ft, 500 finished basement located in seacoast NH (heating 99% is 9). House is well insulated, not drafty at all. Basement was an upgrade done 10 years ago by previous owners and it is cold, even though it has a baseboard (too small for the space).

Current boiler is the RS-109, original to the house, that supplies heat via baseboards and domestic hot water. The DHW coil is scaled and thus not heating, only warming the water. Since the boiler is also 26+ years old (and is OK for now), we are debating options for the future in the heating and for the present with the hot water issue. We have no natural gas, so we are limited to oil, changing over to propane which is expensive, or getting mini splits.

Reading here, I see many people against the tankless coil in the boiler, but other people recommend them, so we don't know which way to go. Is it worth replacing it or going with another system altogether? We have the space to put in an electric WH, either regular or heat pump (which is another controversy since some people recommend the Heat Pumps while others consider they don't work well up north).

Thanks!

 

[Jac04]

For your present issue, have you considered just having the DHW coil cleaned?

 

[Sponsor]

 

[Dana]

Got a K-factor on wintertime oil-fill up, so we can estimate the heat load?

How many running feet of baseboard? (Broken down by zones, if there is more than a single zone.)

Odds are the whole-house heat load is somewhere between 13,000 - 18,000 BTU/hr @ 9F, which makes the RS-109 about 5x oversized for the 99% load, and probably insanely oversized for the radiation. If they over-sized the radiation to limit the short-cycling you can probably heat the place with water much cooler than 180F.

If you have enough baseboard to heat with 140F-150F water you'll probably do better with an oil-fired hot water heater set up as a combi-heater than with another ridiculously oversized boiler, and it would deliver a LARGE improvement on the hot water performance, with much lower standby losses. With a hot water heater the thermal mass of the tank limits the short-cycling, no matter how small the zone radiation, or the number of zones.