Should my indirect hot water heater have a mixing valve?
I have a 2300 square foot colonial, built 1960 in Massachusetts (Zone 5A), with three zones of fin tube baseboard. There’s a 75 gallon whirlpool tub which we almost never use; the two showers are fairly low-flow. Heat loss done by Comfort-Calc.net was 55,840. I use town water, which is very good quality (Quabbin reservoir). I’ve accepted a bid to replace my heating system with a Lochinvar WHN-85 boiler and SIT40 indirect water heater.
The plumber is recommending against using a mixing valve on the SIT40 output due to reliability concerns (e.g. scaling). But, I’m concerned about Legionella (although I’ve never had a mixing valve before, and have never heard of local problems), and would like the flexibility of being able to raise the storage tank temperature.
Any thoughts on this? If I do ask for a mixing valve, the plumber won’t have a lot of experience with installing one; any specific valve recommendations?
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