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domestic hot water storage

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DrAliG

Military
Jun 23, 2008
1
What are the most efficent settings to heat a domestic hot water storage tank, with an indirect gas boiler and immersion heater avaliable. Both winter and summer need to be considered ie winter time the bolier also heats the central heating system, but in summer only heats the storage tank.
 
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The most efficient, for a low duty cycle hot water system, is probably a tankless system. While the instantaneous BTUs are rather staggering, there is zero heat loss to worry about the rest of the time.

TTFN

FAQ731-376
 
It depends on what the hot water is for. If it is for showers and hand sinks, set it to no more than 110 DegF. If it is for kitchen use only (no contact with people), set it for 140 Deg.F Of course for dishwasher use, it will have to be boosted to 180 Deg.F for sanitizing.
As far as efficiency, be sure the water heater tank and hot water piping are well insulated. If you have long runs to a HW user, consider using a recirc pump. This avoids wasting water down the drain waiting for it to get hot.
 
The temperature setting is never quite that straightforward. Invariably, it will be a balance between safety and shower capacity. Safety drives the temp down towards 110ºF, while simultaneous shower capacity might push it up to 140ºF, particularly if the tank is relatively small. Additional factor is whether there people whose reaction times are slow, which drives the temperature down.

TTFN

FAQ731-376
 
Instantaneous heater standby loss is low; second law of thermo predicts there will be heat loss.
 
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