ᐅ Auxiliary heating for hot water in a secondary apartment

Created on: 28 Sep 2020 16:00
J
JfkJo87
J
JfkJo87
28 Sep 2020 16:00
Hello everyone,

we are about to complete our small basement granny flat.
There is no water recirculation system for the granny flat, which means the hot water delivery (especially after long periods of inactivity) takes almost 20 to 30 seconds.
The pipes are surface-mounted (i.e., accessible), so I am looking for a way to keep the water at a “comfortable” temperature (around 35-40°C (95-104°F)).
The pipe runs approximately 10 meters (33 feet) on the surface before splitting with a T-junction to the bathroom (additional 4 meters / 13 feet) and the kitchen (additional 3 meters / 10 feet). The 4 meters (13 feet) and 3 meters (10 feet) sections are no longer optimizable, but there is still a chance with the 10-meter (33 feet) section.

Are there any ideas for this? For example, trace heating.

Thank you and best regards
tomtom7928 Sep 2020 17:16
There are these mini instantaneous water heaters that we have installed all over the workplace. They don’t produce hot water, just lukewarm. But isn’t the pipe insulated?
B
BobRoss
28 Sep 2020 21:50
I would advise against using an electric trace heating system for the pipes, as there is a risk of unintended Legionella growth if the stagnant water is only kept lukewarm. This is especially true if some taps might not be used daily.

The simplest solution is the one recommended by tomtom79 – you need a so-called "solar-compatible" instantaneous water heater. Other options could be reducing the pipe diameter to decrease the volume of water in the pipes, combined with better thermal insulation, if these parameters can still be adjusted – but from your description, that does not seem likely.

The drinking water regulations require that the water volume in the hot water pipe between the heat source and the furthest tap does not exceed 3 liters (0.8 gallons). Otherwise, a circulation system must be installed or an annual inspection conducted (note: this is a simplified summary; it is best to review the full regulation).
K
knalltüte
29 Sep 2020 04:36
Especially for rarely used taps, installing a circulation system would be an extreme waste of energy! It’s good that there isn’t one! Trace heating or especially cooling (such as beer cooling) is used for beverage piping in the hospitality industry.

A small under-sink unit (or apartment station) would probably help. Legionella bacteria thrive at certain temperatures. Please take the contribution from @BobRoss seriously.