ᐅ Which tankless water heater is suitable for the kitchen sink?

Since I want to avoid a circulation line and the heat pump is located quite far from the kitchen, I would like to use a tankless water heater for the sink.

What power rating should this have for a basic kitchen sink?
Are there any general considerations to keep in mind when choosing a tankless water heater?

The installation will take place directly below the kitchen in the basement, so the pipe length will be a maximum of 2m (6.5 feet).

LostWolf schrieb:

What power rating should this one have for a simple sink?

Do you really want to wash dishes?
Then either go with a boiler (under-sink storage heater – which has low power and keeps the tank warm) or a proper instantaneous water heater (e.g., 11–13 kW).

LostWolf schrieb:

Is there anything in general to watch out for with an instantaneous water heater?

Make sure to have the appropriate electrical wiring and circuit breaker installed by a qualified electrician. Possibly three-phase power.

LostWolf schrieb:

The installation will be directly under the kitchen in the basement, so the pipe run will be a maximum of 2 m (6.5 ft).

And how far is the heat pump’s storage tank? Would that not cause issues for the other consumers?
Also, why install it in the basement and not under the sink?

You are spending quite a bit of money for relatively little benefit if you don’t use the heat pump’s domestic hot water.

nordanney schrieb:

Are you seriously planning to wash dishes by hand?

Well, pots, pans, etc. are actually easier to wash by hand than putting them in the dishwasher.

nordanney schrieb:

Then either with a boiler ("under-sink storage tank" – which has low power and just keeps the tank warm) or a "proper" tankless water heater (e.g., 11–13 kW).

Isn’t 11 kW a bit oversized for a single tap point that is just a sink?

nordanney schrieb:

And how far is the distance from the heat pump’s storage tank? Is that not an issue for the other water outlets? And why place it in the basement and not under the sink?

The bathroom is right above the heat pump (heat pump in basement; bathroom on upper floor).
The guest toilet on the ground floor is in close proximity.

nordanney schrieb:

You’re spending quite a lot of money for relatively little benefit if you don’t use the heat pump’s hot water.

Then I would just have to wait a long time for the water to get warm for washing, and the maximum temperature is limited.
(I’ll calculate the pipe length later.)

LostWolf schrieb:

Isn't 11 kW a bit oversized for a single tap point that only serves a sink?

Do you want hot water? Then you won’t avoid it. All the "small" mini units only provide water for hand washing but not enough hot water.

LostWolf schrieb:

Then I would just have to wait a long time until the water is warm for washing up, and the maximum temperature is limited.

50°C (122°F) hot water should be enough.

I calculated the pipe length if I were to connect the kitchen sink to the heat pump. It would be about 11m (36 feet), which corresponds to approximately 1.2 liters (0.32 gallons) of water volume in a 16mm (0.63 inch) pipe.

Can any of you estimate how long it would take to get warm water here?

(The heat pump typically heats the domestic hot water up to a maximum of 45°C (113°F) during normal operation.)

LostWolf schrieb:

(where the heat pump heats domestic hot water up to a maximum of 45°C (113°F) under normal operation)

I wouldn’t use such a low temperature. Both in my case and for my tenant (two separate heat pumps), it’s set to 50°C (122°F). This also reduces issues with Legionella.

LostWolf schrieb:

It’s about 11 meters (36 feet), which corresponds to approximately 1.2 liters (0.32 gallons) of water volume in a 16 mm (0.63 inch) pipe.

Can any of you estimate how long it would take to get warm water here?

That depends on the water pressure and the actual flow rate. At 3.5 bar (51 psi) and a flow rate of, say, 6 liters per minute (1.6 gallons per minute), it’s about 12 seconds. At 4 bar (58 psi) and 10 liters per minute (2.6 gallons per minute), it’s only 7 seconds. I think the latter value could be realistic.