ᐅ Sizing of Hot Water Heater and Heating and Ventilation Systems—Is It Proper?

Created on: 11 Dec 2017 07:34
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mertmk3
Hello everyone,

We are about to finalize the contract for heating and sanitary installations with the following conditions:

- Single-family house
- 170 m² (1830 sq ft) heated living area
- Solid construction with brick/concrete
- Underfloor heating
- Partially basement
- 4 people

We have been offered an Alpha Innotec LWD 70 HTD heating system combined with a Zehnder ComfoAir Q350 ventilation unit. Overall, I am okay with the devices, but I have some questions I’d like to discuss with the heating installer. Beforehand, I wanted to gather some opinions:

1. There is a hot water storage tank with a net volume of 180 liters (47 gallons). Is this sufficient for 4 people? The heat pump provides 7.7 kW only for hot water production (no solar or other systems).
2. It is a combined unit: Are the full 7.7 kW power for hot water and underfloor heating used alternately or only partially, but at the same time?
3. Is the heating system adequately sized?
4. Is the ventilation system adequately sized?

I would appreciate any experiences (possibly also with these devices) and opinions to prepare for the discussion.

Best regards
blackm8812 Dec 2017 18:32
So, if two of us are living/showering, the 235 liters (62 gallons) should be sufficient. With temperatures between 45-47°C (113-117°F) and a flow rate of 6-9 liters per minute (1.6-2.4 gallons per minute), the tank capacity is adequate.
A
Alex85
12 Dec 2017 18:45
The normal shower temperature is 38 degrees Celsius (100°F). This means that if you store water at 45 degrees Celsius (113°F), it will be mixed down before use. With your 235-liter (62-gallon) tank, you can easily shower for half an hour without considering reheating the water.
blackm8812 Dec 2017 21:09
That's how it looks.
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mertmk3
13 Dec 2017 07:50
Thank you for your input, I will now use this to start a conversation with the heating engineer.