ᐅ Sizing of Hot Water Heater and Heating and Ventilation Systems—Is It Proper?
Created on: 11 Dec 2017 07:34
M
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
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
Domski schrieb:
Yes, combination units are designed precisely for about 75 to 80% of average families. They usually fit well, and especially prefabricated house manufacturers don’t have to put any effort into the system design. The underfloor heating manufacturer handles the sizing, which determines the heating load, then you pick the next larger combination unit with or without ventilation next to it, and the manufacturer takes care of the commissioning. That’s it. But if you have specific requirements or deviate from the standard, it often becomes difficult. And for some, just having three kids is already too much 😉No problem in that regard, we are building a custom design with an architect, and this was just the heating installer’s first proposal. That’s why I want to discuss the topic thoroughly with him, but at least I want to have a basic understanding of it beforehand.
Alex85 schrieb:
The size of a combination unit is simply limited. You can’t fit more water in the available space. An external storage tank is not that much more expensive. You need to have the space for it, but a system with a small tank also has clear advantages because it can be recharged much faster and delivers “bath temperature” water.So you would rather stick with the small storage tank?
blackm88 schrieb:
We also have a combination unit with 8.4 kW capacity and controlled residential ventilation with heat recovery. Our hot water tank has 235 l (62 gallons), I think that fits well. For most units, domestic hot water preparation takes priority.Is the 8.4 kW heating capacity rated at A7 or A2? Have you already put the unit into operation? How many people live there, and what kind of water consumption do you have?
I would only choose a larger storage tank if there is a particularly high demand for hot water or if, for example, there is space for a separate tank in the basement anyway. If it ever needs to be replaced, that is definitely easier than repairing or replacing a combination unit.
mertmk3 schrieb:
Is the 8.4 kW heating capacity at A7 or A2 conditions? Have you already put the unit into operation? How many people, and what are the water usage patterns? Heating capacity at A-7/W35 (EN 14511): 8.34 kW (29,000 BTU/h)
Heating capacity at A2/W35 (EN 14511): 5.16 kW (17,600 BTU/h)
Heating capacity at A7/W35 (EN 14511): 4.40 kW (15,000 BTU/h)
More details in the datasheet
The unit has been installed in the house since March, then the screed drying phase, etc., moving in on 10.08., commissioning on 11.08.
Currently, there are still 2 people living, approximately 165 m2 (1,775 sq ft) of living space
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