Hello.
I am planning to install a Vaillant ground source heat pump VWF 88/4.
We are considering installing a second electricity meter to benefit from a cheaper tariff for the heat pump.
However, this meter would be off for up to 6 hours per day.
As far as I know, we do not have a buffer tank integrated.
Alternatively, we could use the regular electricity supply (one meter). Overall, this would cost about €250-300 per year more than with the heat pump tariff.
I am concerned that during the off periods, the electric heating element might turn on, and we could end up spending much more than the €250-300 savings.
How does the electric heating element usually work – does it only activate in emergencies, or does it always come on when hot water is drawn?
I would appreciate any answers or experiences.
I am planning to install a Vaillant ground source heat pump VWF 88/4.
We are considering installing a second electricity meter to benefit from a cheaper tariff for the heat pump.
However, this meter would be off for up to 6 hours per day.
As far as I know, we do not have a buffer tank integrated.
Alternatively, we could use the regular electricity supply (one meter). Overall, this would cost about €250-300 per year more than with the heat pump tariff.
I am concerned that during the off periods, the electric heating element might turn on, and we could end up spending much more than the €250-300 savings.
How does the electric heating element usually work – does it only activate in emergencies, or does it always come on when hot water is drawn?
I would appreciate any answers or experiences.
Is the power really being cut off? As far as I know, there is a contactor in the heat pump that needs to be connected separately, and the signal from the energy supplier is sent through it. So, the heat pump should still be turned on (turning off the heat pump every day isn’t good for it), but it simply won’t be able to heat.
The electric heating element could theoretically be connected to another meter and powered with household electricity; usually, there is only one control signal from the heat pump, but it receives power directly from the distribution board.
By the way: in our case, the savings for 3000 kWh (about 10,200,000 BTU) annually for the heat pump would have been just 2-3€ per month. We would never have recovered the extra effort from that...
The electric heating element could theoretically be connected to another meter and powered with household electricity; usually, there is only one control signal from the heat pump, but it receives power directly from the distribution board.
By the way: in our case, the savings for 3000 kWh (about 10,200,000 BTU) annually for the heat pump would have been just 2-3€ per month. We would never have recovered the extra effort from that...
@Jochen
Of course, nothing works during the blackout period. I meant that because of the blackout, the water storage tank or the underfloor heating cools down, and after the blackout period, the heating element then steps in to quickly reheat everything (for example, when it’s -20°C (–4°F) outside).
@toxicmolotow
New build with 42.5cm (17 inches) Poroton block walls, KfW 55 standard, 240m² (2,583 ft²) heated floor area. Where can I find the energy demand? Is it stated in the energy performance certificate (EPC) / thermal insulation certificate?
The 8000 heating watts per year are just my estimate.
Of course, nothing works during the blackout period. I meant that because of the blackout, the water storage tank or the underfloor heating cools down, and after the blackout period, the heating element then steps in to quickly reheat everything (for example, when it’s -20°C (–4°F) outside).
@toxicmolotow
New build with 42.5cm (17 inches) Poroton block walls, KfW 55 standard, 240m² (2,583 ft²) heated floor area. Where can I find the energy demand? Is it stated in the energy performance certificate (EPC) / thermal insulation certificate?
The 8000 heating watts per year are just my estimate.
T
toxicmolotof12 Aug 2016 09:06Do you already have an energy performance certificate or a heating load calculation?
The walls and the KfW standard only help to a limited extent, as it depends heavily on the building design.
However, the estimated energy demand seems too high to me.
For comparison:
125m² (1345 sq ft), KfW 55 (energetically rather poor building design).... 2000 kWh heating, 1000 kWh domestic hot water (3 people).
I would have guessed a maximum of 5000 kWh based on the information given and a southwest-facing heat pump.... (layperson!)
The walls and the KfW standard only help to a limited extent, as it depends heavily on the building design.
However, the estimated energy demand seems too high to me.
For comparison:
125m² (1345 sq ft), KfW 55 (energetically rather poor building design).... 2000 kWh heating, 1000 kWh domestic hot water (3 people).
I would have guessed a maximum of 5000 kWh based on the information given and a southwest-facing heat pump.... (layperson!)
cumpa schrieb:
I meant that during the lockout period, the water storage tank or underfloor heating cools down, and then after the lockout period, the heating element steps in to quickly reheat everything (for example, when it’s -20°C (-4°F) outside). It probably won’t cool down that much. That’s why, as @toxicmolotow suggested, you should take the lockout periods into account when designing the heating system. Also, think carefully about how often we’ve actually had -20°C (-4°F) recently.
cumpa schrieb:
die 8000hw/Jahrsind von mir nur geschätzt Is that 8000 kWh per year only for heating and hot water? That seems a bit high. Did you take the heating demand value directly from the heat load calculation? If so, you still need to divide that by the expected COP of the heat pump to get the actual electricity consumption of the heat pump. You can usually expect a COP factor of around 3, depending on the air-to-water heat pump.
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