News "costly mistake" by prioritising high-tech heat pumps over basic insulation. Really?

[ericmark]

Yes, OK, stop losses first, or at the same time, but if the heat pump does not work with poorly insulated homes, neither will it work with well insulated homes.

Yes, I see we have a 60 amp fuse in the supply to many homes, so 40 amps for the house we have 20 amps for the heat pump, so 4.6 kW they can be 400% efficient it seems, so 18.4 kW into the home, so if the home had a 25 kW gas boiler, then either the boiler was well oversized to start with, or a heat pump is not going to work.

I have not got a gas smart meter, but would think it is similar to electric, so this shows me what I am using with electric if there is something similar for gas, then it should be easy to see how much any house needs if using gas, oil not so easy, I used around 1200 litres a year, well none in the summer, so that's around 12,000 kWh divided by 182 days so around 65 kWh per day, so around 12 amps average, (at 400% 3 amps) so it is clear likely for me the heat pump could produce enough. Supported by during the coldest days, the 20 kW boiler has coped.

But working out how much power an existing home needs, should be easy, we have records to work with. New home OK, we don't know what the losses will be, but will an existing home, if it needs a 35 kW gas boiler, then it needs a 9 kW heat pump if working at 400% or 38 amps, clearly you can't run a house on 20 amps, so the 60 amp fuse would need up rating to at least 100 amps.

The only way a heat pump can fail is if it's not 400% efficient. Or if it can't deliver the output due to the evaporator freezing up, so heat pumps should work if outside above 10°C or lower than zero only if outside is between 0 and 10°C do we have a problem. At 0 to 10°C there is a high possibility of condensate freezing, below zero and very little humidity in the air, so very little condensate, so very little to freeze. And above 10°C also unlikely the condensate will freeze.

So unless the winters in the UK are between zero and 10°C heat pumps should be fine. Can anyone see the flaw with heat pumps? I do not think down to not enough insulation on the home.

I am sure a heat pump powered by a 28 sec gas oil engine will work fine, the main problem is trying to use an electric motor. I think it would be a Sterling idea, pun intended.

 

[Harry Bloomfield]

I have not got a gas smart meter, but would think it is similar to electric, so this

The big difference, is the granularity of the data for gas. Electric, is able to generate regular, 10 second readings. Gas is limited to a reading every 30 minutes.

 

[ericmark]

The big difference, is the granularity of the data for gas. Electric, is able to generate regular, 10 second readings. Gas is limited to a reading every 30 minutes.

The chart I show is every 30 minutes.

I am sure, there is enough data to say if using x kWh of gas or oil per year, it needs a heat pump of y kWh output. What it with meters pointed at a wall or window. 95% of the time, you can look at the bill for the previous year. OK, some people cook with gas, but if they need gas for cooking, so still need to pay standing charge and keep gas meter, they why fit a heat pump?

 

[drives]

I think you are confusing kwh input of the ashp with the output? A 9kW heat pump isn't equivalent to a 35kW boiler. Both figures relate to the heat output. 9kW is still plenty for most homes and certainly assuming you are referring to heat only/system boilers, a 35, 25, or indeed 20kW boiler will be significantly over sized for most homes.

Another thing to be mindful of is that the parameters used to give this rating varies across manufacturers. A 12kW badged ashp may in fact only be capable of 10kw heat output at -2. Another manufacturers unit, badged as a 12kW, may in fact have a 12kW heat output at -2. It doesn't necessarily mean one ashp is better than the other and/or any more efficient. It just needs to be taken into account when sizing.

The biggest issue is that the BTU of emitters will fall significantly at the lower flow temps that are required for ashps. Thus, these need to be sized appropriately. If they can be (which in most homes again they can be upgraded without it looking like a radiator showroom), it is indeed a misnomer that ashps will only work effectively in highly insulated properties.

The first thing we did when embarking on our installation was use a rule of thumb calculation to give us an indication as to what size ashp we required, based upon previous gas usage. This proved quite accurate. Not a bad thing to slightly oversize taking into account DHW runs and defrost cycles.