Heat Pumps and Con men

[ericmark]

My father-in-law was having a salesmen around to sell him a new government backed system which takes the energy from outside and puts in into the home meaning as the sales man said you pay nearly nothing for gas and electricity the electric is just for a pump and the gas is retained as it will not work if the outside temperature goes below minus 15 degs C.

So he passed me the two bits of paper in his hand. It said output around 5kW input around 1.7kW can't remember exact figures but clearly it still uses a far bit of power. He was saying no more than £100 annual bill for electric which just did not seem to compute with any of the info on paper.

It was Hitachi and the top of the list of options said model 42P so on returning home went onto the internet.

As far as I can tell it was This system called Eco Cute and it would seem this would save money where there is no natural gas supply but although reducing a all electric heating bill to 1/3 compared with electric fires it clearly is not all your heating and hot water for nothing bar for when you first start it up and for a small pump.

As to if the Polish guy believed what he was saying I don't know but when I said I was an electrical engineer he could not leave fast enough.

However it was a very convincing patter and I wonder if my 86 year old father-in-law would have been taken in if I was not there?

I think the salesmen drive around and see the water solar panels on the roof and say "Oh there is another sucker can we sell him our stuff"?

Best of it just 10 miles up the road there is no natural gas and even without all the lies the system would make sense.

These salesmen seem to just move from one scam to next with perpetual motion. Has anyone else had one of these guys around.

Eric

 

[stem]

Some of that is correct. Air source heat pumps claim up to 300% efficiency but only under perfect conditions. Their efficiency falls off as the air outside cools. So the colder it gets outside, the more the consumption increases.

I have it (Mitsubishi) in my new build, no gas supply, office which has won awards for its environmental friendlyness, but I have to leave it on 24 hours a day now it's below freezing to maintain 21 degrees inside (Uses 7 hours of off peak rate at night) At the moment because the indoor unit is producing heat, the outdoor unit gets even colder than ambient, so it is continually icing up. Sometimes 30 minutes of every hour it spends defrosting itself, which means no heat whatsoever is provided inside the building and it continues to consume power.

A positive is that it can work in reverse and cool in the summer (should we have a warm enough summer to need it.)

One shortfall with heat pumps is that they can't produce the temperatures boilers do, so normal radiators would only get tepid. They are usually linked up to underfloor heating pipes, or just blow out warm air into the room from an indoor unit, which can be bulky and slightly noisy. Either way, it's a major undertaking if you want to install one to heat an entire house.

Ground source heat pumps fare better in terms of efficiency than air source, because whilst the air is below freezing, the ground can still be quite a few degrees above.

Mine's not cheap to run, I would guess that if you estimate the KW's necessary using traditional electric heating, you may save a third of the electricity by using a heat pump. However the cost of buying and maintaining one will wipe out a few years of savings.

I reckon air source heat pumps would be great in warmer European countries, or the southern USA where it never drops below 10 degrees, but not for good ol Blighty.

Regarding cost maybe £100 per month is more likely, but a 5 kW (maximum rated output) unit would only be good enough for one room. Because it wouldn't be producing 5 kW of heat today. (If you are reading this post in the future (wow a time machine) it's -5 degrees here today)

 

[ericmark]

Interesting may years ago (1980's) we had them in the Atlas mountains of Algeria some air conditioner using reverse the pump method to heat. Others had pain element. It was on a pipe line job from Sahara to Coast and freezing up of core was a problem in some areas. It was this recall which had given me the knowledge to realise it would not work as the salesman described.

I would have thought before fitting complex heating systems a heat recovery system would be required first looked at them a few times but can't see with my house where it would fit.

 

[stem]

I've just read the Eco Cute link you posted. Interestingly it makes mention of heating water up to 90 degrees using a heat pump, and even boiling it. That's the first time I've seen figures like that quoted. However it only seems to be for hot water, so perhaps it can produce the temperature but not the volume for heating.

 

[bernardgreen]

The "on commission" salesmen will show figures of high efficiency without relating them to the conditions needed to achieve those high levels of efficiency.

The basic law is " the higher the difference between source temperature and destination temperature the lower the efficiency "

Interestingly it makes mention of heating water up to 90 degrees using a heat pump

Definately possible but efficiency would be low and it probably disn't mention how long it would take to bring a pint of water up to 90 degree C

EDIT with changed to without

 

[ricicle]

"Up to 300% efficient"

This is based on the electricity used by the pumps.
Gas is approximately 1/3 price of electricity so do the maths and decide if you want the hassle.

 

[ban-all-sheds]

If you are reading this post in the future (wow a time machine)

I have a time machine.

It goes at a rate of 60 minutes per hour (although I'm sure it slows down in meetings sometimes).

No reverse gear though.