UPDATED: Air Source Heat Pumps/Air Con - Full Info & Guide, is it cheaper to run than mains gas?

Ecodave

Hi Graham,

The CoP of a condensing gas boiler is about .9 as they tend to be about 90% efficient. So an alternative gas powered machine with a CoP of 1.3 would be about a third cheaper to run. Your maths only work out if you are considering a fuel (electricity) that is 3 times the price of gas.

The machine that was being described would directly replace a traditional gas boiler. So would heat water to power radiators. The presenter stated that whilst production of these units is a few years off (think he said 2017) he thought that the extra cost of these units in comparison to a modern combi boiler would be paid off through savings within 3 years. I am guessing from this that the extra cost would be about £1000. Obviously, some guess work is involved in these figures as 2017 is some way off, but interesting stuff.

John_Pierpoint

Hi Dave,
I was at the same presentation given in front of the "crescent" of traditional hard to heat homes. It is a small world

The guy from Ulster had investigated two "air source" heat pump enhanced technologies - perhaps because natural gas over there tends to come in bottles.:D

The improvement he had identified was the same principle as used by "gas fridges" (I had a second hand one of those in the summer of love 1967. It was given to me to help furnish a £4k two bedroom flat).
Apparently they are still used for caravans, where a large battery and powerful inverter might not be available to those wild camping.

I don't understand the principles but they sound similar to "thermodynamic panels".
Here is a nice cynical thread on the whole subject; it helps cut through the "biillsh1t baffles brains" marketing hype.

http://www.diynot.com/forums/viewtopic.php?t=224641&start=30

Obviously Prof Neil Hewitt of Ulster University knows that the idea of putting the "heat pump onto the exhaust of a condensing boiler" could be worth £ millions.
In theory there are two possibilities of making gains that ordinary air source heat pumps cannot achieve: getting the latent heat out of the vapour that has escaped the boilers condenser (ever had a "condensing" clothes dryer- they don't do a good job) by dropping a pile of ice on the lawn. The exhaust gas is hotter than the outside air and in theory has had most of the water removed already, leaving just the CO2. It won't coat the pump in ice, as it is launched at a below freezing temperature into the garden.
However he did admit that in a "zombie" Britain, run by bean counters, the Germans or perhaps the Italians might get the prime mover advantage.

You could try a PM to "cardew" - if I remember correctly he has a heat pump on the output of his clothes drier.

How long before we get a retrofit to an existing gas boiler and the exhaust now drops down the outside of the building in a shower of "snow" and enters the downstairs window of a fresh air fiend pensioner and the CO kills her?

Cardew

John_Pierpoint wrote: »

You could try a PM to "cardew" - if I remember correctly he has a heat pump on the output of his clothes drier.

This is the machine I have.

http://www.miele.co.uk/Products/heat-pump-tumble-dryer.aspx

Ecodave

Blimey Cardew, that must have cost a pretty penny! I was looking at tumble dryers a month or so ago and the B rated ones were eye-wateringly expensive.

John - thanks for the feedback. I would have thought there would be more to it than just the sort of shady info related to thermodynamic panels, I may be wrong.

Ps gas fridges and the summer of love = showing your age.;)

richardc1983

There is another cheaper heat pump dryer from beko that I paid £315 they have gone back upto £325 now but pretty often they sell them for £315. A load costs 12p to dry and because it drys the clothes at about 45c heat rather than 90c anything can go in it. An 8kg load dries in about 2.5 hours... Not much higher than a normal heating element dryer.

http://www.ultimate-appliances.co.uk/beko-dpu8360w-heat-pump-condenser-tumble-dryer.html

John_Pierpoint

Ecodave wrote: »

Ps gas fridges and the summer of love = showing your age.;)

No it is wisdom

Anyone got mean time to failure figures on these:
http://www.ultimate-appliances.co.uk/beko-dpu8360w-heat-pump-condenser-tumble-dryer.html
http://www.miele.co.uk/Products/heat-pump-tumble-dryer.aspx

The Germans have a figure of 21.5 years for ground source heat pumps.

My original dryer a Hotpoint lasted about 20 years, but in that time got through several drive belts, two sets of PTFE bearing pads, the bearing plate needed drilling and pop riveting when its spot welds failed and finally the front baffle plate wore through.

richardc1983

I am unsure but the only difference is a compressor to produce the heat the rest of the workings are the same and as it doesn't get upto as high a temperatures as a normal dryer would this must cause less heat stress on other components.

John_Pierpoint

I suppose that the heat pump also acts as a dehumidifier ?!? Where does the water go? Is it plumbed in or does one clean the lint filter and then tip out a litre of water too ?

Cardew

John_Pierpoint wrote: »

I suppose that the heat pump also acts as a dehumidifier ?!? Where does the water go? Is it plumbed in or does one clean the lint filter and then tip out a litre of water too ?

Like most condenser dryers, mine can be plumbed in or there is a container to hold water that needs to be emptied every one or two loads - takes two seconds.

grahamc2003

John_Pierpoint wrote: »

I suppose that the heat pump also acts as a dehumidifier ?!? Where does the water go? Is it plumbed in or does one clean the lint filter and then tip out a litre of water too ?

Ours is an AAA rated Hotpoint Ultima something or other, and yes, we have to empty a litre or two out everyday, takes no time at all. The water container comes from the top of the machine, a big improvement from our previous one where you had to get on your knees to get at the water container. I was amazed that mine only uses 1.25kWh for a full load, so costs about 8p on e7. I've always wondered how it did it for that little electricity, I'm now beginning to wonder whether there's a heat pump in mine - it certainly wasn't sold as such.

With a heat pump, you get a hot surface and a cold surface so you can play around with those - cooling damp air to get it to condense, then heat it again to get it to low relative humidity - so yes, for a heat pump containing dryer, the i'd expect the air to be dried by the heatpump.

MTBF - these days, does it matter? They are hardly worth repairing imv - any repair would cost at least 1/3rd of a new machine where I usually try to get a new 5 year guarantee. I'm afraid we're forced into a very wasteful world - although I still have my previous one which only needs new rollers for the drum, which I intend to fit one day.