Air Source Heat Pumps

stevehead

richardc1983 wrote: »

I can tell when its going to go into defrost as the air suddenly starts to blow cold and then the fan stops rotating pretty much like when you first turn it on and you have to wait for the coil to heat up before air blows.

There is also a green light on the front that either indicates thermostat off or defrost.

You can also hear the refrigerant circulating still when its like that and the coil starts to frost over inside when its gone into defrost outside.

Thats pretty handy, I've no indicator. Last winter I was guessing when mine went into defrost by looking out for high power consumption when there was no heat coming out. Not the easiest way as the plug-in meter isn't directly visible and I can't say I've noticed the effect - I'll keep an ear out for the gurgles.

mech_2

stevehead wrote: »

mech I'm saying the reason my ASHP performs so well is because Plymouth's climate is much milder than UK average. You're as far from me as Spain is - still the same climate?

No I'm not, I'm just 200 miles or so further North. Even the most northern tip of Spain is 680 miles south of me and I've no doubt the climate there is milder, but not particularly remarkable in the winter.

It's important because for the 1.5 million people who live in SW England the advertised COP performance can be achieved throughout most of the winter delivering bargain running costs. For the other 60 million of you, the results will inevitably be worse.

Simply not true: the advertised COP is unattainable for anywhere that actually needs any heating at all. Why are you so insistent on exaggerating the benefits of these systems?

Cardew

mech wrote: »

Simply not true: the advertised COP is unattainable for anywhere that actually needs any heating at all. Why are you so insistent on exaggerating the benefits of these systems?

We are back to the discussions earlier in this thread!

That is the $64,000 question!!

I suspect some of the COP figures quoted are in the "my V12 Aston Martin gets 46mpg" category. Well it might at a steady 25mph in 7th gear

I have read(no idea if it tells the whole story) that the 'killer' in cold weather are the defrost cycles.

I suspect 'in the real world' a COP between 2 to 3 is realistic in winter.

That said IMO it is a 'no brainer' if no gas is available, as getting heat one half to one third of the normal cost is excellent.

If the Government are really serious about us saving energy, it really is high time that the Government/Energy Saving Trust carried out some trials of heat pumps under controlled conditions and gave the results widespread publicity.*

Now we have to rely on claims from installers(with a vested interest) or people who have installed a system who used to pay '£5000 a year for CH and it now costs me tuppence hapenny'

To repeat, I think ASHP's are excellent if you don't have gas. Even better with a new build with underfloor heating.

I wouldn't contemplate getting Air to Air personally as it is not acceptable to me to have doors open to get heat in rooms.

The big minus of air to water is the low temperature of the water(or higher temperature and lower COP) and you have to run them pretty continuously to get the house warm. Heating Hot water for baths etc will generally have to be by(expensive) immersion heater.

With conventional gas/oil CH with water at 80+C,the rooms warm very quickly.

stevehead

mech wrote: »

No I'm not, I'm just 200 miles or so further North. Even the most northern tip of Spain is 680 miles south of me and I've no doubt the climate there is milder, but not particularly remarkable in the winter.

Simply not true: the advertised COP is unattainable for anywhere that actually needs any heating at all. Why are you so insistent on exaggerating the benefits of these systems?

Plymouth to Perth, Scotland = 531 miles by road
Plymouth to Santander, Spain = 532 miles by ferry

Source - Google Maps (by road / walking)

mech_2

Ah. I don't live in Scotland though. As I think I said before in this thread: who said anything about Scotland? Even the PDF you linked to from Sweden had figures for a site location as far South as Newcastle Upon Tyne.

(Anyway you're still closer to Edinburgh by about 60 miles in terms of latitude than Northern Spain if you calculate it properly).

This is getting silly anyway. No figures for ASHP performance have been quoted for Edinburgh, Santander or Plymouth, so their relative locations seem completely beside the point.

stevehead

mech wrote: »

No I'm not, I'm just 200 miles or so further North. Even the most northern tip of Spain is 680 miles south of me and I've no doubt the climate there is milder, but not particularly remarkable in the winter.

Simply not true: the advertised COP is unattainable for anywhere that actually needs any heating at all. Why are you so insistent on exaggerating the benefits of these systems?

Well we will have to differ on this 'unattainable' / 'exaggerating' line you and Cardew take. I am just an individual with an ASHP system; I have posted exactly how they performed for me, under real world usage over 1 year. They are in use a lot and I do require heating all day every day. I work at home, in a shirt.
Why on earth do you think I would go to all the bother of exaggerating? I'd have to be nuts to constantly fake all my imeasure readings and ashp consumption figures just to harp on about it here. I really do have better things to do you know.

I have made a decent effort to measure the COP using the formula I stated earlier in this thread. Most of the variables will be close enough, and I'm using both an infrared and mechanical thermometer to get the delta T.
The instantaneous COP at any outside temp 10C - 6C so far remains in the order of 5. This is exactly what it should be. Performs as claimed. What's the problem?

richardc1983

I do hope you have more than a shirt on Steve whilst doing your work!

Where did you get your infrared thermometer from?

stevehead

richardc1983 wrote: »

I do hope you have more than a shirt on Steve whilst doing your work!

Where did you get your infrared thermometer from?

Socks too rich!
From Maplin - 30 quid

richardc1983

No winter thermals lol? I just wear a t shirt lol went on a ghost tour of york last night... wearing only a hoody it was freezing!!!!

mech_2

stevehead wrote: »

Well we will have to differ on this 'unattainable' / 'exaggerating' line you and Cardew take. I am just an individual with an ASHP system; I have posted exactly how they performed for me, under real world usage over 1 year. They are in use a lot and I do require heating all day every day. I work at home, in a shirt.
Why on earth do you think I would go to all the bother of exaggerating? I'd have to be nuts to constantly fake all my imeasure readings and ashp consumption figures just to harp on about it here.

Consumption isn't the issue; I believe you on that, but it doesn't tell us much because we don't have anything to compare it to. I could post meticulously collected gas consumption figures from my house and they'd look a lot cheaper, but it isn't the same house in the same location, so still tells us nothing.

The performance claims are where I take issue: the seasonal COP vs instantaneous COP. The seasonal figure is what people need in order to make an informed decision on the running costs of an ASHP compared to the alternatives. For people who are using resistive heating there's no argument - obviously a heat pump is a better solution. For everyone else we need to compare the options carefully in order to weigh up the pros and cons. That means real-world performance figures and not taking advertising blurb at face value.

I really do have better things to do you know.

I have made a decent effort to measure the COP using the formula I stated earlier in this thread. Most of the variables will be close enough, and I'm using both an infrared and mechanical thermometer to get the delta T.
The instantaneous COP at any outside temp 10C - 6C so far remains in the order of 5. This is exactly what it should be. Performs as claimed. What's the problem?

The problem is it's not a seasonal figure. There are other losses not measured in a static test. We've been over all this before. No real-world test has reported a seasonal COP of 4 or more with an air-to-air heat pump. If I'm wrong on that statement find me the test that bucks the trend.