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

zeupater

bushyh wrote: »

Calorex director has not submitted his report to the builder yet but response so far is

'He did say that the early indications are a frost sensor and possibly another ASHP will be his solution but he does need to do more investigative research.'

I wonder if he should come on here and do his research, seems like he might get some answers like go and work for a different manufacturer perhaps!

Hi

And according to the literature ....

"Lower limit of use to EN14511-4-2007 Outdoor heat exchanger -6ºC."
"Potential Design lower limit of use, Outside heat exchanger -15ºC"

Possibly, some of the 'investigative research' should be with the met-office ......

Looking at the performance specs in the link richardc1983 supplied and extrapolating the data, it is likely that at around -6C the maximum output of your 15kW system @55C flow will be less than 5kW and the COP around 1, so at -10C ? ... or .... -15C ?.

At a COP of 1.0 you might as well be using a fan heater, so ensure that you have a record of electricity consumption whilst it's cold (~builder to stand cost ?) .... also, get the builder to provide heat loss calculations for the property at outside temperatures from -25C (yes that is -25C !) to 15C in 5C steps as this is the likely range of temperatures where heating is required .... when the builder understands that the maximum heat output from the ASHP falls significantly with ambient temperature they might just do something ..... Also, ask the builder what the house design spec fallback option is when the ASHP becomes inoperable because the outside temperature is too low ??

HTH
Z

thechippy

Cardew wrote: »

People should read the EST report for field trials on Heat pumps - particularly on ASHPs. http://www.energysavingtrust.org.uk/Generate-your-own-energy/Heat-pump-field-trial

The study was a year long and had 29 ASHP systems from a number of manufacturers.(who installed the systems)

It is quite a long report but of the 29 ASHP systems the annual COP for 19 of the systems was 2.2 or less(the highest number had a COP of 1.6). So if that is a average spread across 12 months - little wonder systems are struggling in this current weather. In fact with the requirement for wasteful defrosting cycles, it is quite easy to envisage a situation with some systems where there will be a COP of less than 1.0 and people would be better to switch off the ASHP and rely on Granny's old 1/2/3 bar fire!!!!!!

It is also most important to note that they state because of the low water temperatures, the heating must be on much longer. This for comparison with gas/oil etc further weakens the case for ASHPs. For people who are out of the property or in bed, there is no need to have gas/oil heating on until, say 30 minutes before they get back in the house/get up; so little wasted heat. Not so with an ASHP as it has to be on for many hours while the house is unoccupied/people in bed.*

If our sensitive contributor thinks the above is Troll behaviour he should read the report and complain to EST!

* to explain if an ASHP output is, say, 150kWh in a day, that is far less effective than a gas CH output of 150kWh as the latter(with water at 80C+) is used when it is required - not when people are out or in bed.

** The COP figures quoted above are strictly speaking the overall system efficiency i.e. kWh in and kWh out.

Interesting Cardew,

As I (think) I've said before, I,ve never been convinced with air to water systems. If used, they really do have to be calculated and installed correctly and the property should have the appropriate insulation.
However, I do stand by what I've said before - in that, the most efficient form of heating is an air to air (inverter) heat pump (water, I would use on demand gas)

Too many manufacturers overstate the benefits of air to water systems....;)

richardc1983

Cardew wrote: »

* to explain if an ASHP output is, say, 150kWh in a day, that is far less effective than a gas CH output of 150kWh as the latter(with water at 80C+) is used when it is required - not when people are out or in bed.

Cardew, the central heating system at my house is on full pelt 85C flow temp radiators are boiling hot and we have massive double radiators, yet it still doesnt get the house above 20C after about 4 hours of it running.

Air to air heat pump though does this in about an hour and a half.

richardc1983

thechippy wrote: »

Interesting Cardew,

As I (think) I've said before, I,ve never been convinced with air to water systems. If used, they really do have to be calculated and installed correctly and the property should have the appropriate insulation.
However, I do stand by what I've said before - in that, the most efficient form of heating is an air to air (inverter) heat pump (water, I would use on demand gas)

Too many manufacturers overstate the benefits of air to water systems....;)

I agree if we was to have flow temps of 55C in our radiators at home we would have hardly any heating and the house would be cold.

As stated even with a gas boiler and massive double radiators with 85C flow the house still struggles to get above 20C after 4 hours.

Its such a big old house though but in a modern well insulated house Air to water is a good idea if designed and specd properly.

However air to air wins hands down. Your just heating air and the inverter systems are very quick at doing this.

Have a unit in every room if you dont want to have to leave doors open etc.

Cardew

richardc1983 wrote: »

Cardew, the central heating system at my house is on full pelt 85C flow temp radiators are boiling hot and we have massive double radiators, yet it still doesnt get the house above 20C after about 4 hours of it running.

Air to air heat pump though does this in about an hour and a half.

Richard,

Your system is atypical.

You rent a centrally heated flat, albeit the CH is iffy , and use air to air ASHP to supplement.

The vast majority of people don't want air to air ASHP systems.

They don't want to leave open doors to bedrooms and bathrooms or have a unit in every room.

They also want their heating system to provide hot water for showers/baths etc.

Let us be perfectly frank. That EST report is the first exaustive trial I have seen for UK and even the most ardent supporters of heat pumps must be concerned at the results.

To pay £thousands for systems producing those sort of results is shocking!

paceinternet

I think the EST report has been commented on in another thread in the past, but it is worth recognising that they do say:
"Results from the first year of research suggest that heat pumps can both perform well and save on CO2 emissions in many property types. We particularly recommend considering a heat pump if your home is one of the approximately five million properties that are off-gas, or for a new-build property."

There is no doubt it is a jungle out there and there will be different solutions due the costs involved for each customer. Anyone currently experiencing supply problems with lpg and oil together with increased costs will have good reason to consider heat pumps as an additional or alternative heating solution.
There are many others experiencing no heating and service charges to fix gas boiler condenser outfall frozen pipes, and componenet failures, so don't think there is a perfect alternative.

For what it is worth, I can see people like albyota have an effective system with their Ecodan's and similar alternatives.
But there are lower capital cost solutions, with savings on running costs compared to lpg and oil, for others who accept effective bivalent systems. That is a heat pump that can deliver, say 90%, of the heating requirements, and another heat source for low ambient temperature conditions.

Many people are currently paying 44p / litre for lpg, and 60 + p / litre for oil. Taking boiler efficiency into account, that is similar to electricity at 7p / kwh. Then a heat pump with anything over a COP of 1 starts to give you a saving.

Unfortunately, bushyh seems to have a system which is inadequately specified which is not necessarily the fault of the heat pump.
You are not seeing everyone going round saying, do not have a gas boiler because the condensate pipe freezes up in - 10 degC temperatures and you get no heating at all. It is bad news, and the problem has to be overcome.

bobmedley

Where do you get electricity at 7p per kw?? I have tried all the comparison sites and they state my BG Click 6 is the cheapest and I pay 9.12p per kw - that's 30% more. The lower cost makes the heat pump figures look better than they really are compared to alternatives.

Cardew

bobmedley wrote: »

Where do you get electricity at 7p per kw?? I have tried all the comparison sites and they state my BG Click 6 is the cheapest and I pay 9.12p per kw - that's 30% more. The lower cost makes the heat pump figures look better than they really are compared to alternatives.

I don't think he is suggesting that electricity is available at 7p/kwh but just stating an equivalant price for another fuel. i.e. if CH oil cost, say £2 a litre that would be the the similar to electricity costing 22p/kWh.

However in some regions, after taking into account discounts, electricity can be obtained for around 8p/kWh.

Cardew

paceinternet wrote: »

I think the EST report has been commented on in another thread in the past, but it is worth recognising that they do say:
"Results from the first year of research suggest that heat pumps can both perform well and save on CO2 emissions in many property types. We particularly recommend considering a heat pump if your home is one of the approximately five million properties that are off-gas, or for a new-build property."

There is no doubt it is a jungle out there and there will be different solutions due the costs involved for each customer. Anyone currently experiencing supply problems with lpg and oil together with increased costs will have good reason to consider heat pumps as an additional or alternative heating solution.
There are many others experiencing no heating and service charges to fix gas boiler condenser outfall frozen pipes, and componenet failures, so don't think there is a perfect alternative.

For what it is worth, I can see people like albyota have an effective system with their Ecodan's and similar alternatives.
But there are lower capital cost solutions, with savings on running costs compared to lpg and oil, for others who accept effective bivalent systems. That is a heat pump that can deliver, say 90%, of the heating requirements, and another heat source for low ambient temperature conditions.

Many people are currently paying 44p / litre for lpg, and 60 + p / litre for oil. Taking boiler efficiency into account, that is similar to electricity at 7p / kwh. Then a heat pump with anything over a COP of 1 starts to give you a saving.

Unfortunately, bushyh seems to have a system which is inadequately specified which is not necessarily the fault of the heat pump.
You are not seeing everyone going round saying, do not have a gas boiler because the condensate pipe freezes up in - 10 degC temperatures and you get no heating at all. It is bad news, and the problem has to be overcome.

Agreed! with one exception!

A COP of more than 1 does not necessarily mean a saving over normal electrical heating for those out of the house. Bear in mind the example about 150kWh. For someone working, 150kWh output from an ASHP is less effective than 150kWh used when needed as the some of the ASHP output is being produced when not required.

However anyone reading this thread, and others, are very likely to believe that ASHPs are a 'no brainer' and plenty are recommending them even if gas is available.

Unfortunately bushyh's case doesn't seem to be that unusual. Bear in mind that the systems in the EST trial were not installed by cowboys, some major firms co-operated and the results were poor.

Given the large capital outlay for ASHP systems, they should make considerable savings before being viable.

paceinternet

bobmedley wrote: »

Where do you get electricity at 7p per kw?? I have tried all the comparison sites and they state my BG Click 6 is the cheapest and I pay 9.12p per kw - that's 30% more. The lower cost makes the heat pump figures look better than they really are compared to alternatives.

EDF online saver: for a few regions.
v6 was 7.0 ish less 6%
v7 was 7.? pence less 6%
v8 is around 8.? ish less 6%