ASHP – Should do better - Must Do Better

muckybutt

Cardew wrote: »

Getting rid of? or getting?

Getting RID of ie its being taken out ! and the sooner the better in my eyes !

henryc148

Hello
I am new to the forum. Very interested in the comments about ASHP.
We installed a Mitsubishi Ecodan had it commission in October has worked for 3 weeks nothing but problems so far. I didn't quite work out cost when working but I did notice an alarming rate of electricity being used. we are in a victorian London property so our next stage will be having new windows, my main concern is that from some of the user reviews, these ASHP's don't seem to be worth the trouble, as compared to a gas condensing boiler!

grahamc2003

henryc148 wrote: »

Hello
I am new to the forum. Very interested in the comments about ASHP.
We installed a Mitsubishi Ecodan had it commission in October has worked for 3 weeks nothing but problems so far. I didn't quite work out cost when working but I did notice an alarming rate of electricity being used. we are in a victorian London property so our next stage will be having new windows, my main concern is that from some of the user reviews, these ASHP's don't seem to be worth the trouble, as compared to a gas condensing boiler!

I've read a lot recently on ASHPs, and I'm not sure I've read that they are sensible to use if gas is available. It's worrying, but understandable imv, if the best systems like your Ecodan, experience problems - I assume it's only at low (freezing and below) ambient temperatures where this is a problem? Aiui, Econdans don't have electric heating elements built in - others have 8kw apparently - so surely you can't have the massive bills others have reported?

I think the problem is fundamental. These big systems with a single outside unit have an almost impossible job to do imv. Extracting something like 10/15 kw from freezing and below air is very difficult for a couple of obvious reasons. Firstly, air has a low thermal capacity, meaning you need lots of it, hence very large fans I expect blowing very hard to shift the required quantity of cold air over the heat exchanger when a high output is required (like when it very cold!). Secondly, the killer seems to be icing of the heat exchanger - obviously, throwing loads of air over the extremely cold refridgerant instantly builds up ice, which has devastating effects (both on the efficiency of the fans, and the insulation to the incoming air, hence the defrosting strategies these things employ (sometimes very badly it appears).

For my part, at the moment, I would avoid any high powered units. The lower the power, the less likely those inherent problems are likely to show. For the same reason, I would go for a single inside unit for a single outside unit, and also only consider air to air, which is much less demanding than 'complete solution' types.

If I had an Ecodan, and much more so if I has a lesser model from lesser manufacturers) and it was extremely cold (or humid), I'd be tempted to turn the thing off if I saw frequent (or continuous!) icing of the outside unit, since it isn't going to work anyway, or at best produce a small amount of heat for a lot of electricity). If only moderate icing was occuring at above freezing temperatures, I would lower the demands on the unit (i.e. by setting a lower inside temperature and/or turning some internal units off) in the hope of eliminating icing.

But today, at 11degrees here, the system should be producing very cheap heat. Is that the case?

richardc1983

Agreee with thechippy on all of his comments. I prefer how air to air systems run. I like the heat delivery in that you have instant heat and fast.

If I was doing my house I would have ducted upstairs and individual units downstairs, and why would this be any different to having radiators which you have in every room a small unit in each room smaller than a radiator is ideal.

Not everyone likes warm air blowing though so each to their own.

thechippy

Good point about the radiators Rich.

All mine are in places where they are a blasted nuisance quite frankly.

High level small wallmounts are not in the way of anything....:D

richardc1983

thechippy wrote: »

Good point about the radiators Rich.

All mine are in places where they are a blasted nuisance quite frankly.

High level small wallmounts are not in the way of anything....:D

Same here my 6 seater sofa is in front of the radiator as no where else to put it, its on the longest wall. Same at my parents house.

Cardew

Some of the bad experiences people have with ASHPs should be put in this thread: Perhaps this should be a Sticky as well!!!!

From MICKY BUTT
Update on this P O S.

Weve had it in a while now and its goto be the WORST decision we've made having this put in.
We were advised to leave it running 24/7 for it to be more economical - which we did, the alarm bells rang 6 months after it being fitted when the electricity supplier rang us up asking if we were expecting a big bill ? when we got the bill we were bowled over £800 for 70 days use.
Since then we only have it on in total for 4 hours a day and itsstill costing us £200 a month.
If anyone wants to buy an ASHP then ive got one going cheap...buyer to collect. We're getting rid of the bloody thing and getting a wood burner stove, far far cheaper to run.

lovesgshp

muckybutt wrote: »

Getting RID of ie its being taken out ! and the sooner the better in my eyes !

The spec on your unit looks quite good from what I can see. I presume you are using radiators and if so is there a buffer tank? What temp are you keeping the house at, as this can affect running costs considerably?

albyota

Air to Water Heat pumps range from 'very cheap' non inverter driven (converted swimming pool heat pumps) or rebadged far eastern rubbish, IMO, to quite expensive Japanese / european models, inverter driven, large fan coils, weather compensation sensor, flow temerature monitoring, minimal defrost cycles ('self learning'/'fuzzy logic') etc.
It is a fact that heat pumps work at their most efficient at lower water temperatures.
It is also a fact that even though most of the better manufacturers systems are guarateed to operate down to minus 15 to minus 25 degrees, at minus 7 the performance can reduce by 1.5 - 2 kW of the rated output. i.e. at minus 7, a 14kW system would reduce to 12.3 kW output, but still provide water at 45 degrees due to low ambient temps, (high humidity) defrost cycle.
When sizing an ASHP, calculating the heat loss/load for the house, it is important that the house is well insulated, good double glazing, loft insulation to 270mm, and free from draughts, you must consider the external ambient conditions, (i.e size to 'say' minus 7),
ASHP's are most efficient with under floor heating, however, when retrofitting, where radiators are to be used, it is important to measure the existing rads / output and calculate the correct size for the lower temps 45 degrees, using radiator manufacturers output tables/formula.

on MSE we are reading an increasing number of 'unhappy' end users saddled with the cheapo system which has just been 'bunged in' to satisfy the 'green blingers' or 'sold' to the unsuspecting builder/developer/tenant/client by people who don't either know how to specify the equipment correctly, or install it properly, or even know how to commision it to its most efficient setting.

This is a money saving forum and whilst I appreciate and sometimes agree with the title of this thread, I think it should not be used to slate all ASHP's in general, we have read about hideous costs, systems struggling to provide any heat at all, the energy saving trust trial carried out in 2008 was for 29 systems, I personally know of over 60 installations carried out in 2010 with only 5 of those with poor results mainly down to their refusal to upgrade some of their radiators, and a couple of systems with high heatloss from large glazed areas, or poor insulation.

The best thing about this site is being able to discuss these topics and for us all to learn from the varied information and to make our own educated decisions on the facts.

If someone has a bad experience from their system, they should also state Make/size of unit size/type of house it is in, insulation levels, Double glazing type, cavity wall insulated, is it providing DHW?, heat emitters, (radiators/UFH), and if the electricity consumption includes all other appliances.

Rather than, 'it has cost me £xxx for xx days... it only cost me £xxx on oil last year. This is a rubbish comparrison as this year was much colder for longer but it happened at a different month, last years fuel prices were lower, if you were still using oil you would have used more, costing upto 70ppL.

Please, Lets keep it informative, and using true facts.

I have had my Ecodan for over three years, house always warm October to April, running UFH at 36 degress and DHW 55 degrees, family of four, electric cooking, daily dishwasher, washing machine 5 times/wk. plus all other standard usage.
Village location, Off gas grid.
20mm double glazed, cavity wall insulated, 270mm loft insulation
2008, total house fuel bill using oil and electric £1450
2009 total house electric bill £837,
2010 total house electric bill £933, coldest winters!

lovesgshp

Thanks Albyota. I agree with your comments totally. It is always better to have the full facts concerning any heat pump installation. I solely work with geothermal units, so I think much more factual information should be given regarding the operation that people complain about.