Sanyo CO2 Eco 9kw ASHP - Help

[MacBeagle]

Hi

We live south of Bristol in a 4 bedroom detached house, which we have lived in since it was built in 1986 - oil fired boiler originally as there was no gas piped to the village (there is now). It is fitted with mahogany double glazed units, suspended floors with downstairs underfloor insulation, thermal block inside wall, CWI and the loft is floored with chipboard over standard 1986 insulation and full off "stuff". Stovax 4.5Kw multi fuel inset stove for emergencies

Our hot water/heating system is a Sanyo 9.0kw CO2 Eco ASHP which was fitted in Dec 08/Jan 2009 and linked up to 13 existing radiators. The hot water side of it works fine but the heating is struggling to reach 20° even though we are getting tank temperatures of 65° - it has to be left on for a long time to get to that temperature and consequently costly. The original installers are not around anymore so I am at a loss to get any useful information - the nearest Sanyo heat pump rep is in Nottingham.

It seems from reading a lot of the posts in this section that I have a worst case scenario - inefficient rads and heat loss problems.
So, given that UFH is not an option:
a) What else can I do to improve/stop heat loss?
b) Does the floor-boarded loft and all the "stuff" constitute insulation or do I have to up the depth and raise the loft floor?
c) What constitutes a suitable radiator or is there another form of outlet that can be fitted?
d) Do I throw in the towel and fit a gas boiler?

[martin]

If you are fortunate enough  to have mains gas, go for "d" asap!
To fit an ashp  to an existing rad system is just plain bonkers - it'll cost far more to "put it right" than get a decent gas condensing boiler

[baker]

what size house have you
 if you are stuck with the heat pump
you could change one rad ,   to  forced convection rads and see the outcome/
try  ,solo rad  smart radiators have 15mm connections both on the one side  and need a 3 amp supply
to run fan and intergraded temperature controller, and also looks hot
also java do a basic  convector rads
 
it a good idea to ditch the heat pump if you can
if you have mains gas   
i sure their is a connection fee to consider and the cost of a a rated boiler ect
baker

[itsnewtome]

There are plenty of low temperature rads on the market now especially designed for heat pumps.
They have a lower water content and different designed fins etc.
Have you tried flushing the rad system?
Get the Sanyo rep to have a look he may point out something
Has it always struggled or just a recent issue?
Ther will be costs involved in getting a gas main in

[dhaslam]

It may be that all the heat is going to  hot water.  The problem with this is that with low air temperatures  the heat pump will struggle to reach that temperature and leave no heat for the radiators if DHW gets priority.      You could try setting the  DHW controller to a much lower setting and  if you have an immersion use it to bring thje water temperature up.    If  it works as expected you should start to get some heat in the radiators.   

Ideally this kind of system should be used to heat a buffer tank with off peak electricity, this would allow  heat to be used from the store when you need it  but it  probably is only capable of providing heating and very hot water when the outside temperature is warmer.   

[MacBeagle]

Thank so much for the replies, it's a bit lonely owning a Sanyo ASHP in these parts.

We would like to hang on to the ASHP investment if possible, and I do like your suggestion of low temp rads. We are perfectly comfortable with the house at 18° if only it would get there a bit quicker and we could solve the heat loss problem, it real does drop quickly when the heating goes off. It's just weighing up the cost of 13 new rads and the hope that they will make a difference against gas conversion - we would have to have the supply moled under the back garden from the main in the road.
And yes, it has always struggled.
dhaslam - the unit has got a motorised mixing valve that should control the temperature to the radiators at every outside temperature, but the setting are so complicated (to me anyway) that nobody has been able to give me a satisfactory explanation of the optimum settings for my house - unless the rep stays for a couple of days its a case of suck it and see.

[desperate]

Hallo MacBeagle,

you say the house cools really quickly when the heating goes off, that is your problem more than the type of heating system I believe. You have already pointed out the loft insulation is to thin, I would start there, would it be possible to bolt some 4*2 joist on top of the existing ceiling joists, this would give you room for more insulation, a cheap and worthwhile thing to do. I would bolt the new timber along the existing joists not across them, this is a stronger option. Also concentrate on draughtproofing as best you can. These sort of improvements need doing whatever you decide to do with the heating.

Desp

[dhaslam]

the unit has got a motorised mixing valve that should control the temperature to the radiators at every outside temperature, but the setting are so complicated (to me anyway) that nobody has been able to give me a satisfactory explanation of the optimum settings for my house - unless the rep stays for a couple of days its a case of suck it and see.

The idea of  the  variable  temperature mixing valve is that it raises the flow temperature when the outside temperature falls.    The problem with this is that  when it is cold  outside the  output temperature  of the heat pump also falls  so it can't reach  the set temperature  unless the load is very light. Thirteen radiators would need 13 kW  at a high flow temperature plus another  one or two kW for DHW and the output of the unit is probably something like 5 kW.  I am only guessing the output because their brochure seems very vague about the  output.     

The Co2 system is better than most heat pumps  but they all do suffer a bit from poor performance  in cold weather.     If you can turn off some of the radiators, specially the ones that can be heated with the stove  wou may be able to get the system a bit hotter.   

The Co2 heat pumps detail are near the  bottom of this document. 
http://www.oceanair.uk.net/pdf/SANYO_Heating_Brochure.pdf

[titan]

It is not clear from your post whether you have cavity insulation or not. Thermal blocks were the result of good lobbying by the building industry so they could continue to build poorly insulated houses the way they always have while paying lip service to improving regs. If you don't have it installing it along with at least 300mm of loft insulation will noticeable improve your heat pump  performance. You also have a stove, it it room sealed. I don't know who specified your pump but 9kW also sounds a bit small for a large detached house with 1986 insulation values.

[Solal]

Only use an air source  heat pump in the UK  when outside  temperatures  are above 7C  unless ufh is fitted  and the home is super insulated  in which case a candle should  heat it anyway.
These  things must be the greatest failures ever  brought into the uk heating market.

[tsh]

Lots of posters here telling you that your system is wrong - not many asking if it has only recently started to cause problems or asking anything specific. There isn't necessarily any good reason not to stick with this system, although it is correct that improving your insulation will help. Look into 'space board' for the loft. It may be cheaper/easier than the timber to add more insulation.

You shouldn't be getting hot water at 65 degrees - this is not really necessary, although I can confirm 45 is too low (trying to get round the DHW priority and forgot to set it back to 51)

Be aware that trying to make a heat pump run Hot/off is not going to work well. Mine takes about 2 hours to get from 18 to 21 degrees - into radiators  

Check that it is really switching to heating the radiators, and if you can come back with the flow/return temperatures to the heat pump. Due to the variation in efficiency, it is better to have the pump running at 35 degree output all day rather than 50 degree output for 6 hours a day (roughly - in practice it depends!) Certainly, you probably don't want to let the house drop below 17/18 degrees if you want to to be warm again in the next 12!

Edit: Just noticed that this heat pump can run up to high temps without too much trouble - although it is probably still more efficient if it's running cooler.

[martin]

There's several good reasons not to stick with the system, most of which have already been pointed out - the heat pump would appear to be undersized for the job, there is no UFH to make the most of the low grade heat that it does produce, it would cost a small fortune to replace the pump and provide oversized rads throughout, so it would be far more pragmatic to ditch the bally thing altogether and get a decent condensing gas boiler which is suited to the existing radiators. Shame the company who supplied the system isn't in existence as I feel they let their client down badly, and should put it right (but if this is the sort of job they did, not surprised they're defunct as a company).
Obviously, whatever is done, it should be allied to insulating to the max.... I reckon that the cost of the new boiler would very soon "pay for itself" in savings on fuel costs

[Countrypaul]

It appears that before making a decision on what to do (other than add more insulation which should always be first), gathering some more information on your usage might be helpful. For example, is it turned on 24hrs a day and if not when is it on, how much electricity do you actually use in running the HP, can you put a simple meter on to measure it? Does the heat pump cycle on and off frequently, if so then it is certainly not being utilised properly. What temperature is the feed into and out of the HP measured independantly of the pump?

If trying to use it like aGF central heating system, then the results would be disapointing.

Paul

[HalcyonRichard]

Hi,
   It sounds like your output is undersized for your radiators/insulation levels.

If it's 9 kW system when the conditions are perfect you will be unlikely to get this in poor winter conditions
when you need it most.

I have a four bedroom detached bungalow with gas combi and good insulation. In cold weather it uses 100kWh per day to heat.
This is 4kW on average. My boiler is rated at 30 kW.

You have twice as many radiators and probably worse insulation. But your ASHP probably gives you 5 kW in winter.

After a cold night in my house with the heating off it can take 2 - 3 hours to warm up my house.

You have twice the radiators and roughly 1/6 the power input so roughly 12 times the heat up time.
i.e. 24-36 hours.(I know there are a lot of other factors involved as well)

For the hot water you have about 4kW. This compares well with an immersion heater at 3kW.
So I guess a couple of hours heating your water tank should be noticeable.

I would guess that your heat pump will just about keep your house warm once the set temperature is reached.

Also it is interesting to note in cold weather you probably need to run your pump continuously if it is
your only heat source.

Do you know your electrical consumption for the winter months ?

Regards Richard

[MacBeagle]

Thank you so much for all the replies. I have just got in and wow, what a forum, so much help. Will have to read them all carefully - but in the meantime - the system is on as we speak and according to the Smartpower meter the unit is using 0.45p per hour irrespective of any change in settings. This is based on 10.30p per unit + a daily standing charge of 20.27p - nPower Sign Online 22. We use it much as we did our oil boiler i.e. twice a day and the compressor is on continuously during those times and the unit is having to defrost quite regularly. I will note down all the settings tonight and post them tomorrow to give you some more information to go on.
Again, all the advise very much appreciated.