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Author Topic: Sanyo CO2 Eco 9kw ASHP - Help  (Read 35847 times)
JonG
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« Reply #15 on: December 18, 2011, 08:57:31 PM »

We have installed numerous systems where we are replacing gas for ASHP's and not one has failed to run cheaper than the gas alternative, even when the removed boiler was a condensing unit.

I would suggest that the start point is working out what your true heat loss is at circa minus 3 with the current insulation values and then checking it against the output of the unit at minus 3 and the flow temp that will suit your current rads.

You then have some information on which to base your decisions. It may be that by increasing the rad sizes and lowering the flow temps the output can match the load, if not then you could go bivalent and back the unit up with gas or at least be aware of what outside temperatures require you to light the stove to help the ASHP out.

Once you know the heat loss and the outputs of the heat pump, it may also be possible to design any insulation improvements iteratively to achieve a heat loss within the capacity of the unit.

Control wise we find that 24-7 operation, until the outside ambient hits 16 works best, usually with a night setback of no more than 2 degrees (air temps).

Also check simple things have you got the required flow rates through the system, if there is no flow meter a check of the differential temperature between flow and return and a comparison with the heat pumps requirements should confirm this. Usually this is between 5 and 10 degrees depending on the manufacturer but the rep should help with this. You may have a strainer that needs to be emptied too.

If you have a look through the MCS Installer data base and contact some local guys someone may take it on as a project even without full working knowledge of the unit, the principles are all fairly similar and we often pick up trouble shooting on units we don't actually install.

Don't give up with it until you have done the maths, the technology is sound, its usually the application/installation that lets it down.



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titan
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« Reply #16 on: December 18, 2011, 10:49:54 PM »



Once you know the heat loss and the outputs of the heat pump, it may also be possible to design any insulation improvements iteratively to achieve a heat loss within the capacity of the unit.





This sounds like installer speak to me. A house built to 1986 insulation regs will be probably be only half as good as current regs which are not that good anyway.and then there is air leakage rates quite often found to be 5 -10 times worse than current regs when tested. Insulation and leakage improvements should always be the first priority, It sounds in this case it may be possible to reduce the maximum heat load by 25% maybe more. Fine tuning the heat pump is a bonus

   
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martin
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« Reply #17 on: December 19, 2011, 12:31:35 AM »

I'll stick with my previous comments, you'll be far better off to get a proper gas boiler installed, rather than faffing about with an undersized and under-radiatored system (which would probably mean you'd still need the gas boiler to make up for the thing's shortcomings when it actually gets cold.....)
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tsh
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« Reply #18 on: December 19, 2011, 09:43:26 AM »

I'll stick with my previous comments, you'll be far better off to get a proper gas boiler installed, rather than faffing about with an undersized and under-radiatored system (which would probably mean you'd still need the gas boiler to make up for the thing's shortcomings when it actually gets cold.....)

I'll stick my neck out and suggest that you are probably not in a good position to comment on such systems, despite being an administrator on the site. Gas is an expensive short term fix, and unlikely to be any cheaper in the long run.
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Hitachi Yutaki RHUE 4.0AVHN ASHP
martin
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« Reply #19 on: December 19, 2011, 10:40:20 AM »

Having costed many systems, sometimes in collusion with those far more versed in heat pumps, I've never managed to make the sums add up for ASHPs (unless you're generating your own power from something like hydro), and over several years of this forum have come across reports of many underperforming and ludicrously expensive to run ones, and many people who have ripped them out in disgust - all power supplies will escalate in price - logically electricity will rise more than others, the grid is already faltering, so it is therefore sensible to use it only where no other energy source will do the job, and wherever possible not to use it for heating.

The original poster obviously has had a too small ashp installed as a straight swap for a boiler, and will therefore need to shell out for new radiators throughout, and sensibly a larger heat pump (if he's going to stick with it), AND a gas boiler to fire up when the temperature drops - which is going to cost an arm and a leg..... To make an ASHP perform at it's best you need underfloor heating, which he doesn't have, therefore my pragmatic advice is to go for gas (which whether we like it or not will be with us for some considerable time to come, way beyond the predicted life of a gas boiler) - it will be the lowest capital expenditure for him, the running costs will be reasonable, and should "do the job" for many years

To make the best of a gas system, he'd also be well advised to add solar hot water for spring-autumn use-  effectively allowing him to switch the boiler off for several months every year
« Last Edit: December 19, 2011, 10:55:34 AM by martin » Logged

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dhaslam
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« Reply #20 on: December 19, 2011, 12:10:13 PM »

A bit more detail on  heat pumps  using CO2 as the refrigerant.

http://www.annex32.net/pdf/presentations/Annex32_workshop_Kyoto_Stene.pdf

It is a bit tricky to read but basically  what it is saying is that the CO2 units  are designed for  superinsulated houses that need more than 50% of their heat for DHW rather than space heating.  They retain efficiecy at high temperatures but don't  reach very high COP at low output temperatures.  Also the pressure in the system is about ten times higher than  normal systems so the units are very expensive, around 10,000 for the Sanyo 9 kW unit (with buffer tank).

The electricity usage figure of  a little over 4 kW does seem very high but it does  seem to hold its output at 8kW or better according to the  brochure below and at  a COP  of somewhere between 1.8 for -15C/50C and  3.1 for 7C/50C, air temperature output temperature respectively,   so at  60C output a COP of 2.0 is reasonable.   This brochure does give a bit more technical information on the unit but they seem to be deliberately avoiding useful  COP graphs at various  outputs.    

http://www.airconwarehouse.com/acatalog/SANYO_CO2_ECO_Brochure.pdf

I think that what it boils down to really is  heat losses from the house seem to  be the problem.    Presumably the new system was installed because heating costs were high at that time with the old boiler.      

    
« Last Edit: December 19, 2011, 12:21:26 PM by dhaslam » Logged

DHW 250 litre cylinder  60 X 47mm tubes
Heating  180,000 litre straw insulated seasonal store, 90X58mm tubes + 7 sqm flat collectors, 1 kW VAWT, 3 kW heatpump plus Walltherm gasifying stove
brackwell
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« Reply #21 on: December 19, 2011, 12:38:30 PM »

Your worries seem to be cost and time to achieve temp.

A average house is fitted with a 30kw gas boiler and therefore is costing approx 30 x 4p = 1.20 /hr . When you compare this to your 45p/hr then whats the problem?  Also to equal the 30kw/hr of the gas boiler you need the pump on for 30/9 x 45p=1.50 so still not really a problem after considering the losses of the gas boiler.

As for time - thats what you would expect from a system that is only just big enough for the house requirements.  So what can be done?

The ASHP is at its limits to get water to 60C and whilst it is doing this it is inefficient and preventing heating taking place. In the midst of winter allow the pump to heat the DHW to say 35C and then set the immersion heater on a timer to reach somewhere between 45C-50C just before its main use.

Use the stovax but when not using it make sure you leave both controls fully off -we dont want heat rising up the chimney. Its possible you have one or more air vents for the stovax and the old gas boiler-block them up ! Generally go on a hunt for draughts when its windy outside.

You should have at least 270mm loft insulation -no excuse its so cheap

Turn the room temps down to 18C ( i manage on 17C). Every 1C reduces the heat requirement by 10% but also improve the COP of your pump by a similar amount !

You dont need the gas.

Ken

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martin
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« Reply #22 on: December 19, 2011, 01:06:14 PM »

Some pretty wobbly figures there - "only" 45p an hour isn't doing the job, and equates to 75 a week....... Grin
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HalcyonRichard
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« Reply #23 on: December 19, 2011, 03:15:57 PM »

Hi,
    Martin thats 45p/hour but we do not know how many hours it is on for.

As we do not know all the factors for the house it's difficult to recommend solutions. But heres some ideas.

Making sure your loft is properly insulated is a must. It's easy to do and in the 5 houses I have done it in made a huge difference. It will pay back very quickly no matter what you decide on the heating front. Any other insulation such as draft excluders, curtains etc would also make a difference.

If you decide to keep what you have got then :-

In summer hot water from the ASHP no space heating.
In spring/autumn ASHP for hot water and space heating with the logburner used occasionally
In winter I would make the log burner the main source of heat with the ASHP used as a top up

For wood heat at 100% efficiency you would need 1 Kg for 4 kWh i.e. 25 Kg on a cold day.
This depends on your life style,enthusiasm and time available. Access to free or cheap wood is also a must. If you stove is not super efficient I would consider replacing it for a larger one(possibly with a back boiler). This would enable one firing to last a long time and probably keep it going overnight.

Converting to a gas boiler may make sense if you want reliability and cheap running costs. But this has to be balanced against the installation cost. I had a friend with oil fired heating. When the gas main was put through the village a "connection cost"  of 8,000 was quoted ! So a gas boiler would have cost 10,000 - a lot to recover in running costs and you have to pay that money up front.

So what is your annual electricity bill ? And do you know the cost of a gas connectyion ?

Regards Richard
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gb484
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« Reply #24 on: December 19, 2011, 04:06:58 PM »

I am very interested in ASHPs, but before taking the plunge and buying one I would like to know how much they cost to run approx per day, particularly when it's 0 degrees outside as at present. You appear to be concerned about how much your system is costing to run but don't quote any figures (sorry, if I didn't see them). For comparison, during this coldish weather, I'm using around 11 cubic metres for ch and dhw in a 3 bed bungalow with 500mm of insulation in the attic, cavity wall insulation and 170mm of insulation to suspended floors, which equates costwise, I think, to around 4.40 per day, maybe a little bit more. My house is not over warm, 18 degrees in hallway, 20 in lounge and I am trying to be as frugal as I can without too many complaints from other family members. When it was warmer, 9 degrees outside, consumption was about 5-6 cubic metres. I've got a one-year old condensing gas boiler, and normal rads. A couple of things about your post that I would like to perhaps echo: as others have pointed out, your dhw doesn't need to be 65 degrees, that temp can cause scalding. What happens with the ch if you switch off the hot water for a few days? From what I've read about ASHPs, you should run them 24/7 to provide a constant low level of heat, and the lower the flow rate, the better the COP, so try turning it down to a level that is perhaps a tad too cold, then slowly nudge it back up until it's better, to find a happy medium. Upgrade your levels of attic insulation, if possible. Think about fitting convector rads, but really, 20 degrees is reasonably warm. Use the woodburner more to supplement ch when it's really cold outside.
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titan
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« Reply #25 on: December 19, 2011, 05:00:48 PM »

This link  is on this site somewhere else but it gives live data from a Sanyo Co2  4.5 kW unit the COP does not look that impressive to me.  http://www.elisanet.fi/sanyoco2log/
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MacBeagle
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« Reply #26 on: December 19, 2011, 05:12:31 PM »

As promised, pictures of the Settings/Display panel taken last night
https://picasaweb.google.com/107578057515193397049/SanyoCO2SettingsAndOutputs?authuser=0&authkey=Gv1sRgCIHc963EttiSEQ&feat=directlink
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MacBeagle
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« Reply #27 on: December 19, 2011, 07:03:21 PM »

As you can see from Diagnosis Menu 2 the HP water out is 65 and the rad temp in Diagnosis Menu 1 is 40 and the tank temp is 39 - why is this and where is the 25 going?
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Countrypaul
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« Reply #28 on: December 19, 2011, 07:19:24 PM »

Have you check the temperatures independantly to ensure the readungs are correct?
How well insulated is the pipe from the HP to the rads?
Could the radiators be sludged up causing a poor flow through them?
Could the pump be operating poorly? Can you test it?

Losing almost half heat you need before the radiators suggests there is certainly scope for some changes.

Paul
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Solal
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« Reply #29 on: December 19, 2011, 08:12:45 PM »

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 -

Has the compensating curve  to the heating system   been set up correctly?
Do you know  what its currently set at?
« Last Edit: December 19, 2011, 08:23:03 PM by Solal » Logged
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