Sanyo CO2 Eco 9kw ASHP - Help

[HalcyonRichard]

Hi MacBeagle,
             It's good to see you are experimenting with your system. Every house,heating system and inhabitants are different. Reading between the
lines you seem to have a similar insulation and heating requirements as me. I have experimented over a number of years to optimise efficiency while
maintaining comfort levels. Initially I tried just putting the heating on when required but this meant the fabric of the house was usually cold and
required a higher thermostat setting to feel comfortable(always above 20 C).

I built an extension onto my current house it is now 1/3 of the completed house. I barrowed in the cement for the new "slab" - six tons of it ! So the
whole house slab is probably 18 tons of cement. I carried in the platerboard into the house basically a pile a metre high probably another couple of
tons.The internal walls are solid brick so many more tons of thermal mass. With water pipes furniture crockery kitchen units and much more stuff. This
could easily add up to 50 tons of thermal mass to heat up.

This was brought home to me when I went on holiday for a week in March. No frosts were predicted so I turned off the heating and electricals. Coming
home on a warmish day the house was colder than the outside. The internal temperature was 12 C. Even though we put the heating on the house felt cold.
Everything we touched was chilled cutlery cups etc. It took at least a week before the house felt comfortable. Considering the tonnage of material to
heat this is no surprise. The air temperature was 20 C+ but it just felt cold and draughty.

Although the thermostat is controlled manually I keep the house continuosly between 16 C and 20 C(average 18 C). It feels comfortable and draught
free. Some years ago on the forum there was a discussion about heating continuosly versus heating when required. It was never really decided which was
best for economy. Everyone who maintained an even temperature reckoned it was cheaper.

Over the last year October 2010 to October 2011 my gas heating bill has been £504.66. I use about 40 kWh/day on average With probably the coldest
winter for 20 years included in the year. I am well pleased with this.

Strangely I run my system with a water temperture of about 50 C and maintain the house temperature all the time. This is usually recommended for heat
pumps. You seem to be setting up your system on a timer with fall back temperatures wihch is usually recommended for gas/oil boilers.

Also it is interesting to note that my 40 kWh/day usage is probably at a boiler efficiency of 75% (non condensing boiler) So the actual heat input is
30 kWh/day. If you achieve this with your system it will cost :-

Assume average COP of 2.5. electricity require = 30/2.5 per day = 12 kWh/day
Assuming a cost of 10 p/kWh this equals 12 X 0.1 = £1.20 per day (average)

This is 1.20 x 365 = £ 438 per year. So assuming gas at £0.035 and electric at £0.10 the heat pump is cheaper to run assuming same output is required.

Out of interest what is your yearly bill ? And do you have a cost for connecting to the gas main ?


Regards Richard

[Solal]

Hi
compressor speed 65hz
outside air tempature 2
room tempature  14
the compressor should be runing at almost full capasity ?

It can't, because the flow rate is not allowing any more heat to be taken away. Pump demand is set as a result of output temperature of the heat transport fluid.

If its  say zero degrees  outside and the compensator  is asking for a discharge  flow temperature from the HP  of 65c  and a wide  differential is  between  the return and the target  temperature   then surely  the compressor   should be ramping up full  to try and narrow the differential?

As the differential  narrows  with the  return  climbing  to say  60c  then I would have thought  this is when  the compressor will start ramping down  to maintain lets say a 5 degree  f&r differential.

[clivejo]

I might be missing something but all your values are nowhere near the targets in brackets.  But your ASHP is still running trying to meet the demands.  This suggests that it is undersized for the demands on it  However I have seen this in fridge/freezers where the compressor is running excessively but never reaching the desired temperature and it was because the gas level was too low.

Have you had the refrigerant gas checked?  With it being CO2 and higher pressure, it makes me think the gas will escape quicker!  Does the manual give any indication on how often the CO2 needs to be recharged or even renewed?

[JonG]

Halcyon Richard, its an interesting debate the continuous versus timed, a thread on the Green Building Forum has examined the same thing and the consensus was that mathematically there should be no difference.

However I am fairly sure that if I drove my car at a steady speed as opposed to accelerating and breaking regularly I would use less fuel. We have customers who have researched the same issue with heating in the lead up to a heat pump install and generally their feedback is that the fuel usage is lower.

Not only that but the thermal shock and cycling of a timed system cannot be good for any technology.

We always set up heat pumps to run 24-7 perhaps with some setback to preserve the compressor but inverter driven manufacturers have confused installers by suggesting that the modulation will take account of ramp down in the same way that a modern gas boiler will, but the reality is that it is usually 30-50% of output which can easily be exceeded in a zoned system or in the shoulder periods of the year.

[baker]

CLIVO
the demand is not  full on

[Panda]

MacBeagle, I hope you are making some progress with this.

Keep in mind that there are two pumps. The one that is labelled CP Pump is the high head low flow pump that is directly underneath the thermal store. It is responsible for trickle charging the thermal store and its speed is controlled by the tank unit controller. The water coming out of the heat pump outdoor unit is at 65 degrees and the water returning to the heat pump outdoor unit is 41 degrees. This differential is a bit on the high side (I think it should be a 20 degree differential for these type of CO2 refrigerant heatpump) so it may be worth checking this pump. I think there is a manual speed selector on the actual pump (i.e. speed 1, 2 or 3) and I believe it should be on speed 3 which would allow the tank unit controller to modulate the pump speed over a proper range.

The other pump is your radiator circulation pump which will be mounted externally to the tank unit. This may be "interlocked" with a roomstat to stop it from wasting power when there is no further demand for space heating (or it may just run all the time if the installer didn't realise)

Your thermal store is at 49 degrees at the top so you ought to be able to send 49 degrees to the radiators. Are you able to confirm this? if the radiator flow pipe is significantly less then I'd say the problem is with the control of the 4 way mixing valve. You could drive it manually using the knob on the front of the mixing valve (turn the knob fully clockwise I think) and see if the radiator flow pipe gets hotter.

Finally, once you know that your radiators are being supplied with the highest temperature that your tank is at you might have to enable the electric immersion heaters within the tank unit controller in order to achieve your desired room temperature during cold weather.

[baker]

  a other possibility may be
the working medium output flow rate is restricted  at the mixing servo valve by the set regulation parameters
increasing the output temperature

[MacBeagle]

Thanks for all the replies.

Trying to take it all in but we have honed the 24/7 mindset to setting the thermostat/timer in the house on manual and have it set at 15° just to see how that pans out. The outside temperature at the moment is 10 so its no test at all really - we used £2.78 in the last 24 hours and we are an all electric house. We are both semi-retired so we spend a lot of time at home using multi and various electrical gadgets therefore it's a bit difficult to pin down exactly how much the ASHP is using.

I will enquire about the CO2 gas needing a top up but there is nothing in the "manual".

It would be nice if someone from Sanyo could come down, stand in front of the unit and explain in layman's language exactly what each bit does and why.

Panda. We did use the immersion in the tank to get the temps up last winter but the cost was astronomical.

[dhaslam]

Do you have the facility to just heat top up the DHW temperature with the immersion without having to heat the radiators as well.      A well set up system should  be able to have  the radiator take off point lower down on the store and a facility to heat the top separately.  Also  do you have  lower electricity at night?    If so you could top up the temperature in the early morning with the immersion but have the normal  flow temperature a bit lower.

I am not using my heat pump any more  but  in early December  last year  I was using 5 kWh each day to top up DHW temperature and that was mostly at night rate.     This week last year of course the  temperature was too low to use  the heat pump at all so electricity use got a bit out of hand.   

[HalcyonRichard]

Hi MacBeagle,
                Thats interesting. Over time I have found out it can take up to a week to see the benefits of a stable temperature. For instance my 50 tons of thermal mass in my house would require 140 kWh to heat by 10 C. This is two days normal heating consumption.

Your figure of £2.78 should really be in kWh (at current prices/tariffs/economy 7 it can be misleading). So earlier you said you paid about
10 pence per KWh. This equates to about 28 kWh. If you are average electrical users you will be using 10 kWh on gadgets.

So 18 kWh to the heat pump at say a COP of 2.5 equates to 45 kWh out put. Say 6 kWh for hot water.

This means 39 kWh for heating. This is not unreasonable But one swallow does not make a summer. My figures are guestimates of course.

Also your temperature of 15 C seems low, you should be feeling the cold at that. Thermostats can be "out" by a few degrees. I checked mine by using
two other thermometers - they were all within 1 C of each other. Also the position of the thermostat is important height and position. If it's in
a cold spot the house average could be higher that the thermostat is set at.

It might pay to buy an energy monitor to see what your gadgets etc use. I replaced an old TV with a modern one which cosumes less than 1/3 of the old
one. It will make working out the power used for heating easier.

The national average household consumption electricity and gas is some thing like £ 1500 (mine is 1/2 of that). If you come under this on an all electrical house
you are doing very well.



Regards Richard

[MacBeagle]

Hi HalcyonRichard

"Also your temperature of 15 C seems low, you should be feeling the cold at that."

Nah, toasty. We are old school, bought up when you only heated one room and froze going to the upstairs loo. The good old days - rickets, diptheria, scarlet fever.

It's no hardship at 15 and that leaves a good reserve to up it a bit when the temperature drops, and we always have the Stovax. Just wish a) I had found this forum earlier and b) the people who sold us the unit were as well informed

[HalcyonRichard]

Hi,
    Thanks JonG I have had a look at the green building forum and joined ! Over christmas I found out that on permanentley certainly appears to be more efficient than on/off control

One night it felt chilly and draughty at 20 C but over the next hour it felt warm and still with no draughts at 20 C. So I thought has the house thermal mass finally reached equilibrium ? So I decided to leave the thermostat at 18 C for a week to check things out. Three days of similar weather and daily consumption is 48 kWh i.e. 25 % less with heating on "permanentley". The boiler seems to fire for 10 -15 minutes every four hours or so. Early days I know. The house now "feels" very different and seems to hold it's temperature very well. This made me think. I have to get to the bottom of this. I think I am on the right track and will post what I have found after I research the physics/thermodynamic principles to back up my thoughts. It seems that natural convection could explain a few things. I am posting on the green building forum on this thread :-

http://www.greenbuildingforum.co.uk/forum114/comments.php?DiscussionID=8179&page=2#Item_15

Regards Richard

[MacBeagle]

Have been persevering with the constant 15°C, boosting it to 17 in the evening and using the Stovax every now and again. Works fine but, and it's a big but - during the early hours the thermostat will keep clicking on and off when it reaches 15°, the pump kicks in for micro minutes and the radiators start clicking - it's driving us mad. The pump and thermostat are hardly discernible but the clicking rads are something else. Would modern rads eliminate this?

Just got some figures from nPower about my electricity usage from June 2010 - June 2011 which encompassed some minus temperatures and usage of the immersion heating elements - 11,846 Kwh total energy bill, which equates to £1293.14 (Sign On-Line 22). They reckon we could be spending roughly £1400 for gas alone based on an average 4 bed house. So, real food for thought.

[MacBeagle]

Hi

Looking at Dimplex Smartrads as an alternative to the old slimline radiators to make the most of the ASHP.

This is a question for StationHouse really but feel free to chip in. In one of his posts he said "we went for the white glass fronted Dimplex SmartRads. Size them at the lowest fan speed to the room so they run at their quietest." How did you do that?

Cheers and a Happy New Year to you all

[StationHouse]

Hi

Looking at Dimplex Smartrads as an alternative to the old slimline radiators to make the most of the ASHP.

This is a question for StationHouse really but feel free to chip in. In one of his posts he said "we went for the white glass fronted Dimplex SmartRads. Size them at the lowest fan speed to the room so they run at their quietest." How did you do that?

Cheers and a Happy New Year to you all

Hi, if you don't mind I'll get back to you shortly about sizing as I'm tucked up in bed  Certainly SmartRads/fan convectors are the way to go if UFH or hughly oversized rads are out of the question. Now we have lived with the system for a while the one thing I like is the fast response of the system as each rad only holds about a litre of water whereas oversized rads would hold vastly more. UFH may hold even more water but the advantage there would be running the system using cheaper overnight electricity tarifs with the slab holding the room temps during the day with minimal topup?

Running cost wise Dec 2010 with a mix of snow, hard frost and semi mild has been just over £100 for the whole house. Not bad for an old house with 3m ceilings. Last Dec mimimal use of LPG for Dec, although colder, would have been around £300 plus electric for oil rads...

Put it this way, our bed still has the thin summer duvet 

Happy new year all