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Jon Glanfield
15-03-2013, 05:14 PM
I just wondered whether Tired Geek had any feedback on how his twin Mitsubishi system was performing especially given the winter we have (are experiencing).

back2space
20-03-2013, 01:35 AM
He participates over at the moneysavingexpertforums: Quoted from one of his posts:

"As an example my system is currently averaging roughly 2.10 a day to run at 14p/kWh.
Sounds pretty good, right?
Except that's not doing any DHW and the house temp is 10'c...."

"If you have access to mains gas then it's most likely the cheapest to run.
It's also a far cheaper system to install.

Also, as you have mains gas you won't qualify for the RHI should it ever actually come in, so the ASHP won't be subsidised in any way, therefore if it is actually a bit cheaper to run an ASHP system it'll take years and years to break even with a good gas boiler, and if gas turned out cheaper you'd never see a return.....

I can't believe I'm saying this, but put the money you save by not buying an ASHP in the building society and the interest will more than cover any higher running costs a gas boiler may have (though it may be cheaper to run gas anyway)."

Heres some of his posts:

http://forums.moneysavingexpert.com/showpost.php?p=58843509&postcount=1405

http://forums.moneysavingexpert.com/showpost.php?p=59980919&postcount=1424

http://forums.moneysavingexpert.com/showpost.php?p=60002787&postcount=1432

I've let him know of this post on the forum so he may report back over here with some more detailed info.

TiredGeek
20-03-2013, 09:27 PM
Hi Jon, sorry I didn't get back to you sooner, I don't need to come here as often now it's all working :)

It took a full removal of the "previous companies" installation, lost a few grand on the deal but it was worth it to be rid of them....

New system is working superbly, no defrost problems at all, markedly reduced running costs, and the ability to monitor the system from a distance. We're well chuffed.

COP is averaging roughly 5 over the winter while the system is on frost 'stat, but I've been watching it day by day and that COP is LOWER than it should be in reality as when the heating isn't on the heat pumps are still using electric to keep the compressor warm. This means that as one unit is mostly sat doing nothing the combined average COP is dragged down. When I check it, it can be doing COP 6 for periods when it's above freezing.
At our rate (14 p/kWh) it's costing about 2.20 / day overall while on frost at 10'c in the house.
We think that for the size, uninsulated, drafty nature and rural location of the house that's pretty damn good and certainly cheaper than our friends oil fired system doing the same job.

Since 15th December it's cost about 190 (~95 days). The last generation of the old system, just prior to being ripped out, cost 430 in 33 days of use at frost 'stat settings.
Also non of the previous versions managed to run for more than 40 days without failing, this one has run non stop since 12th July with absolutely no issues. You can probably see why we're pleased with the new units ;)

Do you have full access to the Mitsi dashboard? it's on there.....

Bigfreeze
20-03-2013, 10:08 PM
Hi Jon, sorry I didn't get back to you sooner, I don't need to come here as often now it's all working :)

It took a full removal of the "previous companies" installation, lost a few grand on the deal but it was worth it to be rid of them....

New system is working superbly, no defrost problems at all, markedly reduced running costs, and the ability to monitor the system from a distance. We're well chuffed.

COP is averaging roughly 5 over the winter while the system is on frost 'stat, but I've been watching it day by day and that COP is LOWER than it should be in reality as when the heating isn't on the heat pumps are still using electric to keep the compressor warm. This means that as one unit is mostly sat doing nothing the combined average COP is dragged down. When I check it, it can be doing COP 6 for periods when it's above freezing.
At our rate (14 p/kWh) it's costing about 2.20 / day overall while on frost at 10'c in the house.
We think that for the size, uninsulated, drafty nature and rural location of the house that's pretty damn good and certainly cheaper than our friends oil fired system doing the same job.

Since 15th December it's cost about 190 (~95 days). The last generation of the old system, just prior to being ripped out, cost 430 in 33 days of use at frost 'stat settings.
Also non of the previous versions managed to run for more than 40 days without failing, this one has run non stop since 12th July with absolutely no issues. You can probably see why we're pleased with the new units ;)

Do you have full access to the Mitsi dashboard? it's on there.....


Where are you getting your COP figures from as theres no way you're getting COP's like that on a A2W unit in winter.

TiredGeek
21-03-2013, 10:08 PM
Where are you getting your COP figures from as theres no way you're getting COP's like that on a A2W unit in winter.

Output flow temps are very low as the house is only being kept at 10'c, I'm assuming the high COP is as a result of this....

Bigfreeze
22-03-2013, 06:29 PM
Output flow temps are very low as the house is only being kept at 10'c, I'm assuming the high COP is as a result of this....

Even at a temp as low as that theres still no way the COP will be 5 or 6 at the outside temps that have been prevalent over the last few months especially heating radiators. I'd love to know how they were working these figures out?

TiredGeek
22-03-2013, 09:26 PM
I'd love to know how they were working these figures out?

I'm not, Mitsubishi is. The system is monitored and lots of data is collected from the units and analysed, I then can access it from a website. Live or archived records are available to me, the figures above are from data collected between 15th December and last week. I'm taking it as read that if the figures from the electric meters agree with the data collected from Mitsubishi regarding electric use, which they do, then the other data can also be trusted to be accurate.

Bigfreeze
23-03-2013, 12:31 AM
I'm not, Mitsubishi is. The system is monitored and lots of data is collected from the units and analysed, I then can access it from a website. Live or archived records are available to me, the figures above are from data collected between 15th December and last week. I'm taking it as read that if the figures from the electric meters agree with the data collected from Mitsubishi regarding electric use, which they do, then the other data can also be trusted to be accurate.

Yes I know, I was wondering how they were making their calculations. Do they have a caloric meter on the units because the figures they're coming up with sound wildly inaccurate? Whats your flow temp out of interest?

Jon Glanfield
23-03-2013, 09:36 AM
Hi Tired Geek, glad to hear it has worked out better this time, I looked on the Mitsubishi portal but didnt see your property listed, I wonder if it is only available to you and them?

TiredGeek
23-03-2013, 12:02 PM
Hi Tired Geek, glad to hear it has worked out better this time, I looked on the Mitsubishi portal but didnt see your property listed, I wonder if it is only available to you and them?

I think there's at least two versions of the portal, the one Google takes me to isn't the same one Mitsi pointed me at. This one has a lot more properties shown and anyone with access to this site can view a lot of data on any one of them, but I have a login which allows me to see FAR more data from my house than I see from anyone else's. I have been told not to release the link to that site but I know some people who are not on there do have access... wasn't sure if you were one of them.

TiredGeek
23-03-2013, 12:29 PM
Yes I know, I was wondering how they were making their calculations. Do they have a caloric meter on the units because the figures they're coming up with sound wildly inaccurate? Whats your flow temp out of interest?

Flow rate or flow temp? We're getting ~33L/min on the ASHP through the low loss header and ~36L/min through the heating circuits.
Flow temps have been as low as 13'c and as high as 22'c but have been sitting around 18' for 95% of the time.

I think they calculate by electric used, flow temp out and flow temp return and maybe throw in time run but I'm not that up on the technical side.

We thought it sounded too good to be true also, but we can't find a flaw in the logic.
I thought it was recycling water through the header giving a false reading but if the water flowing through the header to the rads is going faster than the water to the ASHP then the warm water can't possibly fighting it's way down a 1.5 meter long vertical pipe against this flow, surely?
It must actually be pulling cold water from the bottom of the header up to the hot flow side rather than pulling hot water down to the cold return.... I have thermometers on all the pipes around the header and the flow back to the ASHP is the same temp as water returning from the rads to the header, whereas the temp to the rads is about 2' cooler than coming from the ASHP (give or take a little for thermometer error).

One thing not considered, and one I can't comment on, is that this is a "test site". I'd say more but "Non disclosure agreement says NO"
Sorry ;)

Jon Glanfield
23-03-2013, 12:41 PM
i havent logged into the aei portal yet to see if it is on there, but will do so, have you taken it up to comfort temperatures as well?

TiredGeek
23-03-2013, 03:40 PM
Yes, we've run it for a short time at 20' and it worked well. It's been on frost for the winter though as we haven't been able to make it home, work commitments :(