Posted by: @tufty

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Hi

Ive just taken a reading from my Ecodan. I dont need heating, so put it on defrost mode on my handheld thermostat 8 week ago.

Over the last 8 weeks the ASHP has used consumed 198Kwh, much of that is on heating, even though I have the heating turned off. 

Is there another way to disable the heating? The Ecodan does say that its heating is prohibitive.

At the moment I have only have the DHW come on once every 2 days to heat the cylinder for showers/washing up. (Im a very low user), so not sure why the heating is coming on at all.

Thanks

 

 

Hi @tufty

I believe the Ecodan automatically adds about 2.8 kWh per day to the ‘energy used’ data. I spoke to a Mitsubishi engineer recently who said this occurs when the ecodan is in standby mode. However the energy hasn’t actually been used. He couldn’t tell me if this was a one off daily amount or a proportionate amount depending on cycling frequency. 

It sounds like this might be happening with your unit. (198kw spread over 8 weeks equates to about 3.5kw a day)

If you had some defrost cycles in April you may have had additional values added to the energy useage data. Mitsubishi say it’s an estimated energy useage calculation  and is not an actual metered reading. 

This is an irritant for anybody trying to view performance of their heating system since the COP calculation is derived based on the inaccurate energy used data!

I guess a small comfort might be that your daily energy useage may be 2.8 kw less than the recorded data. So you could manually correct your daily energy used and work out a different COP for your system…. After all it would be just as accurate/inaccurate  as the Mitsubishi calculated estimate… wouldn’t it?

Second Guessing (I’ve been trying to imagine why this 2.8 kw might be added to a daily consumption file and I think this might be linked to cycling which if happens frequently does literally reduce the efficiency of the heat pump. So it might be that regular cycling through the day might add up to an average energy loss of 2.8 kw  However if stand by mode is seen as cycling - if this were the case -  the 2.8 kw add on would be completely unnessessary. In the end it’s a correction factor that Mitsubishi have built in)

@sunandair Thanks for that answer. Very useful, and hopefully this is what it is.

Im pretty sure its adding the kwh to my main meter (not sure how I could actually check) so presumably Im paying for that energy that Im not using. 😐

Like you say, it completely skews the figures!

While I was in the garden the other day in the midday sun, I did hear the fan switch on, even though it was at a different time to what Ive set on the DHW schedule. I thought it odd as theres no reason (that I can think of) why it would come one. Ill never understand this system. 😐

Posted by: @tufty

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@sunandair Thanks for that answer. Very useful, and hopefully this is what it is.

Im pretty sure its adding the kwh to my main meter (not sure how I could actually check) so presumably Im paying for that energy that Im not using. 😐

Like you say, it completely skews the figures!

While I was in the garden the other day in the midday sun, I did hear the fan switch on, even though it was at a different time to what Ive set on the DHW schedule. I thought it odd as theres no reason (that I can think of) why it would come one. Ill never understand this system. 😐

 

If your electricity supply meter is recording energy usage, then it must be being used somewhere, since energy cannot be created or destroyed, it can only be changed in form.

If you have a Smart meter and the time, you could monitor usage and look for unexplained increases. Alternatively you could take hourly readings from your mains meter and again look for unexplained usage. Then check what the heat pump was doing at the time.

Posted by: @tufty

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Thanks for that answer. Very useful, and hopefully this is what it is.

Im pretty sure its adding the kwh to my main meter (not sure how I could actually check) so presumably Im paying for that energy that Im not using. 😐

So if you can isolate additional energy use coming from your heat pump there cold be various things happening. This is difficult to advise on without knowing quite a bit about your existing settings. And also your personal experience of accessing the menus on your main controller. 

some examples of erroneous energy use might be:

• Freeze stat function set too high
• DHW temperature too high so needing immersion heater assistance
• Legionella setting activated frequently 

etc. Of course it might be none of these and what you are seeing is the energy use on your DHW alternate daily heating cycle. 

A quick check might be to see what outdoor temperature your Heat Pump switches on to protect your pipework from freezing. This is part of the “Freeze Stat Function”.

Our factory setting for this function was when the outdoor ambient temperature was as high as 15C which meant it came on a lot if the time. We now have it set to 3C. (We don’t have glycol or it could be lower)

Freeze stat function is located in the “operation settings” menu

Main controller/ Menu Button/ Service Menu/ Operation Settings/ Freeze Stat Function 

Here you can see what the existing ambient is set at…. (the ambient can also be adjusted up or down.) 

Can you confirm if you are familiar with the service menu? And what setting you have if you can locate it? Also can you confirm what part of the country you are located?

Any other information on your setup would also help eg hp size house style etc.

Posted by: @tufty

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Ive just taken a reading from my Ecodan. I dont need heating, so put it on defrost mode on my handheld thermostat 8 week ago.

 

Hi I’ve just been reading a few of your earlier posts so I can see you’ve been getting familiar with quite a bit of your ecodan settings already. With earlier discussions.

I note from above comment you have switched to “defrost” with your hand held thermostat. I’m guessing you’re still using the Salus third party thermostat? I don’t think this will turn off or alter your room heating settings on the Ecodan -as far as I am aware. As I understand it you cannot operate in Auto Adaptive mode with the Salus thermostat.

so if your system is still operating in weather compensation or flow temperature mode the change to the thermostat won’t switch it off.

The simplest option to switch off the room heating while keeping the system active so you can boost the DHW is to:

open the right hand menu (button 4) and pick the house button until you get the 🚫 sign show on the House icon. That will prohibit the heating from coming on.

Apologies if you already know this but I hope this helps.

I’ll post a picture of what the home heating screen will look like:

the home heating icon is the third image 

Addendum

In your first comment you said:

“The Ecodan does say that its heating is prohibitive”. I think this is a slight misunderstanding in that the term PROHIBIT is used in their manual to describe stopping the heating or stopping the DHW etc. 

Thanks so much guys.

@SUNandAIR : Yes, its starting to come back to me now, last spring I probably did as youre saying: go into the Ecodan interface itself and turn off the heating. (I have a short memory! 🙄 )

Im away for a few days, back on tuesday, so Ill investigate further then. Many thanks.

Hi @tufty 

It was handy to skim read some of your earlier posts to learn what equipment your system is using and what kind of thermostat you had. I hope the suggestion is easy to follow and solves things for you.

Ive just turned off the heating on the Ecodan. I will check the readings in a few weeks and compare. Thanks!

It's handy that you can turn the heat pump off (CH that is) on the Mitsubishis. Our heat pump doesn't give you the option so we have to turn off all stats to stop calling for heat, which is a bit of a pain if temperatures do fluctuate in spring and autumn. 

On the Grant system you can either turn the ASHP controller off, but that also turns off the timed hot water boost. Or turn the 3rd party thermostat off, which is what I've done. The weather compensation characteristic will disable heating anyway if the outdoor temperature rises above 20degC, and from about 18degC upwards it turns the compressor off for extended periods due to minimum turn down of the unit being higher than heating load demand. It's pretty self-balancing to avoid overheating the house. In the cooler early morning, the ASHP will come on, but then cycle with long off periods during the day if the load demand is low. I found toward the end of the heating season this worked well, just taking the chill off in a morning, but not cooking the house come later in the day. It was very economical too. (Well it would be, with the compressor off!)

I've got the MMRS package and noticed Ecodan uses about 0.5-0.6kwh a day when idle (seen somewhere about 24 watts per hour which sounds about right). So you're looking at 15kwh a month just being on without any heating or hot water in addition