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Mitsubishi 8.5kw ecodan


Taff

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Just reopening thus thread somewhat. 

 

I have been planning on the 8.5kW Ecodan unit, paired with their pre-plumbed cylinder, for some time. I had thought I can get that with the 300L but seems I can't. Only seems to be the 11.2kW or 14kW units with the 300L. I had done the the infamous calcs for heat input and I 'think' it says I only need 6kW max heat input (If i have read it right). 250 sq/m SIPS build.

 

Hence - the 8.5 would be ideal, but if I get the 11.2kW it's not the end of the world, slightly more expensive. But would it run less efficiently?. 

 

the main thing here is - I want 300L DHW storage.

 

thanks 

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6 minutes ago, PeterW said:

11.2Kw will modulate sown and run fine - will be under less stress. 

Thanks Peter I thought thst would be the case. 

 

Interestingly I just noticed @Stones you have a 8.5kW with the 300L (I'm sure I'd read that before on your blog but forgot). I was sure id seen that pairing for sale on numerous places but now seems to be the 300l offered with the 11.2 and 14 only ( admittedly I havent tried really realy hard to find someone selling that combo). 

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My local installer was happy to quote supply and install for the 8.5kW with matched Ecodan 300L tank. That was his default suggestion, in fact.

In the end I switched it out for the OSO Geocoil tank which actually reduced the quote and also reduces standing heat losses. 

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just contacted Mitsubishi uk and they have stated that your correct. The standard 300L would need a minimum of 11kw. He mentioned that the solar tank could be run with the 8.5kw. 

 

I’m sure there’s folk on here running an 8.5kw with a standard 300ltr! I may be wrong

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On 02/07/2020 at 05:50, JamesP said:
  • We have the following in our new self build. MITSUBISHI ECODAN PUHZ-W85VAA with a 300 Litres PRE PLUMBED EHPT30X  cylinder. Supplied 2019.

How you finding this, is it functioning as predicted?

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14 minutes ago, Taff said:

just contacted Mitsubishi uk and they have stated that your correct. The standard 300L would need a minimum of 11kw. He mentioned that the solar tank could be run with the 8.5kw. 

 

I’m sure there’s folk on here running an 8.5kw with a standard 300ltr! I may be wrong

hmmm... I wonder if thats something they have recently recognised and why they've done that. I suppose the solar would have a bigger heat exchanger which makes sense. 

 

But I haven't read anyone on here having issues. With 8.5kW ans 300l  standard pairing. 

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54 minutes ago, Taff said:

just contacted Mitsubishi uk and they have stated that your correct. The standard 300L would need a minimum of 11kw. He mentioned that the solar tank could be run with the 8.5kw. 

 

I’m sure there’s folk on here running an 8.5kw with a standard 300ltr! I may be wrong

I am running a (different make) 5kW ASHP with a 300L tank.

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1 hour ago, Taff said:

How you finding this, is it functioning as predicted?

It has only been in use since Feb 2020 so I have limited experience. Not noticed any issues so far. It has just been left to run when required, not timed.

It has a n Eddi PV diverter fitted so during May and June it used 4 kWh a day for hot water. In March it used 6.6 kWh per day. Family of 4,  so 4-6 showers a day, occasional bath and washing up.

It is very quiet compared to a NIBE.

What @PeterW mentioned early is a good point.

 

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On 02/07/2020 at 05:50, JamesP said:
  • We have the following in our new self build. MITSUBISHI ECODAN PUHZ-W85VAA with a 300 Litres PRE PLUMBED EHPT30X  cylinder. Supplied 2019.

How you finding this, is it functioning as predicted?

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On 02/07/2020 at 05:50, JamesP said:
  • We have the following in our new self build. MITSUBISHI ECODAN PUHZ-W85VAA with a 300 Litres PRE PLUMBED EHPT30X  cylinder. Supplied 2019.

How you finding this, is it functioning as predicted?

 

dont know why it keeps attaching @Jamesp post, cannot get rid of it. What chance have I got running something complicated!

 

Just spoken the to the people supplying ours, he said all the calculations work out and it would be fine. The only advantages would be higher flow rates and quicker recovery time for the hot water. 

 

To be safe I’ve opted to upgrade to the 11kw it was an extra 900. Just told the misses to cancel the curtains ?

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@Taff

Have to wait a year to really understand how well it performs in all weather conditions.

It just works very well so far. Many others on the Forum have the same product.

Edited by JamesP
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On 02/07/2020 at 00:00, PeterW said:

11.2Kw will modulate sown and run fine - will be under less stress. 

 

Slightly different situation, but a near-neighbour installed a 14kW split system Ecodan and when it's driving the UFH he finds it can't modulate low enough so is constantly short-cycling, and only achieving COP of 2 or less. He's working on a claim under MCS to get it replaced as it's over specified for the property. So while oversizing is fine for heating a cylinder, also check it won't be too much for the heating circuit.

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11 minutes ago, joth said:

 

Slightly different situation, but a near-neighbour installed a 14kW split system Ecodan and when it's driving the UFH he finds it can't modulate low enough so is constantly short-cycling, and only achieving COP of 2 or less. He's working on a claim under MCS to get it replaced as it's over specified for the property. So while oversizing is fine for heating a cylinder, also check it won't be too much for the heating circuit.

Very good point. My little 5kW unit does a good job of heating the house. Imagine how over specifiec a 14kW one would have been.

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16 hours ago, joth said:

 

Slightly different situation, but a near-neighbour installed a 14kW split system Ecodan and when it's driving the UFH he finds it can't modulate low enough so is constantly short-cycling, and only achieving COP of 2 or less. He's working on a claim under MCS to get it replaced as it's over specified for the property. So while oversizing is fine for heating a cylinder, also check it won't be too much for the heating circuit.

Split units are a totally different beast to a monoblock, so everyone should keep that in mind and take that with a pinch ;).... Does show that the MCS scheme is good for that type of instance, but hard to understand how that ever became a problem because being an accredited MCS installer ordains you to do due diligence, way before executing the installation. Perhaps that particular install is simply missing a buffer tank.

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16 hours ago, ProDave said:

Very good point. My little 5kW unit does a good job of heating the house. Imagine how over specifiec a 14kW one would have been.

Does it 'max out' when reheating the cylinder Dave? Whats the noise level in DHW mode is my point, with 5kw vs 300L?

Edited by Nickfromwales
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11 minutes ago, Nickfromwales said:

Does it 'max out' when reheating the cylinder Dave? Whats the noise level in DHW mode is my point, with 5kw vs 300L?

Yes when heating DHW the HP runs at full tilt most of the time, unlike when heating the house the compressor and fan runs much slower.  The HP is just outside a small living room window and that is the only time we can hear it at all inside.

 

The default with mine is to only run in DHW mode for half an hour at a time (you can change that)  I speculate that is either to reduce risk of icing, or the designers were worried if the space heating was off for more than half an hour at a time you might notice it (you would not in our house)

 

A typical day when you are only re heating what has been used it will get the tank up to temperature in one half hour cycle, but if the ladies have both had a "hair wash" shower, or a bath, it will take longer.

 

This week, which has been a pretty grey and quite wet week, so poor solar PV generation, we used 15kWh heating DHW with the heat pump.

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38 minutes ago, Nickfromwales said:

Split units are a totally different beast to a monoblock

Can they modulate down any further though?

 

37 minutes ago, Nickfromwales said:

Perhaps that particular install is simply missing a buffer tank.

Is that not just introducing more heat loss into the house.

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1 minute ago, MikeSharp01 said:

Can they modulate down any further though?

That's my understanding, yes. 

 

2 minutes ago, MikeSharp01 said:

Is that not just introducing more heat loss into the house.

Not really as the buffer would only be inline with space heating and not the DHW, so adventitious heat given off by that vs nuisance heat. Very difficult to offer more to that post as we do not have client / dwelling specific parameters to hand.   

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