Mixing tank temp shows 25C when not connected, I believe.  Certainly mine does.

I did think about getting a separate temp probe from Mitsi to install in the buffer tank, but then I also had mine converted to a volumiser and so it is at the flow temp and no need for an additional sensor.

BTW post conversion my Ecodan is running with zero cycling and currently only pausing for the defrost cycles.

Posted by: @davidalgarve

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MelCloud gives"Tank Temperature", which appears to be the DHW tank, but in addition it provides data for "Mixing Tank Temperature".

The latter doesn't seem to vary much from 25C, so what is this connected to and can it be more usefully employed?

Similarly, "Set Tank Temperature" doesn't very often

Hi Dave, the set tank temperature shows the temperature your DHW is set at. So it stays at a fixed temperature and doesn’t vary. you can then compare the actual tank temperature which does vary as hot water is used.

The mixing tank temperature is unused except in sutuations where a mixing tank is used.

useful tip

I switch on the Mixing Tank and the Set Tank on my MELCloud graphs because they create a display field that is of a constant graph scale. In other words it’s easier to compare graphs if they appear at the same scale. See attached examples… one shows 5degC scale while the other shows a massive scale change because the horizontal graph lines have been removed.

So when viewing subtle differences in delta T or flow temperature it’s handy to keep to identical display scales…. Hope this is useful 👍

Posted by: @downfield

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I also had mine converted to a volumiser and so it is at the flow temp and no need for an additional sensor.

Hi downfield,

Sounds like you’ve got a result with the volumiser….. I’m curious about where you installed the volumiser…. From the above description did you install it on the flow side…..? And was it after the 3 port valve? Also what volume was the buffer? 

TIA

Yes very pleased with the change from buffer to volumiser.

Andrew Millward (Watford based) did the work and advised fitting on the flow side, which seems to work.  My "logic" for this is that on a defrost cycle the HP uses warm water from the returning flow and so the volumiser has plenty of warm water to send into the house.

Volumiser is 100 litre capacity.

My Ecodan is oversized at 14kW - heat loss during the recent cold snap was about 8.5kW at 0C outside temp.

So I was surprised there was only one cycle every 75 mins even when the temps were 12 - 15C

@sunandair Hi Sun and Air. I am not sure I understand this:

"the set tank temperature shows the temperature your DHW is set at. So it stays at a fixed temperature and doesn’t vary. you can then compare the actual tank temperature which does vary as hot water is used"

My DHW is set for 52C.

I am attaching a similar screenshot to yours at 11:00 this morning

However, I am on a trial with Havenwise so maybe they are changing figures. e.g. the "Set temperature" for room heating on my Mitsu wireless controller is currently reading 29.5C when the required room temperature on the Havenwise app is 22C

Posted by: @davidalgarve

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@sunandair Hi Sun and Air. I am not sure I understand this:

"the set tank temperature shows the temperature your DHW is set at. So it stays at a fixed temperature and doesn’t vary. you can then compare the actual tank temperature which does vary as hot water is used"

My DHW is set for 52C.

I am attaching a similar screenshot to yours at 11:00 this morning

However, I am on a trial with Havenwise so maybe they are changing figures. e.g. the "Set temperature" for room heating on my Mitsu wireless controller is currently reading 29.5C when the required room temperature on the Havenwise app is 22C

It's a good tip, actually, @davidalgarve. All @sunandair is saying is that the Melcloud app adapts the Y axis scale to fit the data points. That's great if you want to magnify any variation but if you're wanting to look at a graph that uses a consistent scale over weeks, months or perhaps even years then adding the set mixing tank temperature (which doesn't change) as another series effectively standardises the Y axis scale for every time period you want to look at. 

Posted by: @davidalgarve

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However, I am on a trial with Havenwise so maybe they are changing figures. e.g. the "Set temperature" for room heating on my Mitsu wireless controller is currently

Yes it may be that your setup has changed the “set tank temp” output and used it for something else or it’s simply not being used which is why it appears at a low temperature default setting. What I do know is that our set DHW target temperature corresponds to this label. Anyway hopefully you get the idea. These bar lines can help to control the scale of the display just a small observation that may help.

Posted by: @davidalgarve

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However, I am on a trial with Havenwise so maybe they are changing figures. e.g. the "Set temperature" for room heating on my Mitsu wireless controller is currently reading 29.5C when the required room temperature on the Havenwise app is 22C

@davidalgarve

How is your trial going?  I am also on the initial trial and, whilst it hasn't quite been a week yet and it is very cold here, all of my COP figures on the Havenwise app (Total, Heating and Hot Water) have gone down, where I had hoped they would increase. 

Posted by: @davidalgarve

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@sunandair Hi Sun and Air. I am not sure I understand this:

"the set tank temperature shows the temperature your DHW is set at. So it stays at a fixed temperature and doesn’t vary. you can then compare the actual tank temperature which does vary as hot water is used"

My DHW is set for 52C.

I am attaching a similar screenshot to yours at 11:00 this morning

However, I am on a trial with Havenwise so maybe they are changing figures. e.g. the "Set temperature" for room heating on my Mitsu wireless controller is currently reading 29.5C when the required room temperature on the Havenwise app is 22C

This is Havenwise moving the MelCloud settings so that they don't interfere with their system instructions.  Room temperature is set to maximum (29.5) and DHW will be at 10°C until the times when you've called for a scheduled re-heat, at which point it will change until the re-heat has been completed.  The setting at 10°C then prevents the hysteresis re-heating kicking in.

I've learned this from my time having Havenwise run my system, so I'm used to both now.  I also have a mixing tank temperature at a flat 25°C, which is due to this not being in use on my system.

@morgan Hi Morgan.

I am struggling to keep the faith. More than a week passed and the system was learning nothing, at which point I was told that a Shelly H & T would be better than the Mitsu Wireless Controller, which had previously been said to be required.

Eventually after I decided to move the wireless controller to the coldest room in the house (our bedroom, downstairs) we saw some progress, but the target temperature of 22C was rarely met and flow temp was not as high as it might be. After buying more Shelly H & T's to spread around the house, I have chosen another downstairs room to position the wireless controller. So we are back into a learning phase and not so warm.

In addition, like you, I am getting significantly lower COP figures than previously and that is after changing the buffer tank to volumiser and deleting a pump.

I would like some relevant data to see why the disappointing performance, hence an interest in MelPump, but I can't say that I welcome using this in talking to Havenwise 

@sheriff-fatman Thank you.

That all makes more sense! The MelCloud data is already far from ideal and it is a pity that Havenwise can't find a way of controlling without having to make the "Set temperature" figure irrelevant for both room heating and DHW.