Posted by: @cathoderay

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[...] it is just there in case the heat pump packs up, as a backup to provide domestic hot water.

An immersion heater can always be disconnected or isolated at a later date if @cathyem1 wants to.

But I think there should be an immersion heater driven by the heat-pump when it's first commissioned.
Running anti-legionella cycle should be listed on the commissioning sheet.

Also, if it is operated manually or by a time-clock, then the regulations state that it must now have a red light just outside the cupboard to show when it's on.

Even if the electricity supply via the time clock was there prior to the heat-pump being fitted, the immersion heater still forms part of the new DHW system.
So a red warning light must be fitted.
If not, then the installation shouldn't be given a Building Regs Part-P certificate.

Posted by: @transparent

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But I think there should be an immersion heater driven by the heat-pump when it's first commissioned.
Running anti-legionella cycle should be listed on the commissioning sheet.

Also, if it is operated manually or by a time-clock, then the regulations state that it must now have a red light just outside the cupboard to show when it's on.

It seems Freedom have different ideas. Midea units do have something called DISINFECT but it gets turned off and an external timer and immersion heater are used instead. Here's a copy of three relevant pages from one of the many Freedom Heat Pump Quick Installation Manuals (available here): 

As I said, I just choose not to use the timer/immersion heater for anti-Legionella cycles. But it is clear from the above that Freedom intend the timer and IH to do the anti-Legionella cycle, and it is possible Baxi just follow the Freedom way of doing things.  

@transparent I will post more photos, but not today. I'll take some tomorrow and pop them on.

@cathoderay I seem to recall the installer mentioning the timer was there to kick in higher water temperature for the anti-Legionella cycle. It’s set for 01:00 once a fortnight.

Posted by: @cathyem1

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I seem to recall the installer mentioning the timer was there to kick in higher water temperature for the anti-Legionella cycle. It’s set for 01:00 once a fortnight.

Yes, it seems like it is set up Freedom's way. Freedom Heat Pumps are, or at least were, things may have changed, the main UK importer and supplier of Midea heat pumps, to the extent that in effect they were 'Midea UK'.  

Just make sure no one half asleep washes their face/hands at around 01:30 on the day the cycle runs! 

@cathoderay Good point! Thank you

@cathoderay Hi, can I boost the hot water temperature. My bath was lukewarm. 🥶

Posted by: @cathyem1

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can I boost the hot water temperature. My bath was lukewarm

Yes, and I don't think that counts as meddling!

On the main display, the right hand panel is about the DHW. When you first look at it (without pressing any buttons), it shows the current DHW tank water temperature. It will fall slowly over time as the tank cools, faster if you use hot water eg have a bath.

If you unlock the panel (bottom right button) and then use the arrows to select the right hand number, as you have done is this image you posted earlier: 

it will show the set domestic hot water temperature, ie what it will be heated to when the heat pump goes into domestic hot water heating mode. In the image is is set to heat it to 50 degrees (an OK setting). If you ever want to change it, use the up and down arrows and then press the centre 'return' button.

You also need to have the DHW heating on (enabled). This can either be whenever the DHW tank temperature drops below the set temp by so many degrees (default is 5 degrees, so with a set temp of 50, it would start heating the DHW when it drops to 45 degrees) or on a timer and temp has also dropped by the set amount. Since DHW defaults to taking precedence over space heating, I have the latter (set to come on between daily between 1300 and 1400), which also takes advantage of the fact this is usually a warmer part of the day.

For now, to keep things simple, I suggest you just make sure DHW heating is on (you can set up a timer if you want one in due course). The unit should default to DHW always on, ie whenever the DHW temp falls by the set amount, the DHW heating turns on. Once the DHW reaches the desired (set) temperature, the unit will go back to space heating. You can see this indirectly by (a) the tank actual temp being in a sensible range and (b) the centre panel showing a tap when it is in DHW heating mode (the other 'sun' symbol means it is in space heating mode). If this doesn't happen, you can manually override the DHW 'on/off' by selecting the hot water tank temp (middle of right panel, exactly as shown in the image above) and then pressing the on/off button at top right on the keypad, and 'squiggles' will appear next to the small tap symbol in the upper right hand panel. If the DHW temp is low, it should start to reheat it (tap appears on centre panel), and then revert to space heating ('sun' on centre panel) once the DHW has reached the set temp (50 degrees).

I have to confess I find the display rather confusing at times, but I think the above describes the essentials... The acid test of course is what the DHW tank temperature is. If it warms up when it should to the right temperature then it is working. 

Let us know how you get on!      

Posted by: @cathoderay

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In the image it is set to heat it to 50 degrees (an OK setting). If you ever want to change it, use the up and down arrows and then press the centre 'return' button.

I agree.

50°C is perfectly adequate for your DHW tank.

1: If you ask the heat-pump to take it higher than this, then it's becoming less efficient (costs more to run).
    You're approaching the point where you might as well have switched on the immersion heater 😯 

2: You shouldn't be getting a lukewarm bath if the tank temperature is 50°C.
    Did you use hot water for something else shortly before filling the bath?
    Is the hot water pipework to the bath properly insulated?

3: For comparison purposes, when anti-scalding mixer-valves are installed in hotels and nursing homes, their default output is set to 42°C
    So you're already well above that.

I have a thermostatic mixer valve in the top compartment of my DHW cylinder.

@cathoderay Thank you I have printed off your reply. 56 and very old skool 👵

@transparent Something happened last night that took us by surprise. Hot water disappeared, our kitchen sink cold tap stopped, and we couldn't flush our toilets 🤷‍♀️

Called the installer today and it turns out a valve was turned off which caused our water softener to have a meltdown when it tried to regenerate. As soon as the valve was opened the water softener did what it had to and lo and behold our cold water reappeared in the sink. This is all a bit of a rollercoaster 

@transparent The immersion went in this morning unfortunately 😳 as the installer suggested it to boost the DHW (see, I'm getting the lingo!)