There will be others, @notechknowhow, who may well be able to comment helpfully and knowledgeably in ways that might get you headed in the right direction to start with, but could you just let us know which part of the country you're in? It seems to me that a service that's actually effective might be a good thing to get done anyway and if we know whereabouts then there may be a member who can recommend a heat pump installation and maintenance company near you. You might also want to let us know which brand of heat pump too since even if it's forum members who help then they'll need to know that at least.

@notechknowhow

generally the answer to should you ASHP heat your hot water is yes. However that said mine doesn’t and isn’t connected to my cylinder for good reason. 

if your cylinder is connected to your ASHP pipe work then it should be capable of heating but might just not be scheduled to do so. Perhaps the Eddi was providing all the hot water needs. I would look to see what schedule is set up for hot water on your heat pump controller, before paying anyone to come and look at it. 

That's a pain, sounds like you might have been paying through the nose to heat your hot water for a while using the immersion heater. 

To help with troubleshooting we usually also ask for the make of heat pump, hot water cylinder and perhaps a photo of the setup of the cylinder and around it, in case it  matches one that people have seen already. 

Do you have any manuals?  If you have no tech know how, going through menus can be worrying, but is the easiest way to try and find out what is happening, but unless we know what kind of control box you have, we can't really advise. 

Posted by: @notechknowhow

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Should the ASHP be generating hot water despite the eddi being off? 

Yes, definitely. As @guthrie has said, please can you share your ASHP brand/make. It may be a settings issue. 

Posted by: @notechknowhow

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Acquired a PV and ASHP system as a result of a house purchase. Nothing was explained and I am gaining understanding bit by bit on how it all works. 

We had a routine maintenance check done last year, the engineer spent most of his time on the phone asking for advice on what he was looking at. We noticed after he left that the hot water never seemed to work as it did before. 

This week the myenergi eddi kept tripping whenever it directed power (boost or PV) to the immersion cylinder (unvented dual cylinder). Electrician diagnosed issue which was a very small water leak in the immersion heater element which was causing the terminals to short circuit the system. We have turned the eddi off.

Once the eddi was off we noticed we had no hot water at all (none for three days so far while waiting for the new immersion element) and now (not fully understanding the system) wonder why the ASH is not generating hot water in the cylinder?  Is that a genuine concern? Should the ASHP be generating hot water despite the eddi being off? 

We are hoping a solution may all explain why our hot water has been 'odd' since the maintenance check last year. Be great to have it all up and working again.

This does sound like a settings issue, or just possibly a diverter valve issue to me.  And suspiciously it sounds like your 'maintenance check' is probably the cause of the problem!

The first thing to bear in mind is that the eddi and HP are essentially independent ways of heating water.  Of course the eddi only works when its sunny and the HP only works if its scheduled to do so.  Most likely the only feedback between the two will be their respective thermostats.

With that basic knowledge (unless you have a strange setup) you can start to ask some questions to diagnose.

If its sunny for several hours does the water heat up.  If so the eddi is probably OK  - unless the sunny period by chance is combined with when the HP is scheduled to heat.  There should also be some indicator lights on the eddi which will help

During the winter period  (but after the maintenance check) did the water heat up.  If so the HP is at least capable of heating the water.

If the answer to the second is no then, does the HP scheduler have a time for hot water, when, how long, to what temperature?  Also does it have a legionella cycle

Staring with the answers to these questions and the make/model of heat pump it should be possible to diagnose 

If you can share some more observations that would help.

@jamespa et al 

Overwhelmed - Thank you all for your responses - I can see I need to provide more information which I will do later this morning when back from plumbers merchant. 

But to answer the immediate Q - During the winter (which knows no end) we had to use the scheduled / manual boost on the eddi to generate hot water - so I feel that is a significant observation given what James and you have all suggested. Waiting for an engineer to replace the leaky immersion element this afternoon so unable to have the eddi on at all. However, I can say the whole time the eddi has been out of action over the last three days there has been no hot water generated.

Well that tells us that the Eddi works in manual mode (but may or may not work in divert mode) and your hp isn't heating water at all.

So now the question becomes - is your hp actually scheduled to heat the hot water or is there something wrong.  You should be able to find out the answer to the first by looking at the hp controller.

Also on a sunny day do you now get hot water (which will tell us if Eddi works in divert mode or not)

@majordennisbloodnok 

Hi there I tried to upload several photos try again here 

There is also a Tesla wall, myenergi harvi and eddi  

The Ferroli Delta Sol BS - I understand was the original thermal solar system at the property. It is attached to two very large solar panels - this is switched off but also is apparently disconnected internally and I do not know if it is possible to get working again. The heating engineer who ran his eye over it said he didn't have the knowledge to do the electrics (reconnections). To your other Q we are based in Cornwall just outside Truro. 

@jamespa 

I have now posted some photos of the equipment. I am pretty sure the eddi worked in divert mode as I was watching it divert when testing the fuse box to see what was causing the trip. The eddi divert switched to heating mode before triggering the circuit trip. 

When the sun is shining the hot tap water is notably / exceptionally hot. 

Having come from a house with a gas combi-boiler I did not understand the system I inherited and thought that the ASH was for the underfloor heating only and the solar was for the hot water, and that when there was no sun the system simply drew on the mains supply. (Doh!) Have learnt a great deal just from the comments made by all here. 

Not knowing the ASH we assumed the issue with the HW was with the solar alone. We did know there was a change following the maintenance inspection. Now you have all drawn attention to the lack of hot water when the eddi is off I understand where the issue lies.

I clearly need to learn how to operate the Daikin ASH controls