Welcome to the forum.  feel free to ask any questions.

I think you may need to explain your set up a bit more.  What are the 'heatmisers' doing exactly and what is their purpose; what have they got to do with DHW?  How is DHW set up on the ecodan controller?

At any given time you can either be doing space heating or dhw heating but not both.   Normally DHW 'takes priority' in the controller over space heating and you can either set it up on continuous reheat or on timed.  In continuous reheat mode it will reheat at any time of day when it drops a certain amount below the set temp, often 5-10C.  In timed mode it will only reheat at the set times and only if, at the start of those times, it has dropped by a certain amount below the set temp.  All this would normally be set up on the ecodan controller.

Assuming you take showers in the morning and evening then why not set the DHW to timed with a reheat period overnight and a reheat period say mid afternoon?  Depending on how much water you use you might not need the second reheat period.

If you are losing more than 0.5-1 degree per hour then your tank isnt 'well insulated'.  Here is mine, also 210l albeit the Vaillant one, on, it seems, a day when we used hardly any DHW (perhaps we were out).

@jamespa Thanks for prompt reply, the tank stays hot all day, all night and is well insulated.  The reheat on the Ecodan controller is set to reheat during the times we want, twice a a day, the heatmisers seem to control the pumps to send hot water to taps and shower.  The issue is when they're on they seemingly pump water around the house continuously  losing temp in a few hours......I could set the heatmiser for a few hours in the morning for us but when a child decides to shower outside that window no hot water is pumped to taps even if the tank has hot water.....does that make sense?

Having heatmiser timer on 24hrs just seems wasteful and acts like another form of underfloor heating!  But losing up to 10 degrees on switching pump on and defrost also seems wasteful.  Or is it just a feature of heatpump set-up?

Thanks,

Neil.

Posted by: @ngillam

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the heatmisers seem to control the pumps to send hot water to taps and shower.  The issue is when they're on they seemingly pump water around the house continuously  losing temp in a few hours..

Posted by: @ngillam

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Having heatmiser timer on 24hrs just seems wasteful and acts like another form of underfloor heating!  But losing up to 10 degrees on switching pump on and defrost also seems wasteful.  Or is it just a feature of heatpump set-up?

Ah, you have a water circulation loop, (like in hotels) which does exactly that, keeps water circulating round the house continuously so you can enjoy the benefit of instant how water 24*7 rather than having to wait a minute while it works its way through the pipes from the cylinder.  As you say its additional, inefficient, UFH in winter and unwanted heating in summer.  This is absolutely nothing to do with heat pump set up or indeed heat pumps, its a part of your plumbing design.  I didn't realise anyone fitted these in domestic dwellings, more normal is to design out the underlying problem by grouping together the water consuming rooms.  

Is the distance from DHW cylinder so large that you actually need this feature, or would it be better simply to bypass/remove the pump and let the water pressure do its job (assuming you have an unvented cylinder)?  It might be necessary to do some capping off also if you go down this route.  

I have heard of a control system for circulator loops where you measure the recirculating water temperature and only turn it on when it cools, and/or at certain hours of the day.  Therre may be other schemes - Im not an expert in circulating loop control systems though and there maybe nobody here who is.  The Buildhub thread on general plumbing or hot water cylinders might be your best bet - it really has got nothing to do with ASHPs,  so if you do post it elsewhere I suggest in a more general thread as it will likely get more responses.

@jamespa 

I have a DHW recirculation circuit in my house, the circulation pump was originally controlled by a conventional central heating time switch, programmed to fit in with our domestic routine. I swopped this timed switch for a "kinetic switch relay" controlled by a "kinetic switch" in the bathroom so that I was no longer tied to the programmer timings thereby giving more flexibility.

https://www.toolstation.com/culina-single-kinetic-push-switch-kit/p11484

The recirculation circuit on demand saves both water and also stored heat in the DHW cylinder.

@ubert767 

Interesting.  So the relay detects you are in the bathroom and switches the recirculation on?  If so how does this work for the other outlets?  Or do you have to switch it on manually?

If you do have to switch it manually what's the point, you still have to wait for the hot water to reach the taps just like you would with no loop.  What am I missing/misunderstanding?

@jamespa 

The relay is actuated by a wireless pulse generated by the kinetic switch, controlling the recirc. pump which is piped to all my sanitary hot water outlets. The relay can be triggered by multiple kinetic switches if desired. 

In my case it's not a time saving device, rather a water and energy saving device.

Posted by: @ubert767

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In my case it's not a time saving device, rather a water and energy saving device.

Sorry Im still not getting it. 

How does a recirculating loop with one or more switches save either water or energy relative to the simple arrangement, ie where the tank is connected by a single pipe tree and branch arrangement to the outlets, and the water pushed through the pipes (when you open a tap) by the pressure of the mains?

SOFAIK the whole point of a recirculating loop over a simple tree and branch system is to get instant hot water at the taps.  If you forgo that to save time and energy, surely you might as well forgo the whole loop idea in the first place?

Either Im missing something or this is technology to solve a problem created by technology, but the problem it solves wouldn't have existed if the technology hadn't been deployed in the first place.

Perhaps you could help me out by explaining what the advantage is of the system as you have it over the simple unpumped single pipe tree and branch arrangement that the vast majority of houses have?

Morning, and thanks for all the replies.  I suppose it's something I'll update in the future, I assume the water saving element mentioned is because you won't run off good water just waiting for the hot to come through.  Our house is spread out on one level with bathrooms at the end of each wing so the distance from tank to each outlet would create an amount of cold water run-off each day which would mount up........that's the only thing I can think of.

Thanks,

Neil.

Posted by: @ngillam

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I assume the water saving element mentioned is because you won't run off good water just waiting for the hot to come through.

Ah, got it.  Requires some discipline though if the pump is only triggered manually on demand, how many teenagers will have that?

@jamespa I tried to discuss with kids, I got a couple of eye rolls....and one tutted!

Posted by: @ngillam

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@jamespa I tried to discuss with kids, I got a couple of eye rolls....and one tutted!

Exactly.

It strikes me that grey water recovery might be a simpler and more robust way to 'save' the water.  There is still some heat lost though.  A smart tap that turns the pump on but then only turns the tap on when the water comes through hot is the ultimate solution.  Are we overthinking this problem?