That's an expensive belt @sheps

Not only is there the cost of the booster and its installation, but when it kicks in, the efficiency of the ASHP itself will be significantly reduced.

Assuming that booster is to run off standard-rate electricity, why couldn't you just plug in a fan heater instead?! 🤔 

@transparent Indeed. I am going to follow up on that as well. Its a steep learning curve.

Posted by: @sheps

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@kev-m From the heat loss report. It seems the booster is just belt and braces?
when external temp is -3.8c , total heat source to heat must provide 11.84kw. Max designed Flow temp 50 c SPF 3.92 and “heat ump can run happily at 55c giving a fair margin of safety on  the output plus the 3kw booster heater on top of this again, “

@Shep, having a booster isn't necessarily a problem as some ASHPs (e.g. some Daikin models) seem to come with one as standard.  I would be more concerned that your heat loss (assuming it's correct) is very close to the nominal output of your quoted ASHP.  What make and model has been quoted?  Some ASHPs, even under test conditions, can't deliver their nominal (badged) output at cold ambient temperatures.  Also, all ASHPs suffer from frosting up at lower (below about 3 deg C) temperatures, and defrosting reduces output further, by (in my experience) 10-15%. It's possible that on a cold winter's day your booster may have to be used more that you'd like. OTOH you're not going to experience your -3.8 design temp very often.  

Hi all, Gerry here. Located on the east coast of Ireland. I have a:

. 4.2 kWh PV system (SE facing)

. 40 kWh Nissan Leaf 

. newly-installed 10 kWh Viessmann heat pump

Pv export tariffs are decent here atm, but am interested in all things battery and PV and how to run my HP most efficiently!

Hi @GC61 Welcome to the Forum! I’ve also recently had my ASHP installed (only the second Panasonic on the list it seems!) and can’t wait to see how it runs over winter on the battery either. If you’ve got any specific questions/train of thought then feel free to start a new topic. Nothing we (I) love more than an excuse to chat renewables 😁

@gc61 - Does the installation of a high quality (expensive) Viessmann HP mean that you get an equally high quality installation from a Viessmann-trained company?

You will note that this forum is littered with reports of poor-quality installation and system design, which then lower the efficiency to unacceptably poor levels.
For example, how good is the pipe insulation on your new unit?

@transparent Having done some research on different HPs and manufacturers, I decided I wanted a Viessmann unit. However, the number of accredited installers was very limited. I eventually found someone who was fully Viessmann trained and who had made several visits to Germany for further installation advice and guidance. I also checked out online reviews and testimonials of his work prior to signing a contract. The HP was installed in May and so far, so good. Obviously, to date, I have not been using space heating, only DHW, so winter will be interesting! I'm no expert, and have nothing to compare it to, but the insulation does look quite good. Ultimately though, I suspect getting a proper installer who knows what they're doing is more important than the actual unit.

That's the response I expected from a Viessmann customer.
They've established a niche market at the high quality end of the spectrum.

I doubt that Viessmann would tolerate the poor level of installation work which many companies exhibit,
and for that reason there are fewer to choose from.

Any chance of a photo or two?

@transparent

Hope this is useful. (Note to self: clear weeds and paint gate!)

Posted by: @gc61

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(Note to self: clear weeds and paint gate!)

I remember when I first put my hand on a digital camera 20 years ago, "everything" looked in need of a touch.

Not a photo which screams out "well insulated pipework" @gc61 🤔 

Equally, whilst Viessmann could use your third photo for advertising purposes, on this forum we'd be more interested in seeing what's behind the outside unit.

What's the external insulation like,
and how has the installer arranged for the pipes to pass through the wall?

Posted by: @transparent

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whilst Viessmann could use your third photo for advertising purposes

Not until @gc61 clears the weeds and paints the gates.

I can’t quite make out the third photo. The front of the mounting frame appears to be supported level on chunks of old drive way blocks and resting on what appears to be tarmac, while the rear might be bolted to a concrete path. Could there be an issue with noise/vibration and settlement?