A useable AS heat pump?

No, the immersion is usually brought in on a separate cycle. Most of them have that as part of the controls, or the old school installs can have a separate relay box and timer.

On ours there's a separate 'hot' stat - once the ASHP has got the tank up to temperature (eg 55C) the 'hot' stat closes and the immersion (set to the usual integral 60C stat) kicks in to bring it up to legionella-zapping temperature. If the tank hasn't already got up to temps the legionella immersion won't kick in, meaning you aren't running electric heat except for that last 5C. Currently the timer is set to fire that topup immersion once a week.

(there are tables that give you the frequency you should run it, from twice a week to once every 2 weeks - if you don't use much hot water so the water sits around, or someone in the house is immunologically compromised, you should run it more often)

Theo

It has a GWP of 1, compared with a GWP of 677 for R32, and 2088 for R410A. So you can breathe easy :-)

(a bigger problem is the R134A - GWP 1430 - in cars, which seem to perpetually leak given the number of regas services available. The R1234yf in newer cars has a GWP of 4, so that's better)

Theo

All bollocks since global warming isn't a problem and isn'tt happening very much and is beneficial where it is.

In a typical domestic environment is this a real problem? The chances are that no water becomes stagnated and the water in the tank is being replenished throughout the day, and every day, with chlorinated water from the mains.

It depends. Probably not in most cases. But:

Some people don't use a lot of water, so the tank doesn't get much replenishment. For example people who live alone, bathe once a week (or have an electric shower) and only use a little hot water in sinks the rest of the time.

Some people have weak immune systems (elderly, etc) and are more susceptible to pathogens. Other people smoke, and so likewise.

Since an installer can't know whether those things will apply, either at present or to future occupants, they need to put mitigations in place. A simple immersion boost is not a big ask.

Theo

Try traveling around some of the islands in the South Pacific and you will see the non-beneficial effect.

Like Canada, they don't have the gulf stream to keep them warm. If we had winters like theirs, our houses would be better insulated, but with mild winters people would rather spend excess income on holidaying in the sun and luxury living. Plus the hideous tendancy to have 'exposed brick and/or stone' inside 'character' properties.

Not if you have a copper tank. Copper is a wonderful biocide.

Can you remember the make ?

Yes South Georgia is much the same latitude as Manchester yet still seems to have snow capped mountains most of the year...

But that is the South Atlantic and quite near to Antarctica, not the South Pacific

Yes it is but the same Latitude doesn't have that the benefit of the gulf stream?...

It's labelled AirForce Climate Control. I suspect they're churned out of a Chinese factory, and this is the name B&Q asked to be put on the ones supplied to them. I've seen absolutely identical units with other names on them.

Mine is 12,000 BTU/Hr. They also did a 9,000 BTU/Hr version (looked identical), and I might have seen reference to a 15,000 BTU/Hr version but that was never stocked by my local B&Q.

I decoded the remote control, which means it's now driven by my home automation system. All the settings are stored/remembered by the remote control which seems silly, but actually made it very easy for a home automation system to take over that role. e.g. although the remote control has + and - buttons to increase and reduce temperature, it actually transmits the temperature required, not an increment or decrement message. Similarly, the remote has a button to toggle on/off, but it transmits on or off, not a toggle message.

Regards Andrew