In the summer, can a heat pump do cooling *and* hot water?

[Garald]

It seems my search is converging to a Mitsubishi reversible ASHP with its own water heater ("Duo"). (Reversibility is nice - we'll be able to circulate cold water around the PIV module.)

 

Question: will there be any obvious issues during the summer, when the heat pump will have to switch between its ECS task and producing cold water for its cooling function? (Potentially useful information: it will use only a tiny proportion of its cooling capabilities - less than 1kW.)

[nod]

The sellers I’ve spoken to all advise Against it 

[jack]

1 hour ago, nod said:

The sellers I’ve spoken to all advise Against it 

 

Why do manufacturers offer cooling mode if it shouldn't be used?

 

As long as you take care to avoid condensation issues, there's no good reason to avoid cooling mode. I've run mine to cool our slab during summer for several years without issue.

 

7 hours ago, Garald said:

Question: will there be any obvious issues during the summer, when the heat pump will have to switch between its ECS task and producing cold water for its cooling function? 

 

Is ECS hot water production and is a "PIV module" a radiator type module that you blow air across for cooling?

 

Depending on how your valves are set up, you might get a slug of hot or cold water escaping into the wrong circuit as it changes mode, but that's unlikely to make any practical difference.

 

The main thing with cooling is condensation risk. If you're using a radiator-type attachment to cool air, you'll generate quite a bit of condensation. You'll therefore need to be sure that the cooler has a drain for capturing condensation, and you need to be able to plumb in somewhere for the captured condensation to go 

[akjos]

For the heat pump itself it’s no issue at all to switch between heating and cooling as much as you like.

That’s exactly what it does during defrost in winter constantly. It switches to cooling and runs hot gas outside to melt frost on the coils, then back to heating.

 

As @jack mentioned, you have to pay attention inside where you might have condensation. But if you use fan coil units for cooling, those usually have their own condensate drain.

[nod]

1 hour ago, jack said:

 

Why do manufacturers offer cooling mode if it shouldn't be used?

 

As long as you take care to avoid condensation issues, there's no good reason to avoid cooling mode. I've run mine to cool our slab during summer for several years without issue.

 

 

Is ECS hot water production and is a "PIV module" a radiator type module that you blow air across for cooling?

 

Depending on how your valves are set up, you might get a slug of hot or cold water escaping into the wrong circuit as it changes mode, but that's unlikely to make any practical difference.

 

The main thing with cooling is condensation risk. If you're using a radiator-type attachment to cool air, you'll generate quite a bit of condensation. You'll therefore need to be sure that the cooler has a drain for capturing condensation, and you need to be able to plumb in somewhere for the captured condensation to go 

The suppliers I spoke to said it voided your grant 

But as you say Why The option 

Probably similar to MVR More environmentally friendly to open a window than use a tiny amount of electricity 

[Garald]

1 hour ago, jack said:

 

 

Is ECS hot water production and is a "PIV module" a radiator type module that you blow air across for cooling?

 

Yes, exactly. Sorry! Late-night failure of translation module in the brain! ECS = DHW.

 

The module is Hydro'R Aquarea, something designed by Panasonic. Installers are a bit scared about using it with non-Panasonic heat pumps, but I don't see the issue.

 

1 hour ago, jack said:

 

The main thing with cooling is condensation risk. If you're using a radiator-type attachment to cool air, you'll generate quite a bit of condensation. You'll therefore need to be sure that the cooler has a drain for capturing condensation, and you need to be able to plumb in somewhere for the captured condensation to go 

 

Hopefully the module is properly designed!

 

https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.vmi-technologies.ie/wp-content/uploads/2021/03/EN-Catalogue-VMI%C2%AE-2021.pdf&ved=2ahUKEwjhjK6xwvv8AhXOh_0HHQWGAh4QFnoECBsQAQ&usg=AOvVaw0LXu1ytQzrm1W_PM3MkJAp

[jack]

43 minutes ago, nod said:

The suppliers I spoke to said it voided your grant 

But as you say Why The option 

Probably similar to MVR More environmentally friendly to open a window than use a tiny amount of electricity 

 

I can't remember whether the rule changed or just the interpretation of the rule, but there used to be a belief/fear that you couldn't get the RHI if cooling was enabled. ASHPs were supplied with cooling mode disabled by default, and you had to enter a code or change a setting to re-enable it.

 

I believe (but might be wrong) that those fears proved unfounded, or perhaps the rules changed. Either way, it was always easy enough to get around.

 

Opening a window only works when it's cooler outside than in. I tend to only use cooling mode when we have a run of very hot days, as it takes that long for the house to heat up significantly. Also, we have a lot of solar, so it doesn't cost anything to have the cooling on when we choose to use it.