Switching ASHP to cooling

[Tom]

Hi All - we had our Ecodan ASHP installed last year and only really used it in anger from December when we moved in to the house. It's been unused since March/April. I asked the installers recently how we could switch it to cooling, as it would be nice to have the option to cool in the bedrooms (over the heatwaves this summer temps have gone up to ~25deg), but after trying to brush me off with "the unit is not set up to do that" they have finally come back with this: "The pipework wouldn't have been insulated sufficiently to deal with cooling. Therefore, the buildup of condensation may cause further issues. To mitigate this, we would need to add a heat exchanger/cooling exchanger directly after the primary pipework, which would mean adapting the primary pipe work. "

 

Does that make sense? Surely it's got to be simpler than that? If there might be an issue with condensation then a few of the pipes might need to be lagged perhaps (which, tbh, they should be anyway to reduce heat loss when heating) - but a heat exchanger?

Any advice gratefully received!

[JohnMo]

1 minute ago, Tom said:

Does that make sense?

No

 

To change over from heat to cool varies between makes and models. Some ASHP do not do cooling, so you need to cross reference your model number, to see if it does. Some manufacturers want to sell more kit to allow cooling others don't. But you normally need a zero volt trigger to make the switch, I currently use an old single pole light switch, repurposed.

 

Actual cooling. Radiators do not work in cooling mode.

 

UFH does. You would generally operate at a temperature above dew point, which is generally above 12.5 degs. If your heat pump runs long compressor cycles better to run closer to 16 Deg flow temp. Running at 16 you don't need any insulation.

 

 

[Tom]

Thanks @JohnMo, we're 100% UFH so all good. I'll track down the model number this evening and look it up. What do you mean by "long compressor cycles" - and how would I know?

[JohnMo]

37 minutes ago, Tom said:

What do you mean by "long compressor cycles" - and how would I know?

How many times the heat pump cycles on off when asked to do work. The better sized your heat pump to demand the less it will cycle, mine is double the size it needs to be so runs for 10 to 12mins every 30 mins to an hour. 

 

So if you run 40 to 50 mins still to a temperature closer to 16.

 

This is mine running the other day, the light blow highlights are the actual heat pump compressor doing work, the gaps in-between are it resting between cycles.

 

Easy way is if the fan is running your compressor is running, if off it's not.

 

Just had a thought, if you have thermostats you will have to wind them up to max temperature to have a demand to heat, even though you are cooling. Also if you have volumiser or buffer, need to make sure they are only in the UFH circuit.

[Nick Laslett]

39 minutes ago, Tom said:

Thanks @JohnMo, we're 100% UFH so all good. I'll track down the model number this evening and look it up. What do you mean by "long compressor cycles" - and how would I know?

Here is a video from John Cantor talking about ASHP cycling in great detail. Might be too geeky.
 

 

[Tom]

Ah sorry, yes, cycling - gotcha. We have no buffer but a lot of pipework and thick concrete and screed to suck heat (and lose heat I guess) - so generally cycles tend to be long. We do have a low loss header if that affects things? 

[JohnMo]

1 hour ago, Tom said:

We do have a low loss header if that affects things? 

The plague of heat pump installs, like a buffer but worse. So depends if it's in the UFH circuit only. Ideally it wills be. A low loss header just isn't needed, it adds nothing to improve things, but adds distortion (increases return temp and flow temp to decrease CoP). Assuming you are running single zone? Not lots of thermostats?