Heat Pump Sizing?

michaels

matelodave said:

For those who wish to get into the weeds, this bloke has been writing some interesting stuff some of which is relevant to the discussions above. Check the articles in the menu on the right hand side

 https://protonsforbreakfast.wordpress.com/

He is Michael de Podesta, who worked for the National Physical Laboratory for 20 odd years and so has a pretty good grounding in data collection and analysis, He has been measuring and monitoring of his heatpump, solar and battery systems and trying to make sense of some of the data.

There goes several hours of my life - thanks for the link.

michaels

QrizB said:

michaels said:

I'm wondering if the rate of cooling with the heating off might be used as a proxy for the loss of stored heat. Obviously a bit simplistic as potentially the air (measured temp) probably cools quicker than the fabric.

Unless you're living in a refrigerator, or have left a door open, or if it's summer and you're trying to keep cool, the air won't be any colder than the inner surface of your house. If it was cooler, the house would be trying to warm it up and heat would be flowing in the wrong direction.

michaels said:

However to what extent is it fair to say that if the heating is off for an hour that would have needed 6kwh to maintain inside temp then you would need an extra 6kwh on top of the normal maintain temp input to return to the original temp?

For a short outage (an hour or two) that's probably a reasonable approximation.

For a longer one, as the building cools down the delta-T gets smaller and the rate of heat loss will decrease (like R_R described, and the same phenomenon you see with your radiators). So the energy needed to warm back up will be less than simply multiplying 6kWh by the time it was off.

Spies said:

Very informative post QrizB
Should I in that case have my heatpump offset to say +4c whilst the IOG hours are in play? 

Maybe? There's probably a discussion to be had about using the building structure as a storage heater, but this might not be the right thread for it

My thinking was that the air is probably cooled more by air changes (draughts) than it is by the fabric of the house cooling and that temperature of the air with the heating off would fall quicker than the fabric and the recovery energy would be more about regaining the air temp than regaining the fabric temp?

Our heat pump is much happier today when it has been slightly warmer - we don't have the in-unit axillary immersion enabled and I am wondering if this impacts on the defrost cycle efficacy - in theory we have a fair bit of water in the pipes and rads so should have enough energy stored that circulating this would provide a full defrost. Earlier today when the unit looked extremely white I ran 20 mins of 'cooling' at 10C which seemed to clear it.  When it is iced up to the extent the airflow through the fins is blocked the efficiency seems to fall off a cliff.

nxdmsandkaskdjaqd

I have the need to check the sizing of my ASHP.  Could you recommend some on-line software that I could use?

Spies

nxdmsandkaskdjaqd said:

I have the need to check the sizing of my ASHP.  Could you recommend some on-line software that I could use?

Heatpunk is an amazing resource, it allowed me to double check Octopus' figures (and they were pretty accurate).

matelodave

Heating Degree Days is worth exploring = https://protonsforbreakfast.wordpress.com/2022/03/15/heating-degree-days1-a-brilliant-idea/

michaels

nxdmsandkaskdjaqd said:

I have the need to check the sizing of my ASHP.  Could you recommend some on-line software that I could use?

Can you accees your half hourly smart meter gas usage data (assuming you currently have mains gas) as this will give you a good idea of what you actually used and you can compare that to historic temp data (the link above to degree days or find a local weather underground site) - find a particularly cold day and see your typical hourly gas usage.

NedS

michaels said:

nxdmsandkaskdjaqd said:

I have the need to check the sizing of my ASHP.  Could you recommend some on-line software that I could use?

Can you accees your half hourly smart meter gas usage data (assuming you currently have mains gas) as this will give you a good idea of what you actually used and you can compare that to historic temp data (the link above to degree days or find a local weather underground site) - find a particularly cold day and see your typical hourly gas usage.

And don't forget to adjust any gas usage figures to allow for the efficiency of your boiler (typically 85-90%) when determining the actual heat output delivered to the property.

nxdmsandkaskdjaqd

Spies said:

nxdmsandkaskdjaqd said:

I have the need to check the sizing of my ASHP.  Could you recommend some on-line software that I could use?

Heatpunk is an amazing resource, it allowed me to double check Octopus' figures (and they were pretty accurate).

Tried Heatpunk, worked well.

michaels

So I mentioned above that if we had a power interruption then my heat pump was losing its settings and returning to standby rather than going back to whatever mode it was in before.  I tried to find a bios style battery on the controller board but to no avail.

So instead I purchased a 'new to me' controller from eBay.  I now seem to be one step further forward as this controller at least remembers the on or off status of the heat pump but it also has the same problem as the old one, it loses the time setting and defaults to 'holiday' programme which basically means defrost only.

I would love to talk to an LG tech about this but can not find any contact details for LG heat pump support - has anyone had any luck with this?  I am wondering if I could use a controller from a more recent model of the heat pump series as these controllers, where available, are pretty old.  I think the heat pump is about 10+ years old.

matelodave

My fourteen year old Daikin does summat similar.

It restarts after a power cut ( "auto restart" has to be enabled or disabled in the engineering menu) and all the timing and configuration settings are retained, however, the day and clock always resets to Monday 00:00 and the clock restarts from there.

Probably not as bad as yours if all the settings are lost but a bit irritating as we get quite a few power drop-outs, so the clock day and time has to be reset every time it happens.

It wouldn't be quite so bad if the clock held up for half an hour or so (or even a couple of minutes)