LG therma v ASHP with solar PV and batteries

[Steve5260]

Hi,

 

im new here and it’s very possible this has been asked previously 

 

I have a new self build and my heating is with ASHP, a LG therma v

 

i have recently completed my solar PV I have 7kw with a 12kw battery. It’s all works perfect, apart from one slight issue.

 

at time my AHSP will call for power and the max my batteries can discharge is 4.5kw (I think), because the ASHP is calling for more even though my battery has plenty of power the system will have to take from the grid as well as batteries. 
 

ling story short is there any way of adjusting the ASHP to limit the power it pulls??

 

thanks in advance 

 

Stephen 

[DanDee]

15 minutes ago, Steve5260 said:

Hi,

 

im new here and it’s very possible this has been asked previously 

 

I have a new self build and my heating is with ASHP, a LG therma v

 

i have recently completed my solar PV I have 7kw with a 12kw battery. It’s all works perfect, apart from one slight issue.

 

at time my AHSP will call for power and the max my batteries can discharge is 4.5kw (I think), because the ASHP is calling for more even though my battery has plenty of power the system will have to take from the grid as well as batteries. 
 

ling story short is there any way of adjusting the ASHP to limit the power it pulls??

 

thanks in advance 

 

Stephen 

I general the only way to control the output is to limit/reduce the dt and flow rate, the minimum flow rate and the minimum dt in the technical book.

 

By limiting the output it inherently limits the input. Apart from the start-up when whatever the software of the HP will decide that it needs to run at higher frequency after certain period of low frequency runs in order to bring the oil back to the compressor.

Edited May 14, 2023 by DanDee

[Steve5260]

Thanks for the reply. 
do you mean reduce the set temp

on the DHW?

[ReedRichards]

If you have enough solar power to charge your battery it's probably not the middle of winter.  Most of the rest of the time, my LG Therma V uses most power when heating the hot water.  So when I have spare solar power I heat my hot water using the immersion heater (3kW).  That's wasteful of energy but means that the electricity is all free, rather than topped-up from the mains.

[sharpener]

Many HPs have a programmable night mode setting that reduces the max allowable compressor speed to make it quieter, that ought to do it. And if actually at night then you benefit from cheap rate as well (assuming you have got E7 or one of the many Octopus tariffs). It will take longer to heat to a given set temp but you have 7 (or 4 or whatever) hours which should be more than enough.

 

Reducing the set temp will always be helpful as it will improve the CoP in DHW mode.

 

But I am surprised if in winter at least your 12kWh battery is going to make much of a dent in the HP's overall energy demand.

Edited May 14, 2023 by sharpener

[eniacs]

Struggling to see how your heat pump is drawing more than 4.5kw? Is it massive?

 

I've got a 12kw heat pump, this draws 2.5kw when running. I time it for the afternoons 1pm to 3pm, the battery is fully charged from solar and there is usually spare solar to run the HP. In times of no sun, i can run it in the octopus night time rate which runs from the grid anyway, or run it on battery in the day then charge the battery at night.

[PhilT]

1 hour ago, eniacs said:

this draws 2.5kw when running.

Varies enormously - time of year, time of day, peak startup or continuous, heating or hot water. My 11.2 draws anything from 1 to 7kW. More to the point, why the concern about the relatively small amount of draw from the grid in excess of battery power during the short start up times?

[sharpener]

10 hours ago, eniacs said:

I time it for the afternoons 1pm to 3pm, the battery is fully charged from solar and there is usually spare solar to run the HP. In times of no sun, i can run it in the octopus night time rate which runs from the grid anyway, or run it on battery in the day then charge the battery at night.

 

I plan to do this too. Have you got a thermal store so you don't need to run it much outside these (cheap) times, or a very big battery to supply 2.5kW for hours on end. How big is that?

[eniacs]

I am on the site to help me install my house heat pump, so it isnt up and running yet. The 12kw heat pump i already have is the pool heat pump, it is in itself a large buffer tank!

 

We have a 28kwh battery and 9kw of solar so power during the 3 warmer seasons is no problem. In the heating season, the house can stay quite warm all day having been heated in the 4 hour octopus period. We also hope to be able to run the house heat pump for a few extra hours on cold days to top up the house temps. This last winter, we had no heat pump, all heating was via oil filled direct resistance radiators powered by the battery and the night time octopus go rates.

 

[sharpener]

On 18/05/2023 at 15:58, eniacs said:

We have a 28kwh battery

 

Nearly 3x the size of mine then, no wonder it is sufficient. Am contemplating a thermal store as cheaper/kWh. Had two HP installers visit in the last two days, neither v impressive so didn't discuss fitting a TS as didn't want to confuse the base quote.