heat pump and pv diverter

[ewan.costar]

Hi,

I've got both a solar pv and an ashp system.

The solar system also has 2 batteries and it's configured to fill the batteries first and then export to the grid when they are full.

I don't think it matters, but the pump is an LG Therma V R32 monobloc.
From what I understand (I'm not an electrician or have any kind of technical background), the heat pump is connected to the cylinder in the attic in 2 different ways:

• it pumps hot water into the cylinder through the coil. that only takes the temperature inside the tank to between 45 and 50C.
• there's 2 wires from the pump to a box next to the cylinder (one for power and one for data). the box contains a circuit breaker and a contactor that decides whether energy is sent to the immersion heater to top up the temperature.

It's all working fine, except that I've still got an iboost+ (or similar) pending to be fitted. We've been back and forth with the installer for almost a year now.
The installers have tried the solic200 and the solar iboost+ so far without success. They designed the system with this (without specifying the model) and i didn't even know this existed before they mentioned it to me.

They've sent me a few electricians. Every new guy tells me a different thing about compatibility with the heat pump and even some times they manage to break things that were already working when trying to make it work. i've lost trust on them.
We have a bad relationship at the moment and I'd rather get this installed and working if possible rather than having to battle for a refund that may take a long long time.

the original design said that the diverter would be wired into the lg box and use energy that would go into the grid to heat the water.
however, now that i've looked into it, it doesn't make a lot of sense to me.

despite all the conversations with engineers and my own research, I'm not really an expert by any stretch of the imagination, so I would then like to ask you for your experience with similar setups. I've got 2 main questions:

• is this set up even possible? if so, do you have any details setting it up that you can share? what i understand is that when paired with the heat pump, the immersion heater would only work if lg sends the signal and there's excess energy being produced. this doesn't seem very practical to me, but maybe i'm not understanding how it really works. the electricians tell me that i can also press the boost button on the iboost, but it wouldn't really work unless lg decides it has to be on anyway. actually, the way they've tried to set it up (iboost between the contactor and the tank) means that the iboost will not even be on until lg tries to start the heater. it has not direct feed most of the time.
• if this is possible, do you reckon it's worth doing? my dhw is usually set between 48 and 50 depending on the time of the year. it's enough even when 2 people have a shower at the same time. i have a night tariff that i use to charge batteries overnight already in winter and i can schedule the pump to heat the water so that it's ready when we get up. i have no idea about the financials about both options, but again, i'm looking for a practical solution unless using iboost is much cheaper than the current set up.

I called iboost and solic manufacturers, and also LG. they all have told me that they have clients using the 2 things together, but wouldn't give me any hints/help/recommendation on how to set them up. they just don't want to offer any help with something they don't make themselves.

any help would be greatly appreciated.

thanks!

 

[ericmark]

In the main the installer does not design the system, he follows a design from the manufacturer. There is no reason why an installer can't design his own system, but most central heating it is a balance between installation cost, and running cost, so the simple way to ensure over 65°C once a week is a timer which switches on once a week so the immersion heaters thermostat allows it to heat up once a week.

To use excess power available it needs to know when there is excess power and will be excess power for say 2 hours, otherwise it is switching on/off all the time. I am sure it can be done, but the question is can it be done for a reasonable cost?

So in the main it is a case of select a day when the batteries are likely to be fully charged, and a time when there is likely to be excess power and turn on immersion heater with a simple timer at that time.

 

[ewan.costar]

yes, it doesn't seem too practical to me.
i don't really want to be keeping an eye on anything on a constant fashion. i just want to have the hot water ready whenever i need it.

having to change shower times or when i heat the water depending on the day seems too cumbersome for the average user.

 

[hllns]

There's a lot of "it depends" about various bits of this setup which is probably why it's tricky to get a definitive answer. If you've got the data it's probably worth working out how much excess power you're talking about and how well the ASHP setup is working.

 

[ewan.costar]

agreed. and when in doubt, i'd rather not do it.

without being an expert at all, i can see how you would need to do your maths for different times of the year.
in the end.... probably you are breaking even at best (pv diverters do cost a few hundred £ plus installation).

this has been my line of thought for a while but the installer keeps insisting on this. i just wanted to make sure that i wasn't dumb enough to be missing on a huge saving opportunity.

 

[hllns]

Looking at the blurb for your heatpump it seems to have a large compliment of bells and whistles and implies that you can set smart energy "states" which tell it to try and use more (or less) power, it would need some way for those states to be set when you're sending power to the grid or can buy power super-cheap but is more elegant than pressing "boost"

It sounds like you have a lot of the building blocks to do all of this, the difficulty is the controls to integrate them. The LG blurb likes to toot about needing LG solar/battery systems but this may or may not be true.