ReedRichards

The person who did it was a qualified electrician but did not appear to understand the terms "series" and "parallel" in the contest of electrical circuits so you must judge for yourself if they knew what they were doing. However it is beyond a shadow of a doubt the same circuit. The wiring via the control box is the same as it was at the first attempt but connected to the fuse box side of the switch. This places the switch in parallel with the immersion control box rather than in series as it was first time around. I thought about this before asking for it to be done but could not think of any adverse consequences. And nothing has gone fut so far. Whereas if the contactor is manually energised then the controller might be able to detect this and so get confused.

On the outside of my hot water cylinder is a large box (see picture). I don't know if everybody gets one of these but it's function is to allow the LG controller to turn on the immersion heater (that is just below it) which heats (or can heat) the DHW. AFAIK this is used solely to raise the temperature of the water to 60 C for the legionella cycle. To use the Willis heater as well would be belt and braces, surely? And if you could use just the Willis heater then that big box would be redundant. What you can't quite see in the picture is that I have two wires going to my immersion heater. They are both on the same circuit but one goes via the box and one goes via a switch that I can operate independently. I just wondered if that was the norm. I had to do a bit of persuasion to get it done that way and I was chatting to someone who "lost" their immersion heater switch when their new cylinder was installed.

@ProDaveSurely the heater you refer to is part of a closed loop and does not need to legionella cycle?

Yes, I did mean the immersion heater for the hot water. My buffer tank also has an immersion heater but it's not wired in, so it's there but not used.

Question: Can you operate your immersion heater independently of the heat pump? I had some teething troubles with my heat pump when it was first installed and the error code on the controller meant that I lost all control. I wanted hot water but found that the switch for my immersion heater had been wired in series with the internal switch so I had to do some emergency rewiring (then get the electrician back to fix this). Now I am reading of another instance of someone in the same situation. Surely it should be standard practice to ensure that the immersion heater can be used independently?

Just FYI, this is my entire house electricity consumption for 7th March. The highest peaks are mostly heating the hot water but could be cooking.

@Chris Bottomley, yes my Drayton Wiser programmer will tell me the minimum and maximum temperatures for each day without the benefit of a temperature sensor. Possibly it uses this information for its "Comfort Mode" which tries to reach the desired temperature (increase) at the time set for that increase to occur. Do you feel you are benefiting from the RHI Monitoring? I just opted for the minimum requirement, which is metering.

@ProDave, May I ask what relay you actually used (make and model)? I seem to remember seeing something inside the big box on the side to which the thermostat is wired that looked a bit like a relay (a large component inside a transparent box). At the time I was looking to see how I could correct an error by the installing electrician who had wired the immersion heater in series with my own time switch instead of in parallel. This was when I had the CH14 error and found I could not even use the immersion heater when the heat pump was not wanting to play ball. That is corrected now.

@ProDave, that's an ingenious solution but also emphasises how easy it would have been for LG to have done something themselves. How did you mount the relay? When I read your initial posts I was focusing on the CH14 error as I had experience that very briefly until a filter was changed.

@Chris Bottomley I'm glad you came back; I think we users all need to work together to find out how to get the best performance out of our heat pumps. My system is set up the same way as yours but this means that I cannot turn on the hot water remotely after I have been away, although my central heating programmer has the capability to do this. As with you, I drop the demanded temperature overnight. At the moment my hot water is on all the time except overnight. I will try to use the immersion heater on sunny days as that heater has a power requirement (3 kW) that is better matched to my solar panel output. The water setting is the target temperature for the inlet water. My system was set-up for this to be 50 C but I have been running at 40 C since the weather turned warmer. I suspect that I have dome manually what the AI mode tries to do automatically. The heat pump has an outdoor temperature sensor but does not report what it reads. Perhaps a software/firmware update could fix that? My software version is 3.05.6a .

When I tried to use the AI mode it failed to reach the room temperature I had set. But then the system had been in operation less than two months so perhaps it had not had enough learning time? How long do you think it needs to build up decent historical records? Also you can set AI with numbers (-5 through 0 to +5, I think). What do the numbers mean? And a general query: do you have your own programmer? If so: can you use it to time the hot water? Is the "Select temperature sensor" set to Water or Air + Water. In my case my programmer cannot time the hot water because it was set up that way but I don't see why it should be a problem. And Select temperature sensor is set to Water. I can see this will avoid conflicts with my programmer but it must limit the scope for intelligent control.

@SteamyTea seems to have gone off the boil, or off to boil a kettle, but I have some thoughts for @Chris Bottomley During the recent cold spell my Therma V was using up to 48 kWh per day running at a 50 C flow temperature. But it managed to keep the house at the desired temperatures and took two to three hours to raise the temperature by 1 degree C. Now that the weather has turned mild I have been experimenting with the flow temperature and 40 C seems fine and will raise the temperature after the nighttime setback at a similar rate. I am now using about 25 kWh per day. In the installer settings you have the choice of 3 settings for the temperature sensor, Air/Water/Air+Water. My guess is that you need to set Air + Water if you want the AI mode to pay attention to the room air temperature. My installer set this setting to Water to avoid unwanted interaction between the LG room thermostat and my own (Drayton Wiser) programmer.

You're going to have to explain "historical usage patterns" in some detail if you want me to understand what you mean. There is a buffer tank built in to the base of the hot water cylinder.

Hello all, I have had a 12 kW LG Therma V for a little over 2 months now It ran for less than 24 hours and then stopped with a CH14 error. The installer came back, concluded that a filter inside the unit was blocked and fixed it. It has not misbehaved since. Hogboon, I think the raised finger to the lips symbol probably indicates "Quiet Mode" - because the symbol is saying "Shhh". I have experimented with the (undocumented) AI mode but it just resulted in a failure to reach the set temperature. This does not happen if I control the outlet water temperature. I have my own room thermostat and I find it hard to believe that the AI mode can work with anything other than the LG-supplied room thermostat because I don't believe you can control intelligently without knowing the difference between the actual room temperature and the desired room temperature. When the heat pump gets a call for heat, it waits about two minutes then turns on its pump. It then runs for about 4 to 5 minutes before it turns on the 'Outdoor Unit' to supply heat. If the room temperature is near the desired temperature the thermostat might decide momentarily that the room was hot enough and then the cycle would have to start all over again. I ended up telling my thermostat that it was controlling an oil boiler which then limits the number cycles per hour to 3. Even so, most of the time the heat pump cycles; I have not yet worked-out how to get it to supply a lower level of heat more continuously.