Posted by: @ak2024

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Posted by: @ak2024

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When I increase the temperature, only after 5-10 mins it show the play button on the screen, and then you can hear the system starting up.

 

My Ecodan can take 5 minutes but not as long as 10.

For me too.

I suspect in our case that it may be some kind of soft start to both keep the noise down and to avoid hitting the circuit board with the load suddenly. Alternatively I could be talking small spherical objects. Either way, it certainly isn't the instant reaction you'd see with a boiler.

So I had a bit of unofficial assistance on this one.

Typically, if the lightning bolt symbol appears, it indicates the immersion heater has been activated. However, the system can only send the signal to activate the immersion; it has no way of confirming whether it’s functioning properly.

If the immersion heater is faulty, the system won’t detect this.

Besides the legionella cycle, there are three fault conditions that could cause the immersion to activate:

1. Poor flow rate
2. Narrow delta T
3. No temperature rise of 1°C within 10 minutes (in hot water mode only)

If the issue were a low flow rate, you’d likely see an error code. So, it’s more likely to be either issue 2 or 3.

DIP switch SW1-4 enables the system to control the immersion heater, so it’s worth confirming that this is switched on.

To test the immersion heater, go to the service menu, select heat source, and change the setting to heater only, which will instruct the system to use just the immersion heater. The lightning bolt symbol should appear. Monitor the hot water temperature displayed on the home screen. If there’s no increase after 10–20 minutes, it’s a strong indication the immersion heater is faulty.

I just timed mine, adjusted the underfloor hardwire controller, and it took 15 minutes.

Posted by: @editor

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To test the immersion heater, go to the service menu, select heat source, and change the setting to heater only, which will instruct the system to use just the immersion heater. The lightning bolt symbol should appear. Monitor the hot water temperature displayed on the home screen. If there’s no increase after 10–20 minutes, it’s a strong indication the immersion heater is faulty.

I'm afraid that if I change anything on the service menu, the installer might say that I've altered the settings. However, I did suggest to the installer on numerous occasion for them to manually enable the immersion heating and see for themselves, but they just ignored me, maybe because they don't know how to do it? Nevertheless, I dug up this YouTube video to show to them next time they come, https://www.youtube.com/shorts/SC0O_7_WE3I which I believe it's the same advice you've just given.

Mitsubishi is coming out to replace the thermocouple for the immersion heating, and some other part outside because the system goes off with the error UL on the screen every couple of days. Also, they're changing the pump configuration because some of the radiators heating up when only the underfloor heating is on.

I'm not too sure if this is a problem or the way the system is designed, but I noticed today, it shows on the main display the tank temperature as 17°C, but the water temperature is actually 40°C, measured with the thermocouple on my multimeter.

I forgot to mention to the Mitsubishi engineer that the system was taking exactly 15 minutes for it to come on.

@ak2024 the thermistor for the tank temp is low down in the cylinder so as soon as you draw hot water the temp drops rapidly but in reality you have plenty of hot water at the top of the cylinder.  After 2 morning showers ours reads around 17C as well but there is plenty of hot water still available, so I doubt this is a problem.

I had a feeling it was the case. I guess the installers can longer say it's "User Error". They never tested the system thoroughly, also the piping and pumps were incorrectly installed, and one of the radiator was completely turned off. If they tested the system properly, they would have caught these problems.

This how my system is running :

Top graph is the amount of electricity it's consuming. The system came on about 4am, room temperature went up 1.5°C by 12pm