Posted by: @trbob

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Just checked my settings on the controller and the target temperature is 61°C for 5 minutes.

How does the Ecodan unit know that the DHW tank has reached the target temp?

Is it possible that your immersion heater has been set internally to 59°C ?
It's a tiny adjuster screw. Anywhere in the vicinity of 60°C would probably look satisfactory to an installer.

I didn't know that this is the way that it would work, I assumed that the Ecodan would be reading the temperature of the DHW tank and adjust accordingly.

I'll have a look to see whether I can adjust it easily.

Well, the Ecodan might have its own temperature sensor on/in the DHW tank.

But an ordinary immersion heater only has internal thermostats.
One is adjustable, and the other acts as a fail-safe unit.
It doesn't send information down a wire to another device.

If you spot any wires connected to stuff on the sides of your cylinder, post a photo here and we'll see if it might be sensing water t3emperature.

@transparent I can see my DHW tank temperature in the MELCloud app, hence why I thought that it would 'know'.

Posted by: @trbob

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@transparent I can see my DHW tank temperature in the MELCloud app, hence why I thought that it would 'know'.

Many, if not most/all, ASHPs have their own tank sensor.  Unlike the immersion thermostat it is analog not on/off so that the ASHP knows the actual temperature not just whether it is above or below a setpoint.  I would be very surprised indeed if yours doesn't have such a sensor, usually in a pocket perhaps half way down the tank.

Perhaps it works out the DHW temperature by using a thermostat on the return flow back to the heat-exchanger.

But, if so, then that would suggest the heat-pump keeps the circulation water flowing whilst the immersion heater is taking the cylinder up the last stage from 50°C to 60°C.
I rather doubt that.

Just because an App reports information to me doesn't mean I believe it.
I'd want to check where it gets that data from.

After all, you probably also have a piece of paper telling you that the ASHP installation complies with Building Regulations...
... but that too could be a work of fiction! 😉 

Here's a temperature probe in a 'pocket' on the side of my tank.
So this is the sort of thing you're looking for @trbob

You'll see I've also stuffed another couple of temperature sensors alongside that pocket.

@transparent

 It looks like the element is set to it’s maximum. Pretty sure that the grey wire halfway up the tank is a temp sensor right?

Posted by: @trbob

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@transparent

. Pretty sure that the grey wire halfway up the tank is a temp sensor right?

I would say for sure assuming it connects to the heat pump controller.

Yes I agree with @jamespa - that's the temperature sensor, stuffed into an open-ended copper tube.

If you closed off the end with a piece of foam, it might even be able to record the right temperature!

I've also highlighted the Tundish on the right.

The pipe entering at the top should come from a pressure/temperature release valve.

It 'explodes' into the Tundish, which is open to the air on its upper regions.
The exit pipe should be larger diameter, and take the scalding water away outside somewhere.

The idea is to have the hot fluid taken to the exterior of the house via the larger pipe with as few bends/restrictions as possible.

Just have a look and check you're happy with that arrangement.
I have occasionally seen Tundish units installed upside down, for example! 😲 

May I point out that many heating installers don't understand the role of a Release Valve and Tundish, and may not have seen them operating.

The best moment to check that it's functional is when the DHW tank is at full pressure and temperature, and whilst the installer is still on site, but looking the other way.

Grasp the knob on the release valve and turn it sharply 90° anti-clockwise.
There should be a sudden rush of water and a loud noise as it expands into the tundish.

The effectiveness of the safety mechanism is directly proportional to the height attained by the installer above Floor Level (FL) in response to the sound of fast-moving water behind him.

The trajectory isn't relevant.
We're not particularly interested in the horizontal component of the moving body...
... unless that has taken him through an open window.

@transparent But it may be necessary to ‘clear up’ behind the installer! Toodles.