This is a spin-off thread from here in order to clarify and hopefully simplify the instructions given, particularly for @morgan.

The bit of hardware we're discussing is this one. It's an adapter that plugs into the CN105 socket on the circuit board of the Ecodan's FTC (flow temperature controller) unit.

You should be able to see that, next to where the wire plugs into the little rectangular doohickey there's another empty socket. The idea is that, after turning off the heat pump so there's no power to the FTC, you remove the existing Mitsi wifi adapter from the CN105 socket on the circuit board and plug the free end of the long lead in the picture above into that socket in its place. You then plug the Mitsi wifi adapter back into that free socket I've just mentioned, effectively ending up with a really long lead between the FTC and the Mitsi wifi adapter, but with the new doohickey in the middle of the chain.

Once you're done with that, you can put the cover back on the FTC box and turn the heat pump on again. At this point, your Mitsi wifi adapter will connect again to Melcloud and you're in exactly the same situation you were before you started. In addition, once the power is on again, you'll see the little doohickey showing a blue LED. That means it's in its default config and ready to be set up.

Recapping for a moment (as outlined in the previous thread), a prerequisite for using this little box of tricks is that you've set up something for it to talk to - technically known as an MQTT broker (or server). @morgan, you've already done this by setting up the Mosquitto addon in Home Assistant, and creating a new Home Assistant user that'll be dedicated to just this conversation. The bits of information you'll need access to now are:

• the name of our home wifi network and the password to connect to it
• the name of your Home Assistant server (almost certainly homeassistant.local)
• the name and password for your new Home Assistant user you've set up for this job

Moving back to the doohickey again, whilst it's glowing blue it's acting like another wifi hotspot. Using your phone, you can go to the wifi settings and, instead of connecting to your home wifi network, you should be able to see and select a new wifi network called "Ecodan Bridge AP". As soon as you connect to that wifi network, you will be able to fire up your phone's browser and put in an address of http://192.168.4.1

Once you've done that, you'll see the WiFiManager screen the documentation tells you about. It looks like this (except for being entitled "WiFiManager").

You need to click the Configure button and you'll see a new screen looking like this.

The bits you need to fill in are the ones I've marked with red arrows.

• The SSID and password are the name of your home wifi network and the password to connect to it.
• The primary MQTT server is the name of the Home Assistant box. Most likely you'll fill it in with exactly what I've got in my screenshot.
• The primary MQTT username and password are the username and password of the Home Assistant user you created.

If it's easy enough to fill all those bits in on your phone, do so, but the key is the wifi network/password combination so the little doohickey can be visible on your home network.

Once you've filled in the necessary fields, use the blue button at the bottom to save the config and then you can disconnect your phone and reconnect it to your home wifi again.

At this point, your new little doohickey should be glowing green which signifies it's connected to the wifi network successfully. If you should need to get back to that config page for any tweaking of MQTT settings, you can now do so much more easily by simply going to one of your home PCs, opening up a browser and going to https://heatpump.local.

Now we move our attention to Home Assistant. If you go to your Home Assistant page and then, on the left-hand bar, click on the Settings cog you can navigate to your Devices and Services page. Assuming everything's been set up OK a few weeks ago you should now see a new device in the top left corner marked "MQTT". That'll be because Home Assistant has autodiscovered this new device talking MQTT to the broker. You can now click on that MQTT icon and it'll take you to a page that looks like this

Given you've used Home Assistant before, I'm guessing this won't look too unfamiliar for you, but at the bottom of each of the boxes in the middle column you'll have a link to "add to dashboard". This will add all the stuff in that box to a dashboard of your choosing so you can find it easily.

From that point, you've got your Ecodan added to your Home Assistant so it can do some local control, but you've also got the heat pump still talking with Melcloud so you can still do what you always did before and Havenwise can still do its stuff exactly as it was doing before. Nothing lost and much gained.

The only thing remaining now is, as @sheriff-fatman said, to tidy up your dashboard(s) so you can see key information easily rather than just be presented with a sea of good but potentially irrelevant bits of data.

Does that help?