@sand

The photo of the radiator looks like a standard steel type 22 (k2), two panels and two fins. The k3 will have three panels and three fins (as @derek-m also points out above).

Thanks Rusty, great info, learning loads.

Hi @sand

Your pipework and setup seem very similar to mine.

Red pump in 4th pic is the pump that pushes hot water around all your heating system.

Red balloon like expansion tank is to handle excess pressure for the heating system.

White expansion tank is to handle excess pressure for DHW.

The flow to heating/DHW is controlled using Synchron valves, not a 3 way diverter valve as Derek said might be the case.

The DHW tank is self insulated so no, you don't need to add extra insulation.

Your FTC controller (what you use to change the ASHP settings) is located in the garage. With it located there you can use weather compensation but cannot use auto adaptation.

Hope that helps.

Thanks so much MarkC brilliant information. Good to know that tank does not need to be insulated.

@sand 

You’re welcome, I never know whether to reply on things like this, as it’s not easy to know how much people already know, don’t want to “teach grandma to suck eggs”.

If you are contemplating swapping out the rads, just be aware that, assuming Stelrad, the K3 will be around 50% deeper than the K2, but with around 40% more heat output for the same size panel. You can estimate the output power of the existing panels by simply measuring them and looking up the K2 range data on the web (sorry, that may be obvious), though beware that this may be at a delta-t of 50C (i.e. traditional 70C flow temp for a 20C room temp), at 45C flow temp the power output will obviously be lower and would need estimating. You can then see if the rad size is adequate for the room if you know the room heat loss estimate. On the Stelrad website there is a useful heat loss calculator that can be used to estimate this, based on flow temp, room size, desired temp, etc. Not promoting Stelrad, it’s just a useful example, there are others!

@markc 

Can you expand on why auto adaptation cannot be used, but weather compensation can? Is it simply that the location means that the room temperatures aren’t available while the external temperature is available. That seems odd, as from the brief description that I found, auto adaptation seems ideal and it’s just a communications issue with the room thermostats.

Thanks Rusty I know absolutely nothing about heating and never thought  I would need to ! Then bought this house (with a ashp so had to quickly learn. Info re rads is great.

Sorrry forgot to ask re rads would aluminium or cast iron rads work with ashp low flow as long as they were K3. Do they even do K3 cast iron. 

Posted by: @rusty

@markc 

Can you expand on why auto adaptation cannot be used, but weather compensation can? Is it simply that the location means that the room temperatures aren’t available while the external temperature is available. That seems odd, as from the brief description that I found, auto adaptation seems ideal and it’s just a communications issue with the room thermostats.

That's exactly it. Weather compensation uses the external thermistor whereas auto adaptation uses both the external thermistor and the internal thermistor located in the FTC control panel to read internal room temp and adjust the flow temp as required.

For auto adaptation to work the FTC needs to be located in a room/hallway. A location where a typical central heating system would have its single thermostat.

So for example imagine outside temp is 5ºC on a cloudy day, so the compensation curve sets the flow temp to 30ºC. This generates an internal temp of 22ºC.

The next day is also 5ºC outside but is a sunny day. The curve would also set the flow temp to 30ºC, but the solar gain on the windows and building fabric make the internal room temp 25ºC.
The FTC located the room knows it's 25ºC inside, so reduces the flow temp accordingly.

If on the other hand the FTC is located in the garage, this feels no solar gains doesn't adjust the flow temp.

@markc 

Is it safe to assume that if the FTC is in the same cupboard as the cylinder etc (common instal procedure) that, like the garage scenario, auto adaptation is not an option?

Posted by: @morgan

@markc 

Is it safe to assume that if the FTC is in the same cupboard as the cylinder etc (common instal procedure) that, like the garage scenario, auto adaptation is not an option?

It appears to be the common practice yes.

For Mitsubishi ASHPs, if you want to use auto adaptation the options are:
1. Move the FTC controller 
2. Wire in an additional thermistor and locate that in the room/hallway.
3. Add an additional, wireless FTC controller and local that in the room/hallway.

I think the current opinion is that using auto adaptation instead of weather compensation only won't give massive economic savings, but it will help to maintain a more comfortable internal temperature.

At the moment my FTC6 is in the airing cupboard with the cylinder etc and it will remain there.

The thermostat at present is a Heatmiser Neo which I didn’t want and don’t like but my installer is unable to get stock from Mitsubishi so had to go this route to complete the instal prior to winter.

I’m now in possession of a Mitsubishi remote controller ( https://les.mitsubishielectric.co.uk/products/controls/remote-controllers/par-wt50r-e-remote-controller ) and await the delivery toward the end of January!  of the wifi receiver ( https://les.mitsubishielectric.co.uk/products/controls/remote-controllers/par-wr51r-e-remote-controller-receiver )

When I have possession of both the installer will return and swap out the Neostat.  I should then be able to run a ‘proper’ weather compensation set up and access Melcloud applications.  Not too bothered with auto adaptation.