Ecodan, which controller

[Tim S]

Hi everyone.

Background : plumber installing self specced ashp / UVC next week. No grant available so no MCS install as they are a rip off.

 

Hi everyone, I’ve got myself confused over what Mitsubishi controller does what. I’m aware the two options for controlling an Ecodan are the FTC6 and the FTC2BR, I’ve read the Mitsubishi info on both, but it’s clear as mud to me which one I need.

 

system is 5kw Ecodan on S plan architecture for UFH and DHW, no rads. Non Mitsubishi UVC due space restrictions and budget constraints. I got a package from Wunda including room thermostats (4 zones) and their H box wiring centre. Wunda designed the pipe installation and I’ve analysed the heating demand on one of the spreadsheets used by forum members on here. It’s a part self build, so the thermostats are already in. However, it seems that since i bought the kit from Wunda about 3 years ago, the philosophy of how to manage the heat pump has changed, and I would like to embrace weather compensation/ setback etc, and am also wondering if the H box wiring centre is needed….

 

Can anyone advise me which controller would be best, which will work with the third party thermostats, cylinder, Wunda H box wiring centre (do I even need this)but allow me in due course to use weather compensation etc. Thanks in advance, and apologies for asking a numpty question!

 

 

[JohnMo]

31 minutes ago, Tim S said:

5kw Ecodan on S plan architectur

I assume you don't really mean S plan, but 2 x 2 port valves one normally, the other normally closed, so you don't feed the cylinder as well as the UFH, at the same time. I would keep it simple with a 3 port diverter - normally closed side to cylinder.

 

4 zones is likely to require a buffer also. Have you considered that? If you are doing a buffer 2 port is best.

 

You would connect something like this (below image) the room thermostat would control the heating pump only - top right of cylinder, the buffer cylinder would control the heat pump on off.

 

 

If you are well insulated and airtight WC is an unnecessary complication. Tried every conceived option and a set flow temp is easier.

 

To be quite frank, if you have anything remotely thick in way of screed the Wunda thermostats are too big a hysterisis, to give very good control.

[ReedRichards]

18 hours ago, JohnMo said:

If you are well insulated and airtight WC is an unnecessary complication.

 

Weather Compensation is never necessary but it ought to save you money, surely?  And it's certainly a complication because you need to work out how to set your water temperature based on what the outside temperature is.  Bit just because @JohnMo didn't manage to do that doesn't mean that you won't.  Weather Compensation works fine for me.

Edited April 8 by ReedRichards

[JohnMo]

16 minutes ago, ReedRichards said:

Bit just because @JohnMo didn't manage to do that doesn't mean that you won't.  Weather Compensation works fine for me.

I certainly managed, but running a target fixed temp mostly in the E7 period is just cheaper.

 

Also if doing WC why do zones?

[ReedRichards]

On 08/04/2024 at 08:19, JohnMo said:

I certainly managed, but running a target fixed temp mostly in the E7 period is just cheaper.

 

Also if doing WC why do zones?

 

You didn't mention the E7 part first timer around.  Having Economy 7, or a similar Electric Vehicle charging tariff, can really skew the normal economics of operating a heat pump.

 

You can have a gas boiler that does WC and nobody objects if your heating system also has zones.  Weather Compensation doesn't have to be as "hard core" as the Heat Geeks and their ilk would like it to be.  When you start to sacrifice comfort for the sake of a bit more cost saving, where do you draw the line?  Why not go the whole hog, put on your outdoor clothes and turn off the heating?  

[JohnMo]

17 minutes ago, ReedRichards said:

When you start to sacrifice comfort for the sake of a bit more cost saving

Why would that happen with a well set up system. He has UFH not radiators. My gas system started with lots of zones, consumption of gas was through roof. Did various forms of WC (with a d without zones), fixed temp for long periods works really well.  I did lots of experimenting with the gas boiler and batch charge worked out cheaper with that also.

[sharpener]

On 07/04/2024 at 12:38, Tim S said:

the two options for controlling an Ecodan are the FTC6 and the FTC2BR

 

Am no Mitsi expert but having read the FTC6 instructions in connection with this thread I had a quick look at the FTC2BR, it is what is packaged with the smaller Ecodans and I think should be sufficient for your purposes as you do not want to control multiple circuits or mixing valves for which the FTC6 is required. AFAICS it will do WC and accept a voltage-free input assuming that is what the Wunda Hbox setup provides.

 

As many have said in the past the best approach is often to utilise the individual zone stats more as a high limit set to 22C or so and drive the whole house as a big open circuit (whether using WC or fixed temps). That way you can avoid using a buffer - subject to the total volume being sufficient for defrosting. The room stats can be trimmed down as a later adjustment to allow for solar gain or lower temps in bedrooms.

 

 

Edited April 15 by sharpener

[Tim S]

51 minutes ago, sharpener said:

 

Am no Mitsi expert but having read the FTC6 instructions in connection with this thread I had a quick look at the FTC2BR, it is what is packaged with the smaller Ecodans and I think should be sufficient for your purposes as you do not want to control multiple circuits or mixing valves for which the FTC6 is required. AFAICS it will do WC and accept a voltage-free input assuming that is what the Wunda Hbox setup provides.

 

As many have said in the past the best approach is often to utilise the individual zone stats more as a high limit set to 22C or so and drive the whole house as a big open circuit (whether using WC or fixed temps). That way you can avoid using a buffer - subject to the total volume being sufficient for defrosting. The room stats can be trimmed down as a later adjustment to allow for solar gain or lower temps in bedrooms.

 

 

Ok, now I am really confused, as I phoned Mitsubishi UK pre sales to find out the difference between the two and the man said that if I went for the FTC2BR I would have to buy a BEMS system and that that was way more complicated and expensive, and to go for the FTC6. I was wondering why the FTC2BR was available as a package if it was so specialised…!

 

I ideally want to do what you suggest - use a fairly simple controller, zone stats as coarse control, mixing valve as a safety in case of over temp and use the slab as the buffer (not sure if you twigged the other thread about having problems getting in the trades to fit it all was mine btw).

 

I’ll get back in to the manuals tonight and see if I can make some sense of it all…

[sharpener]

1 hour ago, Tim S said:

if I went for the FTC2BR I would have to buy a BEMS system

 

That's what might be inferred from this incredibly unhelpful piece of publicity material but AFAICS it will be entirely adequate when fitted with this H-box 12 or similar, this is the "third party control" referred to.

 

The H-box does indeed have the voltage-free relay output you need, which is an OR-function of the individual room stat demands. As it says on that spec sheet, any one room stat will then be sufficient to call for the HP to run. So you just need to wire those two terminals to the FTC2BR, job done. The Mitsi instructions are very easy to follow and personally I would have no hesitation in tackling the wiring as a DIY.

 

BTW I take it you mean a mechanical tempering valve on the manifold, not an electronic one which is unnecessary given you do not have any rads.

 

Yes although @mk1_man is in some ways in a similar position I had worked out it was yr own thread.

 

 

 

Edited April 15 by sharpener

[Tim S]

9 minutes ago, sharpener said:

 

That's what might be inferred from this incredibly unhelpful piece of publicity material but AFAICS it will be entirely adequate when fitted with this H-box 12 or similar, this is the "third party control" referred to.

Yes I have the H box.

 

The H-box does indeed have the voltage-free relay output you need, which is an OR-function of the individual room stat demands. As it says on that spec sheet, any one room stat will then be sufficient to call for the HP to run. So you just need to wire those two terminals to the FTC2BR, job done.

Great.

 

9 minutes ago, sharpener said:

 

BTW I take it you mean a mechanical tempering valve on the manifold, not an electronic one which is unnecessary given you do not have any rads.

Correct, basic mechanical. I was wondering about the usefulness of this, but it makes sense to use it as overheat protection. Again correct, no rads, just UFH.

9 minutes ago, sharpener said:

 

Yes although @mk1_man is in some ways in a similar position I eventually realised it was yr own thread.

 

 

 

Big thanks for your input, very helpful.