Mitsubishi Ecodan/FTC5 and Heatmiser UH8 UFH control

[cb1965]

Hi there,

 

I have just installed a Mitsubishi Ecodan ASHP and pre-plumbed cylinder with an FTC5 controller mounted to it and want it to work with a Heatmiser UH8 UFH controller. The wiring and plumbing and dip switch settings are all good and everything works with heat enable from the Heatmiser UH8 controller connected to the room thermostat 1 connection in the FTC 5.

 

My question is what do I do with the settings on the FTC 5 heating to allow the Heatmiser to control the UFH. Do I set the schedule settings or let it run 24/7? How do I tell it the 'only' thermostat connected is thermostat 1? What do I do with the max/min flow temp settings etc.?

 

First time UFH user here so all input appreciated.

Edited December 4, 2021 by cb1965

[Cedric Bainbridge]

Hi cb1965,

 

I'm guessing that as your post was nearly four years ago, you will be able to help.  I installed the same Heatmiser UH8 UFH system in my current property but used a specialist supplier to install the Mitsubishi Ecodan ASHP under the government grant scheme.  I soon started getting L9 (insufficient flow) errors on the Ecodan and on checking, the ASHP engineer had completely ignored the Heatmiser controller - nothing was connected to the heat call terminal block.  So, if one of the UFH zones called for heat, nothing would happen unless the Ecodan was also calling for heat, and if the other way around, ie. the Ecodan called for heat but no UFH zones were calling for heat, the Ecodan would shut down with an L9 error.  When questioned, the ASHP company told me that was the only way that they could install it and the Heatmiser controller was my problem! I now run the system with the Ecodan remote adjacent to the hall UFH thermostat and keep those set at the same temperature, but I also keep another UFH zone (the coldest zone in the house) permanently open (by leaving that zone's actuator off the valve).  This has been okay as a workaround.

 

Now, I am renovating a new property to move into and I have installed the same Heatmiser UFH system, and I am again using the same firm of installers for the Mitsubishi Ecodan under the government grant scheme.  However, this time, I want the Heat call from the Heatmiser to control when Ecodan calls for heat.  I am happy that they will connect the UFH pump and valves to the Ecodan FTC but I do want the Heatmiser controller to determine when heat is called for and not the thermostat that is built into the Ecodan remote.

 

I can see the terminal block TBI.1 on the Ecodan FTC on my current system which is for 'Room thermostat 1' and nothing is wired into it (nor is anything wired into TBI.2 which is for 'Room thermostat 1'.  The wiring diagram lists terminals 7 and 8 for Room stat 1.  The Heatmiser terminal block for heat enable has Ls and Lr terminals.  Do you know which connects to which? If you have any advice it would be much appreciated.

 

Many thanks.

[JohnMo]

My view is very different from some on here. Ignore if you wish.

 

Run on pure weather compensation, all zones open. Let the heat pumps native controller do the calls for heat as it sees required. Mitsubishi have a room biased temp modulation, but states this isn't to be used with UFH only suitable for radiators.

 

Your system with lots of zones needs a buffer to work correctly, otherwise you will be getting flow related issues.

[JamesPa]

Sorry I agree with @JohnMo.  Eliminate the zoning (and the heatmiser), balance the loops, let the Mitsubishi controller do what it was designed for.     Your problems will likely vanish and equally likely you can turn down the flow temperature, save yourself money and have a more comfortable house.  

 

Unfortunately the manufacturers of controls have, over the years, seduced us into thinking that micro zoning in time and space saves money and is somehow desirable or necessary.  Even with a boiler (and excepting very lossy or very long and thin or otherwise oddly shaped houses) this is unlikely to be true, and is certainly not true to the extent we have been told by those with a vested interest in us buying their products.  With a heat pump (admitting the same exceptions) it's almost definitely not true.

 

Likewise ignore me if you wish!

Edited August 25 by JamesPa

[connick159]

Does anyone know the required steps to "unpick" a setup where the UFH8 wiring center and stats in every room have been installed?

Is it a simple matter of removing actuators or do you meed to do something else? 

[JohnMo]

Simple way is remove actuators. Set target temp in any room to max, so you always have a call for heat, this will ensure pump on manifold runs, or just join the call for heat wires together if there is no pump. Use the room stats as an easy reference room temperature for the next bit.

 

Open all the manifold flow meters to fully open. This will allow the ASHP to work at target dT without fighting the closed meters. Any room that is always hot trim down the flow to the loops in that room. If all rooms are hot, trim ASHP target temp on the WC curve.

Edited September 4 by JohnMo

[JohnMo]

After you have done that you need to address a few other things to get best efficiency.

 

Assume a mixer valve and additional pump are on manifold, look to remove them so you can operate on WC. The mixer will always add distortion to system as there is always mixed in return water to flow.

 

If you have a buffer you need to delete or ideally modify to be a volumiser on the return line only.

 

Then look at your circulation pump logic. You need to it switch on off with the ASHP compressor, not be on 24/7.

 

Look at you 3 way valve that diverts flow to cylinder or heating, check make and model, then find kvs value from manufacturer datasheet. You for a kvs no lower than 6, but the bigger the number the better, if 10 or above that is great.

 

Strainers in system, replace with a low pressure loss central heating filter. Strainers have a pretty huge pressure loss, ball valve strainers are the worst.

[Kelvin]

I was chatting with a Mitsubishi service engineer a few weeks ago. He was telling me that Mitsubishi are seeing premature failure of their compressors (at around three years) due to zoned system setup short cycling. So much so that they are considering extending their service agreements to include the UFH side but only if they can undo how the systems are setup which is similar to the above. They really ought to be educating their official installers on how best to install their systems to avoid this problem. 

[connick159]

On 04/09/2025 at 08:21, JohnMo said:

After you have done that you need to address a few other things to get best efficiency.

 

Assume a mixer valve and additional pump are on manifold, look to remove them so you can operate on WC. The mixer will always add distortion to system as there is always mixed in return water to flow.

 

If you have a buffer you need to delete or ideally modify to be a volumiser on the return line only.

 

Then look at your circulation pump logic. You need to it switch on off with the ASHP compressor, not be on 24/7.

 

Look at you 3 way valve that diverts flow to cylinder or heating, check make and model, then find kvs value from manufacturer datasheet. You for a kvs no lower than 6, but the bigger the number the better, if 10 or above that is great.

 

Strainers in system, replace with a low pressure loss central heating filter. Strainers have a pretty huge pressure loss, ball valve strainers are the worst.

Thanks heaps for the info. Not sure if i habe a buffer or its just an expansion vessel.

Also, not sure what a strainer is but all the other stuff makes sense. I have manual mixing valves on both manifolds and pumps on both manifolds too. Not sure if i need them but the UFH guy installed them as standard. We had one guy do the ufh and screed and another mob do the ashp. Looking back, should have gone with the one mob.

Thanks again.

[JamesPa]

On 04/09/2025 at 09:01, Kelvin said:

I was chatting with a Mitsubishi service engineer a few weeks ago. He was telling me that Mitsubishi are seeing premature failure of their compressors (at around three years) due to zoned system setup short cycling. So much so that they are considering extending their service agreements to include the UFH side but only if they can undo how the systems are setup which is similar to the above. They really ought to be educating their official installers on how best to install their systems to avoid this problem. 

I suspect there are a lot of cases of ufh by one organisation, ashp by another so they are not designed together.  Ufh after all tends to be for new builds and by it's very nature is essentially part of the fabric. 

 

Thus it's almost natural to build a ufh system and later tack a heat generator on the side.  So ufh comes with lots of unnecessary controls so it could operate stand alone, which essentially needs to be bypassed if you are running it with a weather compensated heat pump or boiler. 

 

Based on cases I've seen here and elsewhere it feels like this is a significant part of the 'problem' (amplified of course by our obsession with micro zoning that the control manufacturers have ruthlessly nurtured over several decades).

 

Edited September 7 by JamesPa

[JohnMo]

1 hour ago, connick159 said:

not sure what a strainer is

A Y type looks like this

A ball valve strainer looks like this

This what removed and replaced with 

[JohnMo]

1 hour ago, connick159 said:

buffer or its just an expansion vessel

An expansion vessel only has one pipe connection.

 

Generally a volumiser will have only 2 connections and will be only on the return or flow piping.

 

A buffer could be 2, 3 or 4 connections, but will have flow and return piping connected to it.