Mitsubishi Ecodan 8.5KW one zone gone offline and missing from main controller

[petehuws]

Hello Experts,
hoping this is easy to understand.
Last year it was no problem, but this year we seem to have lost one of our Ecodan heating zones.
Zone 1, configured as Underfloor heating
Zone 2, configured as Radiators.

We have lost Zone 1 for the underfloor heating, zone 2 radiators and the DHW all work fine. The zones are controlled by Siemens RF100 RF thermostats, I have swapped the thermostat transmitters/receivers around but they don't seem to be the fault and when trialing the zone 1 thermostat, the moment the 'call to heat' comes on I can hear the relay in the receiver actuate closed and the green connection light on the receiver illuminates, when I spin the dial to 'call for no heat' I hear the receiver relay open, green led goes out, again I have interchanged the RF thermostat transmitters and receivers but the problem remains on the zone 1.
To add to the mystery, I think it has been missing since we had a service on the system, so suspiciously I think it has been erronously disabled.
I have tried to get the technician back for some time now but is ignoring my calls and messages. On our system we have the main remote controller yet it only looks as if the one one is active. I have been through the ROOM RC ZONE SELECT settings but I never seem to have the option or control of a second zone.
I can't be sure but have a feeling the problem is with the setup rather than a failure, any ideas or an Engineer to visit and set would be most welcome. postcode CH7. Many thanks for any advice. Kind regards

 

[SJB060685]

Has the zone valve been checked etc?

 

[petehuws]

Hi SJB060685,
Thanks for the reply, I don't believe it has. This would be the zone flow valve I assume?
Many thanks

 

[SJB060685]

Yes, I'm assuming you have a two port valve for each zone, UFH, Rads and DHW. Each zone will be controlled by a programmer and thermostat. Really this needs a multimetre and an understanding of the components to safely and correctly test.

 

[petehuws]

Thank you, I'm a qualified Electronics Engineer, but I'll probably still look to get somebody around who knows better than I then.
All the very best

 

[SJB060685]

If you're a qualified electrician then you're more than capable. Do you have a wiring diagram for system? What I'd be looking for is testing UFH zone valve function, see if you're getting feed to it from thermostat and after that.

 

[Brambles]

It is unlikely that a service engineer has disabled a heating zone. You can only disable zone 4 and above with a 8.5KW Ecodan. The base configuration is 3 zones - 2 heat zones and 1 dhw into the The Main Board (FTC2). If you have one heat zone functioning, test the second zone by changing over J3 J4 (thermostats) and or J9 J10 (zone valves). If it is the board that has failed, I would involve MHI, it is an expensive item to replace and is electronically matched to the serial number of the ASHP. If it is the external units that have failed it is a simple like for like replacement.

I am sure that you are aware that zone valves for an ASHP need to be fast acting and are not configured in the way you would for a gas or oil fired system. The thermostat and associated zone valve are wired independently into FTC2 or any associated extension module. This is in part to ensure that the zone valve is confirmed to be fully open before the ASHP is activated.

During any troubleshooting on the problematic zone, ensure that you do not trigger the ASHP will all zone valves closed. You can inadvertently do a lot of damage to the heat pump in a few minutes.

 

[petehuws]

Thank you,
I've taken a look at a high level wiring diagram & it looks quite simple, I'll go do that & check the I/O of the valve & report back.
Thanks v much.

 

[SJB060685]

It is unlikely that a service engineer has disabled a heating zone. You can only disable zone 4 and above with a 8.5KW Ecodan. The base configuration is 3 zones - 2 heat zones and 1 dhw into the The Main Board (FTC2). If you have one heat zone functioning, test the second zone by changing over J3 J4 (thermostats) and or J9 J10 (zone valves). If it is the board that has failed, I would involve MHI, it is an expensive item to replace and is electronically matched to the serial number of the ASHP. If it is the external units that have failed it is a simple like for like replacement.

I am sure that you are aware that zone valves for an ASHP need to be fast acting and are not configured in the way you would for a gas or oil fired system. The thermostat and associated zone valve are wired independently into FTC2 or any associated extension module. This is in part to ensure that the zone valve is confirmed to be fully open before the ASHP is activated.

During any troubleshooting on the problematic zone, ensure that you do not trigger the ASHP will all zone valves closed. You can inadvertently do a lot of damage to the heat pump in a few minutes.

So Brambles what is different about an ASHP zone valve to say an ordinary Honeywell for example on oil or gas?

 

[Brambles]

For an Air Source Heat Pump to maximise efficiency you want unrestricted flow. That is not always practical in smaller installations. When you have valves, they must be fully open before the ASHP is triggered. Normal Valves that operate a micro switch are (can be) too slow and damage or trip the pump very quickly. The way round this is to configure the valves through a central controller that opens the valve first, pauses, checks it is open from the micro switch signal then triggers the ASHP.

Does that make sense?

 

[petehuws]

Hi Brambles, thanks a bunch.. That sounds like a good way to go, in effect I've done the J3 /J4 thermostat swap, swapping around the zone valves is what I want to do, I'll isolate the ASHP whilst I do, & bring back online after the exchange, I'll check the I/O signals to/from the suspect valve before I do.
Many thanks

 

[SJB060685]

That makes complete sense Brambles, thank you. So could you use a Honeywell two port for example and it's just the PCB that checks for end switch signal before then bringing on ASHP? Also could either you or petehuws upload a detailed wiring diagram for ASHP and multiple zones just so I cant have a look and further familiarise myself.

 

[Brambles]

SJB,

Heat pumps are at their best when run continuously. The output is generally fixed or modulated slightly by the use of an inverter - so any form of downstream control has a negative impact on the performance. With gas or oil downstream control improves performance and efficiency.

So from the heat pump we need to use all the heat it delivers. Buffer tanks (properly sized) are very good at allowing the heat pump to run continuously whilst controlling the down stream zones with conventional Honeywell Valves operated in a normal fashion.

The challenge becomes harder when there is no buffer tank and radiator systems are included. In these circumstances as a minimum, the first control valves must be fully open before the heat pump is triggered. Often the volume in the radiator zone is too small to satisfy the heat pump alone and requires a second zone ( normally dhw) to be activated too.

In the MHI system (Ecodan) the heat pump controls this through a central module of three zones, with the ability to add a further 6 zones. The controller will take its instructions from the thermostat inputs to each zone, but if that flow demand is insufficient for the heat pump, it will override the external inputs and bring in a second or third zone for a period whilst the system stabilises. That is why in the Evodan you cannot delete the three core zones.

The reasoning behind this is that it is much harder to set up and operate a small ASHP system than a very large one. On the latter you have plenty of options for using surplus heat. The worst systems are small domestic ones where the ASHP has been oversized - thinking that it is a good thing to have - it isn’t!

For background NICEIC do a good Heat Pumps Learners Guide - don’t be put iff by the title it is a well written in depth guide to Heat Pumps in an understandable format. Thereafter look a the technical guides from Panasonic - which are fully configurable units.

The MHI (Ecodan) technical guides are quite limited. The MHI system is easy to set up, but difficult to configure - you need to be accredited by MHI to have access to the codes - which change every 9 to 12 months.

If you need any more detail or explanation please get back to me.

 

[SJB060685]

Again thank you Bramble, you clearly know your stuff , I enjoy reading your knowledge but you didn't answer my question or maybe I didn't ask it right. Without a buffer tank and just zones wired into the command unit can you use typical Honeywell two ports or does it have to be a specialist valve certified for ASHP that does everything you mentioned above ie. Checked to see is fully open before engaging pump? As I said in another post I have a Daikin ASHP in my flat with rads and cylinder with what I was told is a diverter valve, one I'm not familiar with as I'm not ASHP trained. I have attached an image

 

[Brambles]

In essence, yes you can use Honeywell or other 2 port valves - but have in mind you need to configure them to be fully open before the ASHP is triggered. However, that is not the case for Honeywell 3 port valves.

The valve that you have shown in your picture above is a three port mixing valve - you cannot (easily) replace this with a three port Honeywell Valve. If you do, you may (depending on the Honeywell Valve type used and how it is wired) get mixing of the DHW and Heating Zone flows. If you want to use a Honeywell as a direct replacement only use a Honeywell spring return valve (V4044C) not a mid position valve. It also needs to be wired correctly to ensure full separation at all points during operation.

If I was asked to replace said valve I would give the Customer a choice - the Daikin recommended valve ( cost circa £300 - I think) or Honeywell at £70

I think that this valve was manufactured by or for Daikin to eliminate problems experienced by the use of Honeywell 3 port mid position valves - I may have dreamt that bit. However, when you see the price difference, you can understand why people gave it a go! In essence any valve you use as a replacement for the one in your photo must have total separation at all times of the DHW and Heating Zone flows.

Hope that helps, has that answered your question properly?

 

[SJB060685]

Yes that answered my question Brambles, thank you. One last question then I'll leave you alone. Say someone used a Honeywell 2 port for each zone on an ASHP, how or what happens in the control unit to ensure the valve is fully open before engaging the pump? Surely the typical 2 port with end switch that only energises when valve is fully open is enough?

 

[quality]

I don't agree with damaging the heat pump if a zone valve doesn't respond quick enough to allow full flow. I do agree with full flow being required so as to allow correct output form the heat pump. If there is a buffer installed it doesnt matter what type of zone valve is used so long as it works.

 

[Brambles]

Generally, it is a time delay either 50 seconds after the power is supplied to the valve or 20 seconds after the micro switch closes. A decent valve should be fully open within 12 seconds

We do a 12kw High Temperature Heat Pump that will deliver flow at 65 degrees C - that has to operate through a buffer.

If you look at the warranty conditions of most reputable heat pumps valve arrangements and buffer sizing is covered in some detail.

 

[SJB060685]

Thanks Brambles. A time delay was one way I was picturing it done

 

[petehuws]

Hi Gents,
Solved the missing zone 1 UF heating, had a bit of time this morning & the problem was away from the heat pump. A failed shut Danfoss HPA2 actuator valve ahead of the remote pump in my attic. Both the pump and valve are energised by a shared relay which closes when the call to heat comes along, powering the pump & energising the Valve to open. I've manually opened the valve & have flow through to the pump and now to the floor. Should of really suspected the weakest part first.
As they say though "The fix is always the last thing one tries"..
Merry Christmas all.

 

[SJB060685]

Merry Christmas to you. Glad you've found the culprits

 

[petehuws]

Merry Christmas to you. Glad you've found the culprits

Thank you very much - you were the trailblazer that set me on the path... All the very best
Pete

 

[SJB060685]

No worries my friend, although I set you on your path Brambles superior knowledge taught me a couple things I didn't know, so thank you to both of you.