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Creating a second zone on Mitsubishi Ecodan ASHP

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Air Source Heat Pumps (ASHPs)

Last Post by BryanB 1 year ago

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BryanB

(@bryanb)

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Topic starter 15/04/2024 9:52 am

I am trying to set up a second zone with my Mitsubishi Ecodan ASHP system. Zone 1 is the existing radiator circuit and zone 2 will be the new UFH in an extension. Zone 1 is controlled via the wireless programmer and zone 2 via a separate thermostat and separate pump.

I have the contacts from the UFH thermostat via the UFH wiring centre connected to IN6 (Room Thermostat 2 input) and the UFH Pump to OUT3 (Zone 2 space heating).

I have turned on DIP switches SW2-6 and SW2-7 but keep getting an L5 error (Indoor FTC temperature thermistor reading incorrect value, thermistor disconnected or wired into the wrong connection on the board, incorrect dip switch setting on the FTC board). The manual tells me I don’t need an indoor thermistor if I’m using the remote wireless controller. I have also tried changing SW3-1 and SW4-1 but still get an error code.

With SW2-6 and SW2-7 on, the controller shows 2 zones (Z1 - Z2) under the House symbol but then goes into the error mode.

What am I doing wrong? Any help much appreciated.

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Gary

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15/04/2024 4:48 pm

Do you have SW3-1 turned on that is required to allow the input from the 2nd thermostat.

mine is wired as 2 zones and if I had my time again I would wire it as 1 zone running off a single thermostat as a max temp cut off. If you have 2 zones that work independently the HP is more likely to cycle on and off due to low water volume to heat leading to poor efficiency and increased wear

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BryanB

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Topic starter 15/04/2024 5:14 pm

Thanks, Gary, - I've tried it with SW3-1 turned on - but still get the L5 error. I assumed that SW3-1 was purely to change the operation depending upon the thermostat contacts being normally open or normally closed.

There is also a statement in the installation manual that says "When Dip SW 4-1 is OFF, 2-zone temperature control and 2-zone valve ON/OFF control is not available." So I've changed SW4-1 as well, although in the table of DIP Switches it states that SW4-1 is for multiple outdoor units. I've also tried changing SW4-2 to set to Master - but in each case I get the L5 error.

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BryanB

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Topic starter 15/04/2024 9:10 pm

Posted by: @gary

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mine is wired as 2 zones and if I had my time again I would wire it as 1 zone running off a single thermostat

I take your point about a single zone -it has been running as a single zone but I'd like to try with more control. Also it has now become a challenge to achieve it!

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Derek M

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15/04/2024 9:14 pm

@bryanb

You may find the following video of use.

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Gary

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16/04/2024 10:59 am

Derek's video link makes a good point, what have you got the zones set up as in the FTC controller, if you are using the main FTC controller to measure room temperature to control the rads that should be set as main RC and if you are using a third party thermostat as the controller for the UFH for zone 2 that confusingly should also be set as main RC, if its set as anything else it will be looking for a signal from a Mitsubishi wireless controller that you don't have, that could create the error you are seeing.

This post was modified 2 years ago by Gary

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BryanB

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Topic starter 16/04/2024 12:12 pm

Thank you Derek and Gary. I'm using the wireless thermostat to control the temp for the rads and a third party one to control the UFH. So from the video it looks as if Zone 1 should be set to Room RC and Zone 2 to Main RC. I'll try that later. Thanks.

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Derek M

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16/04/2024 12:17 pm

Posted by: @bryanb

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Thank you Derek and Gary. I'm using the wireless thermostat to control the temp for the rads and a third party one to control the UFH. So from the video it looks as if Zone 1 should be set to Room RC and Zone 2 to Main RC. I'll try that later. Thanks.

The main point that I was making was the need to switch the controller off and then back on for DIP Switch changes to take effect.

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BryanB

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Topic starter 16/04/2024 1:59 pm

I had been doing that - the whole system was shut down between changes. But I hadn't made any changes to the main controller but it looks as if I can't do that without changing the DIP switches again to enable a second zone.

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BryanB

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Topic starter 17/04/2024 11:18 am

Still no joy! With SW2-6 and SW2-7 turned on I can see two zones and set Zone 1 sensor to be Room RC1 and Zone 2 to be mainRC (instead of TH1). However I am still getting the L5 error to do with the indoor FTC thermistor.

I've also tried with SW4-1 and SW4-2 turned on - as in the manual it states these need to be on for 2 zone control - but it doesn't affect the L5 error.

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Gary

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17/04/2024 11:54 am

Mine may be older and different but on mine SW2-6 is for a mixing tank and the manual states that SW2-7 only works if SW2-6 is off.

SW4-1 and SW4-2 on mine relate to using multiple outdoor units as master and slave and don't relate to multiple zones so these are also off.

This post was modified 2 years ago by Gary

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Derek M

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17/04/2024 12:48 pm

Posted by: @bryanb

↑

Still no joy! With SW2-6 and SW2-7 turned on I can see two zones and set Zone 1 sensor to be Room RC1 and Zone 2 to be mainRC (instead of TH1). However I am still getting the L5 error to do with the indoor FTC thermistor.

I've also tried with SW4-1 and SW4-2 turned on - as in the manual it states these need to be on for 2 zone control - but it doesn't affect the L5 error.

I suspect that you are getting an L5 error because under 'Room Sensor Settings' you are trying to allocate RC1 or MainRC to zone 2, whereas the device installed is actually a thermostat (On/Off device) rather than a temperature sensor (Thermistor). I suggest that you set Zone 1 to TH1 or MainRC and leave Zone 2 unselected.

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