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Creating a second zone on Mitsubishi Ecodan ASHP

BryanB · 2024-04-15T08:52:48Z

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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BryanB

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Topic starter 17/04/2024 1:20 pm

Gary -in the installation manual I'm looking at, on p26, 5.3. Functions Settings, under SW2-6. (mixing tank) it states that when SW2-6 is off 2 Zone temp control is not available! And under SW 4-1 multiple units (which I don't have) it states that when SW4-1 is off 2 zone temp control is not available. I'm getting very confused!

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BryanB

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Topic starter 17/04/2024 1:22 pm

Derek - thanks for that. Zone 1 was set to Room RC1 (I assume that's because I have the wireless thermostat ). I've changed it to main RC to see if it makes any difference but I can't leave Zone 2 unselected. It has to be TH1, MainRC or Time/Zone. I've tried all of them.

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Gary

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18/04/2024 6:56 am

@bryanb There are known to be mistakes in the manual, so don't treat it as gospel, afaik SW2-6 is if you have a mixing valve to have different temperatures in the 2 zones so hotter rads and cooler UFH, if you dont have that it should be set to off. SW4-1 is definitely if you have more than one outdoor unit this is nothing to do with 2 zone control so again I think is a mistake in the manual and both SW4-1 and SW4-2 should be set to off.

SW1-8 should be set to ON if you have a wireless controller, presumably that is the case and by wireless controller I mean this.

If the above controller is on zone 1 that should be set to RC1 and if zone 2 is using a 3rd party thermostat should be set to main RC.

This is the main RC.

I'm not sure any of these changes will impact the error you are seeing but its worth a shot.

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BryanB

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Topic starter 18/04/2024 12:47 pm

Thanks for your time with this Gary. I have a wireless controller running Zone 1. Sounds like the manual is more of a hindrance than a help! Your comment re SW4 1& 2 make sense.

I think though if I didn’t have SW2-6 on it gave me an LL error which was to do with incorrect DIP switches. I’ll check all that again when I clear out the airing cupboard to get at the control box.

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BryanB

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Topic starter 30/04/2024 10:18 am

Had another go at this, the morning. With SW2-7 ON it gives me a flashing LL error at the top of the main controller, but it still appears to run normally. However it does not seem to set up a Zone 2. The bottom left button on the controller is still marked "I" and I cannot set up Zone 2 room sensors. If I turn on SW2-6 I don't get the LL error and can set up Zone 2 settings - left button on controller marked as "Z1 or Z2". But then after several minutes the L5 error comes up and everything shuts down.

I guess if I turn on SW2-6, it's looking for a mixing tank(which I don't have) but presumably would have a thermistor which it can't find, hence the L5 error. I have what I think is called a low loss header, but that's hardly a mixing tank, with no temp sensors.

Not sure where to go from here!

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