Have I Wired This Wrong? Honeywell T3 Replacement
I have wired it as per the instructions on the app. But my radiators don’t seems to be heating up. I’m just wondering if I’ve wired this properly as I wasn’t sure if I was supposed to connect the wire with the dotted line circle or not.
Any advice would be appreciated.
Here’s the Honeywell T3 wiring.
https://i.ibb.co/KyLPPDZ/0-EAD5706-3192-4-F53-A689-EE4-DB105-CEB2.jpg
And here is the wiring diagram from the app that I have followed. Am I definitely supposed to have both wires going into NO and NC?
https://i.ibb.co/wBMgLr8/53-C8-A1-D5-0-DBC-47-C0-B631-A3628-ACCE880.png
Thanks again!
Answers
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I don’t know much about district heating but try just COM and NO.0
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Depends on what the wires are actually used for, and the colors aren't too clear, looks like the wirres are one color but taped over in another. I would think twice before putting a blue wire (normally used for return/neutral) on the NC contact. Normally you'd just have Brown (Live) on COM, and Black (Switched Live) on NO. Park the blue wire. If it is neutral you'd probably fry your relay.
But it could be that the T3 is switching A between B and C, and one combination pulls something open while the other closes it...
Worth using a continuity tester of some kind (battery and bicycle light if nothing better) to measure what the T3 actually does. The picture I found had just a NO relay between A&B with C seemingly isolated, but maybe that was a simplification...0 -
Thanks all.
Here’s a link to the wiring diagram for the HIU.
https://i.ibb.co/bmhwBR3/F8-B769-A5-BA23-4150-989-E-47-D2811-DB023.jpg
And here’s a link to the diagram on the Honeywell Thermostat.
https://i.ibb.co/ZNhSbDv/A848-BDFC-5-AC7-4067-B810-A08-DFAE51-B5-C.jpg
Does that help give a better idea at all?0 -
@Patty37 you can follow the wiring diagram provided by Tado in your first post. The C terminal on the Honeywell thermostat is NC, but I have no idea why somebody has sleeved the wire in blue (indicating Neutral). @luteijn is correct to be cautious, but I'm pretty sure if that current device is a T3 then you'll be fine. The T3 is battery powered and there just isn't a valid reason for using a Neutral.
When testing make sure you can hear the thermostat relay click on and off when you make changes in the app.
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Looks like it’s working intermittently. The heating will be on. Then all of a sudden it will be off and radiators cooling down despite being on in the app. Try and turn heating back on on the thermostat and via the app and there’s no clicks and no heat going into the radiators.
Could it be a case or something tripping in the HIU?0 -
Like other smart thermostats Tado is a TPI thermostat, so it will modulate the heat on and off to reach the set point. Whereas older thermostats tend to be all on until the set point is reached. In the app when you tap on the room and a pop-up appears there should be up to 3 squiggly lines next to the temperature. If all three lines are there then I'd expect the heat to be on for most of the time. If there's only one line the heat will be on for less than 33% of the time.
One way to force the heat on for a long period is to use the boost feature in the app. If this doesn't keep the heat on, then it may suggest there is a problem with controlling the HIU.
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On further investigation the relay clicks, the Tado trv does its thing. The radiator warms slightly but after 5 mins is cold again and I don’t hear the TRV closing.
So I’ve had a look at the wiring box on the HIU to see if it ties up with the diagram in the HIU’s manual. I don’t see any wires that seem to go to the thermostat. Jeez. At a loss here.
HIU manual: https://i.ibb.co/cytQXXf/34-C8800-A-BC6-B-4424-A14-C-2-F65-FE9867-EB.jpg
Physical wiring inside HIU: https://i.ibb.co/ZYDH1kD/B13-B41-F6-709-E-4081-B736-1-B5-A3-A6714-E5.jpg
https://i.ibb.co/1Lf325T/7-D9-B6477-AA23-4-BD0-8813-F3-AE9-DB1613-D.jpg0 -
Have you tried removing the Tado TRVs and running the system with just the wall thermostat? The controller at the top of the HIU has a number of temperature probes measuring water temps in the pipes. I'm wondering if the Tado TRV heads are triggering a condition where the HIU switches off due to incorrect flow through the system.
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So looks like it’s a TRV problem maybe. I’ve put on the original TRV’s. Opened them to full setting and the radiators are heating up and filling. All the zones in the app are turned to off at the moment. But I guess that won’t matter as they are technically then Tado Smart TRV’s anyway.
Do you have any idea how to fix the TRV’s by any chance? Seems pretty redundant having the system if I can’t use the TRV’s.0 -
I have no experience with HIUs, but I do know these units will stop water that is too hot from returning to the district heating network. For efficiency reasons the main heat source needs cooler water returning from each property. I suspect the HIU controller is shutting down the flow of water when the TRVs are fitted. Do you have TRVs on all radiators? Perhaps try adding/removing Tado TRVs until the system works.0
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On further inspection of my wiring diagram, the wiring box in the HIU and the Tado wiring.
There only seems to be Switch Live, Neutral and Ground wires connected to the terminals in the wiring box in the HIU. The L1 terminal which is to house Live wires hasn’t got anything in them. Neither from the fused spur or the Tado. Is that what could be causing the problem?
I’m assuming because the radiators heat up as soon as I open the TRV’s the HIU is constantly on.
Thinking at this point I may need to try and find a local professional who can deal with HIU’s and asking them to install properly.0 -
very similar issue, heating is suppose to be on but temperature drops.
any ideas .?
for me it happens when trying to heat only one room mainly
.Very similar issue
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