Hive dual channel voltage

[Jimmy27]

I have had Hive running for a few years now without any problems.
A Dual Channel Receiver SLR2c driving an Ideal boiler.

A few weeks ago, the boiler packed in, we're not sure why, it could have been the PCB or something else, but basically it wouldn't do anything even though power was being sent to it. It was over 20 years old so we decided to fit a brand new boiler.

The new boiler is a vitodens and we're using the Hive as an "accessory" providing switched live.
The new boiler however is refusing to fire up its pump. Upon checking the power, we can see that there is around 65V continually coming out of the HIVE receiver through the HW On connection. The HW Off is correctly showing 230V (since all we've done is power the Hive on and not told it to do anything yet), but this 65V coming out of HW Off is confusing.
Is this normal for the dual channel receivers, or is this indicating that it's broken?
I wish I'd checked this years ago when we installed Hive. Maybe this is normal and the old Ideal boiler wasn't as sensitive as the Vitodens? Maybe this is a broken Hive and this is what broke the Ideal boiler??

Could someone else check their Dual Channel Hive Receiver and see what voltage you're getting?

 

[RandomGrinch]

HW Off is correctly showing 230V (since all we've done is power the Hive on and not told it to do anything yet), but this 65V coming out of HW Off is confusing.

In the Hive there is a relay that switches the live between HW On and HW Off.
With the HW Off, 230V should come from terminal 1. Due to the nature of the relay, there would only be a very small probability of any voltage coming out of terminal 3.
It is far more likely that the 65V is being back fed from somewhere else in the wiring centre.

I presume you have a Y plan system, if you have a connection to HW off?

Did the boiler installer check the controls worked, before they left?

 

[Jimmy27]

Yes, it's a Y plan system. The installer couldn't commission the new boiler because of this voltage coming through the switched live continually.

I've just checked the Hive voltage on each connection with everything else disconnected (cyl stat, frost stat, pump etc).

Connection/State	HW Off, CH Off	HW On	CH On
1	235V	65V	235V
2	235V	235V	0V
3	65V	235V	65V
4	65V	65V	235V

It looks like the Relay has given up the ghost and is not completely switching?

 

[RandomGrinch]

It looks like the Relay has given up the ghost and is not completely switching?

May be, but that sounds very odd.

What I would do next, is take the Hive out of the equation completely. After all, It is only a switch - we can replicate it's function by making links on the backplate (safely isolate the circuit before making changes)...

Test Hot water:
With a short wire link, connect L and terminal 3
Test HW + CH
Link L and terminal 3 & terminal 3 and terminal 4
Test CH only
Link L and terminal 1 & terminal 1 and terminal 4.

If the system works correctly with these links in place, the Hive has to be at fault.

 

[bernardgreen]

The measurements of 65 Volts may be due to stray capacitive coupling in the Hive and the use of a meter with a high impedance.

 

[Jimmy27]

Sorry for the silence... but after exhaustive testing you guys are right. Just by linking terminals and taking the Hive out of the equation and I see the same voltage being shown on supposedly "passive" connections... which means it is absolutely capacity coupling on the wire and the meter I'm using have a high impedance. (I now have an additional Hive that I bought of eBay that I don;t need ).

 

[Jimmy27]

Further update, and a question.
Having rewired the boiler and controls to come off an almost dedicated circuit (an existing circuit with only 1 double socket on it) the stray voltage still shows up due to the capacitive coupling on the SwitchedLive link running back to the programmer. Noting what people have said here and elsewhere, I decided to see if this Voltage was actually carrying any power... connected a lamp to the circuit.. no light (so no Amps).

So now I've added the boiler to the circuit, and the stray voltage is now carrying power.
Looking at the boiler wiring... I am curious about the DPST switch on the Vitodens itself.
I can't find any documentation for this wire on the internet, but the connections are (excuse the ascii art):

LoadLive-----------|------LoadNeutral
============|===============
SupplyNeutral-----|------SupplyLive

Does that look right? (it doesn't to my simple brain.. but I don't want to change it and risk breaking something if it's supposed to be like that).
I can't even find a replacement partnumber for the DPST switch to look at the datasheet.