Hive install gone sideways, advice needed!

[wrathalanche]

Hi all,

I am trying to install a Hive receiver to my boiler after a colleague at ensured me that it was a doddle. I'm handy enough to get most things done around the house, but typically when I find myself unsure of how to complete something correctly, I aways end up making a totally wrong decision.

My boiler is a Vokera Sabre 24 (combi). Link to install manual here:
https://letsfixit.co.uk/wp-content/uploads/SABRE.pdf

Standard controls wiring diagram on page 14, wiring for adding external controls on page 31, circuit diagrams follow on from there.

Basically the boiler has no thermostat and the CH just fires up based on the settings on a mechanical timer.

Although figure 28 on page 31 shows how a stat should be installed, this didn't make much sense to me and i completely ignored it, and instead installed it basically exactly like figure 28A, treating it like an external timer.

In my head, both the timer and the hive receiver would need power, and the switch on the timer would need to remain connected, so that the timer could be switched to "permanent on" and then hive would do it's thing based on the stat and the app. So I had the hive receiver plug into the same terminals on the block as the timer:

Permanent L came from the 4th terminal in the block to the L pin on the Hive receiver.

Permanent N came from the 6th terminal to the N pin on the Hive receiver.

The first terminal block I interpreted as N/O, so this went to the CH on pin on the Hive (pin 3).

I took the third as N/C so connected that to CH off on the Hive (pin 2).

"Common" confused me, so based on advice i had read elsewhere, i settled for making a link between the L pin on the Hive and pin 1. As i understood it, this meant there would be 230v going to common via pin L. Made sense to me.

So to be clear, all the connections into the boiler terminal block shared this space with the existing timer connections.

Also i couldn't get 4 core cable, so i used two lengths of T&E. One for the voltage and one for the switching. This meant i had two earths each end. Both went into the Hive earth terminal, and onto the ground stud in the boiler.

When i turned it all on to test, the boiler came on with a blinking green LED indicating it was on standby (the timer was in an OFF time slot). I switched it to permanent on, and the Hive came to life with a blinking amber, and from the silence in the boiler i could tell the CH hadn't activated. This was exactly what I'd expected.

To test the wiring, the Hive manual then states to press the CH button on the receiver, which should cause a green light to appear on the Hive. When i did this the green appeared for a split second before the boiler completely died. No bang, no pop. I have found that fuse 2A as shown on page 31 of the install manual has blown. I'll head out tomorrow to get some new ones and hopefully bring the boiler back to life. I have removed all the Hive wiring for now.

So what went wrong and why? I assume it's because:

a) i was ignorant of the meaning of the requirement for voltage free connections on the Hive (which i understand the single channel hive is suitable for - i just don't know if i achieved them),
b) because i did not fit as instructed in figure 28. This set up confuses as i don't understand how the Hive is powered. The line marked "common" has no connection to the 230v from the spur and i don't understand how i can wire into the Hive directly from the old timer. Does this mean the Hive can run without a connection to permanent L and N?
(This poster seems to insinuate he completed a successful install in similar circumstances using only two wires and removing the timer wiring completely: https://www.diynot.com/diy/threads/hive-2-compatibility.456664)
c) because i doubled up the terminal connections with the timer's.

Any advice from the experts?

 

[picasso]

Connecting common to live has put 240vac on the volt free connections and has probably done your pcb.

 

[DP]

Is the hot water working?

 

[wrathalanche]

In work this morning and spoke with the electrical guys who have summed up pretty much what you said picasso, and makes total sense.

Of course what i should have done is wire the first terminal to common, CH On to NO, and left out CH Off. Permanent L and N as i had it, and just removed the existing timer wiring completely.

I've found a source for the PCB online for £60 so will consider it an expensive lesson if the fuse doesn't sort it (losing hope now).

DP, no hot water as there's no power to the boiler at the moment because of blown fuses/blown up PCB.

 

[Madrab]

With any luck you have just blown the fuse and the PCB hasn't gone too, will only know when you replace the fuse. Just make sure the Hive is all disconnected before you switch anything on.

£60 for the PCB?? Make sure you get a warranty with it cause that sounds like a 2nd hand part.

Make sure you use fast blow fuses for it too.

Your boiler uses a volt free system so no power is to be sent down the switching circuit. So use terminals 1 & 3 on the hive receiver and - as you look at Fig 28A - the right hand connector block, counting from the left hand side - connectors 1 and 3.

Power the receiver either from the fused spur supplying the boiler or from the right hand connector block in Fig 28A, connection 4 = L and connection 6 = N.

 

[wrathalanche]

Madrab, cheers so much. It all makes sense now. Also thanks for the optimism, but unfortunately the PCB is indeed goosed. You put me off going for a suspiciously cheap deal on eBay - I'm guessing there's probably a load of refurbs going about. Found a branch outlet a few miles away so I'll pick up the new one and hopefully get it all sorted tomorrow.

 

[wrathalanche]

UPDATE: Boiler is alive again and Hive all wired up exactly as Madrab instructed. Everything seemed fine but a strange glitch has surfaced. Hopefully someone will be able to suggest a fix:

Now that the Hive is installed in place of the timer, whenever I run my hot water, my radiators heat up too, even though the CH is set to Off on the Hive. The water pressure is down a wee bit and is slightly cooler than normal, presumably because both systems are being provided heat at the same time. The boiler has a dial on the front which I can switch between CH & HW, Off, and HW only. Even when I set this to HW only, the radiators heat up whenever I run the hot tap. This is a brand new issue, and has only started since replacing the pcb/ fitting Hive.

I had it my head that there was a gravity fed mode on the receiver which may sort this, but it appears this is only on the dual channel version of Hive. I have the single channel as that is what is recommended for combi boilers. Is this likely to be a programming issue with the new pcb, something to do with the Hive wiring, or some other electro mechanical fault elsewhere on the boiler?

 

[Boiler buddy]

Sounds like a diverter valve problem if radiators are heating up with hot water only. Might be stuck in the middle. Is your hot water cooler than it used to be?

 

[wrathalanche]

Cheers for replying, bg engineer. I've been meaning to come back and put in an update. The problem was the replacement PCB (my boiler was so old and cheap it didn't even use a diverter valve). Got another sent out and that sorted it. A boiler engineer I was put in touch with said the Vokera boards can be janky right out the box from the merchants. Sees it all the time.

Anyway, as a bit of a postscript- because I had the boiler casing on and off so much recently, I noticed a load of rust on the chassis due to a weep on the cold water inlet. Said engineer came out to look at it and found umpteen issues with the rest of the boiler - flue, prv outlet not plumbed to anywhere etc etc. Bit of a horror story, so took his advice and had a new boiler installed today. Far happier knowing it's all gas safe, as I had no history on the old one.

 

[Boiler buddy]

Good move, Vokera have a useful life of about 10 yrs, Hive should be fine with any new appliance, sounds bad if PRV was never terminated right, but at least you’ve had a pro to fit the new one.