Another st699 to hive thread

[OwainOW]

Hi all,

Sorry to add another thread but I’m looking for some help. I have installed a hive v3 water and heating replacing my old st699. This was prompted by removing the old thermostat that I thought wasnt working and doing nothing to find it was infact setting the heat of the house and plunged me (and begrudging partner) into a cold house situation. I decided to install a hive as I had been considering it for some time and followed the post of someone with similar wiring to me on this thread (https://www.diynot.com/diy/threads/honeywell-st699-to-hive.469769/) however there is a slight difference that my setup as seen in the image had two lives going into number 8 on the st699 one seeming to be connected straight to the boiler. [GALLERY=media, 107727]5977727D-3A7A-4F15-A60B-AFFDF6025DFD by OwainOW posted 28 Feb 2022 at 9:06 PM[/GALLERY]

I then after some trial and error added it to slot 3 on the hive and had the hive on with the boiler active too. Wiring shown below
[GALLERY=media, 107728]6F4E6BDA-6F85-4E62-A7BD-E0AA8C8F08CE by OwainOW posted 28 Feb 2022 at 9:06 PM[/GALLERY]


I thought the job was done however it seems that the heating still won’t come on… can’t tell if the hot water is working as when I turn the shower on it is hot but we do have a hot water tank. Any help would be appreciated I can’t see where my wiring is wrong but as you may have gathered this isn’t my strong suit.

many thanks

 

[OwainOW]

Whether it’s relevant or not I’m unsure but this cable where the thermostat was is still live. [GALLERY=media, 107729]Image by OwainOW posted 28 Feb 2022 at 9:50 PM[/GALLERY]

As I mentioned we had an old thermostat here which didn’t seem to actually do anything until we took it off and now the heating won’t work. Would it still be live even with the hive controller installed?

 

[stem]

The wires at the Honeywell ST699 move to the Hive terminals that have exactly the same function. Where there are two wires in a terminal both wires make the transfer and stay connected together.

You don't need the loops that the ST has between L, and its terminals 5 and 8. Hive has these connections internally already for you.

The old room thermostat can't simply be disconnected as this would leave the heating wiring 'open circuit' and the heating will not operate, so, the two live wires that used to go to the thermostat then need to be joined together to complete the circuit. This can be done where the thermostat was by putting them in a junction box, or at their origin, and then the old thermostat cable can be disconnected completely.

A note of caution though: some thermostats have a neutral connection and this should be isolated and obviously not connected to a live wire. The problem is that sometimes with thermostat wiring a blue or black wire is often used for one of the live connections. If you are unsure of anything, post back details of the old thermostat and what wires were connected to its terminals and someone will be able to assist.

 

[OwainOW]

Hi,
Thanks for the reply it does seem that the thermostat is the issue then as the hive wiring seems correct. It seems there is only one live cable although obviously I can’t be sure as you mentioned the neutral is actually a neutral but the live is definitely live. I have attached a photo of my old thermostat a Switchmaster SRT 2. [GALLERY=media, 107730]Switchmaster SRT 2 by OwainOW posted 1 Mar 2022 at 9:13 AM[/GALLERY]

I actually thought it was dead when I took it off so
I didn’t photograph the wiring but as you can see there are two cables in plus the earth which is then represented by my photo below
[GALLERY=media, 107731]F66DADC3-37BE-47A5-9B20-A41249C815AC by OwainOW posted 1 Mar 2022 at 9:15 AM[/GALLERY]of the current 3 wires in the wall with the (neutral maybe?) with its box off but as shown in the photo previously all were just wired into seperate boxes. Any idea which to connect to get the circuit closed again?

thanks for the help so far

 

[OwainOW]

Solved - that was exactly it that neutral is a switch live. Thanks for the help. The only other caveat in case anyone Is in a similar position to me is that the wiring on my hive required the heating to be connected to the boilers (switch?) live as opposed to the hot water as I have seen with others. Working wiring is below.

[GALLERY=media, 107732]Image by OwainOW posted 1 Mar 2022 at 9:46 AM[/GALLERY][GALLERY=media

 

[stem]

Well done glad you got it sorted. Thanks for taking the time to post back how it went.

It's often the case that a standard cable L, N, E is used to connect a room thermostat and the N conductor is often used as the switched live. It should really have a brown sleeve over it (or red in the case of older installations) to indicate that it is being used as a live, but not all do, as you have discovered.

Not sure what you mean by:

the wiring on my hive required the heating to be connected to the boilers (switch?) live as opposed to the hot water as I have seen with others.

However, the ST699 has two simple switches inside, one for heating and one for hot water, and so does the Hive. From an electrical point of view they are the same, so you are simply exchanging one switch for another identical one. For exchange purposes, what's on the other end of the wiring is irrelevant really, provided that the ST699 was installed and working correctly in the first place.

As you have a 3-port motorised valve connected [the clue is that there is a wire connected to the HW off terminal] then inside the motorised valve is a microswitch that controls the boiler when the heating is required, which means the Hive won't be controlling the boiler directly. Hive controls the motorised valve, and when the valve is in the central heating position that fires the boiler.

The old room thermostat becomes redundant because the Hive has both time and temperature control built in, unlike the ST699 which just provides time control.