Hive heating & hot water install wiring help with existing CH thermostat

[ChrisGG]

Hi, hope someone can help me out.

I'm installing a Hive central heating and hot water control replacing a Potterton EP2002 and Danfoss CH thermostat. I'm struggling to find where the CH thermostat is wired back to so I can remove it completely and bridge the connection. I cant find the connection to the CH thermostat in either of the two wiring boxes. I'm wondering if there is a work around? Or if I'm missing something?

Current system consists of:
Potterton EP2002 / Danfoss CH thermostat.
CH wiring box connecting boiler, circulating pump, myson power extra valve, connection onto HW wiring box.
HW wiring box connecting Honeywell 2 port valve, HW cylinder thermostat and connection from CH wiring box.
I've added photos of all the above and wired connections marked with text boxes.

Replacing the Potterton EP2002 with the HIVE receiver seems pretty straightforward. As per the photo:
EP2002 terminals 3 & 4 directly replicated to Hive 3 & 4.
EP2002 terminal 5 to Hive live and bridging wire removed (Hive does this internally). Neutral and earth wires to the same in the Hive.
EP2002 terminal C wires connected together in a terminal block separate to the Hive receiver.

Locating the end point of the CH thermostat cables is doing my head in. There must be a connection somewhere I can't find. Don't understand why it wouldn't be wired back directly to the CH wiring box. Unless I cant see it!?

Thanks for your help in advance.

Cheers,

Chris

 

[Johnmdc]

I think that it is the brown wire in 4 at the ep2002 and the earth wire (which has been used as a switched live) in C.

So disconnect both of these and put the grey wire that is also in C to 4 on the Hive.

 

[ian1182]

There are several items to look at

On the EP2002 you have

terminal L with link to 5, also in 5 is another brown core.
terminal C with a grey & green/yellow connected together

For the Hive
connect both browns from EP L & 5 into Hive L having discarded link brown (L->5)
connect EP N into Hive N
connect EP #3 into Hive #3
connect EP #4 into Hive #4
connect the pair of green/yellow cores into earth tether on Hive. Note keep the green/yellow in EP terminal C completely separate.
nothing in Hive 1 or 2

connect together in a terminal block the pair of wires previously in EP terminal C

As for the thermostat, easiest at this stage is just turn up to max pending locating the wires -or- just put the pair of cores at the thermostat into a common connection on a terminal block.

Do you have a multi meter. You can then check if the brown in EP #4 or #5 is the same as seen at the thermostat. Likewise is the green/yellow the same as seen in EP #C. Looking at the pictures I cannot spot the rogue green/Yellow from the EP terminal C. Certainly needs some investigation.

Based on S-Plan wiring the output from Hive#4 should go to the roomstat and then when demanding heat back to live input for the CH 2-port valve.

 

[ChrisGG]

I think that it is the brown wire in 4 at the ep2002 and the earth wire (which has been used as a switched live) in C.

So disconnect both of these and put the grey wire that is also in C to 4 on the Hive.

Thanks for the reply much appreciated.
I'll give that a try. Makes sense those wires connected to the thermostat.

 

[ChrisGG]

There are several items to look at

On the EP2002 you have

terminal L with link to 5, also in 5 is another brown core.
terminal C with a grey & green/yellow connected together

For the Hive
connect both browns from EP L & 5 into Hive L having discarded link brown (L->5)
connect EP N into Hive N
connect EP #3 into Hive #3
connect EP #4 into Hive #4
connect the pair of green/yellow cores into earth tether on Hive. Note keep the green/yellow in EP terminal C completely separate.
nothing in Hive 1 or 2

connect together in a terminal block the pair of wires previously in EP terminal C

As for the thermostat, easiest at this stage is just turn up to max pending locating the wires -or- just put the pair of cores at the thermostat into a common connection on a terminal block.

Do you have a multi meter. You can then check if the brown in EP #5 is the same as seen at the thermostat. Likewise is the green/yellow the same as seen in EP #C. Looking at the pictures I cannot spot the rogue green/Yellow from the EP terminal C. Certainly needs some investigation.

Thanks for the reply much appreciated.
Appreciate the confirmation on the wiring to the Hive from the EP2002.
Didn't think of using a multi meter for investigating the potential wires seen at the thermostat back to the EP2002. Will also try that.

 

[ian1182]

Thanks for the reply much appreciated.
Appreciate the confirmation on the wiring to the Hive from the EP2002.
Didn't think of using a multi meter for investigating the potential wires seen at the thermostat back to the EP2002. Will also try that.

i have updated my post. I suspect it's the brown from EP #4 (or Hive #4) that goes to the thermostat as per the earlier reply from johnmdc. But you should check carefully before making any changes. Hence the recommendation initially to "just turn the stat to max" as that's not touching any wiring. Once you know it works, then move onto the next stage of bypassing the room stat.

 

[ChrisGG]

i have updated my post. I suspect it's the brown from EP #4 (or Hive #4) that goes to the thermostat as per the earlier reply from johnmdc. But you should check carefully before making any changes. Hence the recommendation initially to "just turn the stat to max" as that's not touching any wiring. Once you know it works, then move onto the next stage of bypassing the room stat.

Appreciate the additional thoughts . Thanks again

 

[ChrisGG]

I think that it is the brown wire in 4 at the ep2002 and the earth wire (which has been used as a switched live) in C.

So disconnect both of these and put the grey wire that is also in C to 4 on the Hive.

I thought I'd do a test of the above solution in the existing EP2002. Disconnected the earth wire (used as a switched live) in C and the brown wire in 4. I moved the grey wire from C to 4 in the EP2002. I then used the manual control on the EP2002 to switch the CH on and off. It works! The existing thermostat is isolated and has no function on the CH. HW function also not impacted. All good.

Now I know it works it is a hassle free transfer of the same wiring to the Hive receiver. Thanks once again Johnmdc much appreciated

 

[ChrisGG]

I thought I'd do a test of the above solution in the existing EP2002. Disconnected the earth wire (used as a switched live) in C and the brown wire in 4. I moved the grey wire from C to 4 in the EP2002. I then used the manual control on the EP2002 to switch the CH on and off. It works! The existing thermostat is isolated and has no function on the CH. HW function also not impacted. All good.

Now I know it works it is a hassle free transfer of the same wiring to the Hive receiver. Thanks once again Johnmdc much appreciated

Transferred the wiring from the EP2002 as above to the Hive receiver backplate. Hive all set up and working for the past few days no problems

 

[ChrisGG]

Hi guys, I've got a problem with the Hive now. It's been working fine for two weeks no problems until yesterday.

Basically the CH is running on regardless of the target temperature set on the thermostat. However the CH green light on the receiver is off with no error lights main status light green. Also CH in the app and on the thermostat is off but the heating is running on. Switching the CH on and off at the receiver, thermostat and app also does nothing it carries on working. The only way to switch the CH off is switching the power off to the receiver / boiler and leaving it for a while. Resetting / rebooting the whole system. Note this has only happened a couple of times yesterday and today. Otherwise it has been working no problem.

I did swap out the Hive thermostat with a Hive mini thermostat last week purely because I preferred the smaller thermostat and use the app. Hive customer service deregistered the the original Hive thermostat from my set up. Confirmed all was working fine with the Hive mini. Could it be a problem with the Hive mini? Or a failure of the receiver? Or my wiring!? Note I did do a factory reset of the hive mini yesterday but the same issue has happened today.

The only other thing to mention is that the issue seems to have coincided with the HW button being pressed on the receiver leading bizarrely to the CH running on. Note HW water button is green and lit but CH is off on the receiver. Again HW and CH have been functioning independently with no problems up until now.

Anyway any ideas appreciated!

Cheers

Chris

 

[Mister Banks]

Is this just the normal 3 minute boiler/pump running to cool the boiler down?

 

[ChrisGG]

Is this just the normal 3 minute boiler/pump running to cool the boiler down?

Thanks for the response. No you can hear the boiler gas jets are active and heating. I came home this afternoon and the thermostat had hit 24 degrees with a target set of 18.5. The missus and the kids said they thought it was hot!

Note as above this coincided with my son turning on the HW boost at the receiver. The same thing happened yesterday. When I came home HW light was on at the receiver (my son confirmed he had turned it on). Again the heating was also running but no CH light on at the receiver. Could be a coincidence.

Could it be a boiler fault? Or the CH valve not closing? My understanding is If the central heating light on the receiver is not lit then Hive is sending no commands to the boiler.

 

[ian1182]

Very strange. Since fitting the Hive had you tried a HW boost previously or is it just in the past couple of days?

There are only 3 active combinations the Hive Hub should create. The "inactive" one is HW & CH both off

All I can suggest is to try each of
HW only
CH only
HW+CH

and see if any cause your problem. Allow sufficient time between each for the pump overrrun to end, assuming of course the boiler actually stops when the HW or CH is turned off

There should be no electrical difference between a normal "scheduled" on period and that invoked by a "boost" for either of HW or CH.

Note the programmer does not directly fire up the boiler but rather a zone valve opening activates a switch which then starts the boiler. If you have the chance it's good to review the JW videos on central heating wiring as that explains how it all hangs together.

It is possible that the problem is with a zone valve rather than the Hive itself.

It sounds like the HW boost was still active as you said

"When I came home HW light was on at the receiver (my son confirmed he had turned it on). Again the heating was also running but no CH light on at the receiver."

 

[ChrisGG]

Very strange. Since fitting the Hive had you tried a HW boost previously or is it just in the past couple of days?

There are only 3 active combinations the Hive Hub should create. The "inactive" one is HW & CH both off

All I can suggest is to try each of
HW only
CH only
HW+CH

and see if any cause your problem. Allow sufficient time between each for the pump overrrun to end, assuming of course the boiler actually stops when the HW or CH is turned off

There should be no electrical difference between a normal "scheduled" on period and that invoked by a "boost" for either of HW or CH.

Note the programmer does not directly fire up the boiler but rather a zone valve opening activates a switch which then starts the boiler. If you have the chance it's good to review the JW videos on central heating wiring as that explains how it all hangs together.

It is possible that the problem is with the HW zone valve rather than the Hive itself.

Thanks for the response and noted.

Yes the HW boost function has been used several times without the heating also coming on. It has all been working fine until yesterday. Each of all the active combinations you mention above all working.

I'm now thinking it must be an issue with CH valve not closing perhaps. The Hive seems to be working the boiler / valves more frequently than the old thermostat did. In that the Hive turns the heating on and off more frequently for shorter bursts than the old thermostat. The valves / pumps and boiler were installed in 2009 so getting on a bit!

 

[ian1182]

Thanks for the response and noted.

Yes the HW boost function has been used several times without the heating also coming on. It has all been working fine until yesterday. Each of all the active combinations you mention above all working.

I'm now thinking it must be an issue with CH valve not closing perhaps. The Hive seems to be working the boiler / valves more frequently than the old thermostat did. In that the Hive turns the heating on and off more frequently for shorter bursts than the old thermostat. The valves / pumps and boiler were installed in 2009 so getting on a bit!

I was going to add, with each of the combinbations can you see which zone valve is open and perhaps if you can feel a flow through the pipe.

Does the boiler stop when the HW boost ends?

If the CH zone valve is faulty I would expet the problem to occur during central heating only cycles as well.

If you look at the JW video I linked, around 11:40 in he explains the CH function. As you will see there is no direct link between the programmer and boiler. The programmer activates the zone valve, that closes a switch which starts the boiler. So if the microswitch "sticks" closed the CH circuit will run independent of the programmer.

And yes, the likes of Hive & Wiser run the system more frequently. Traditional systems with mechanical thermostats had a fairly wide hysteresis which just means there was a large margin between the off and coming back on. For example if the stat was set at 20C, it would turn off at 21C and not turn back on until 19C or something like that due to the design of the stat. An electronic stat has no moving parts and hence the Hub can run to a much tigher tolerance. On my Wiser system it's around +/- 0.3 C. It did worry me initially as I was used to a boiler that worked in long on/off cycles and the boiler now performs up to 6 complete on/off cycles per hour. Often the boiler may only run for a couple of minutes as the system attempts to maintain a steady temp.