Potterton EP2002 to Hive Active heating and hot water help!

[chunkybuns]

Yeah, I set it to gravity fed as the system is gravity fed.
I’ll try it on fully pumped and see if that changes it. Daft thing is it shows heating and hot water independently on the screen but the receiver always has both lights on when the system is running.

 

[stem]

By the term "gravity fed" the Nest instructions are not referring to there being a cold water feed and expansion tank in the loft. You can still have a fully pumped system with this type of installation

Gravity fed is referring to very old heating systems where the hot water cylinder is heated by gravity circulation of hot water from the boiler (it isn't pumped) without any other control devices (eg a motorised valve). With this type of system it isn't possible to have the central heating 'on' without the hot water being 'on' at the same time also, because of the limitations of the plumbing.

However from your photos I see you have a 3 port motorised valve, so gravity fed is the wrong option for your system.

I assume that you took the thermostat photo before you linked the live wires.

 

[chunkybuns]

Ahhh. I see.
Yes, those are the before pictures.

 

[chunkybuns]

Ok. Been at this for hours tonight trying to figure out why it’s still not working properly.
Managed to get the controller back out of gravity mode and it’s turning on and off ok.
When I choose heating only. Pump runs but the heating motorised valve doesn’t open unless I select hot water. Then it opens and we’re all roasty toasty.
If I select hot water only. Nada. Nothing, nowt. The controller selects hot water but no pump and no sign of the hot water valve shifting. I downloaded an s type wiring diagram today but it doesn’t appear to be a very good match.
I do have some additional strange accoutrements to my system in the form of stats on the pipework down in the garage on the boiler pipes.
Gonna have another bash tomorrow night.

 

[chunkybuns]

Sorry. I meant the heating valve

 

[stem]

Did everything work OK before you installed the Hive? If so, then it will be something you have done wrong when transferring the wires over from the EP to the Hive. If you start altering things that you haven't touched in the process already, you can run the risk of introducing more problems.

The EP contained two internal switches. On/off for hot water and on/off for central heating. The Hive is exactly the same, it contains the same two switches, so electrically speaking nothing should have changed (except for the bypassing of the old room thermostat).

The pump is not normally connected to the programmer. Usually it is controlled either from the motorised valve, or the boiler depending on the set up you have.

If the pump is wired to the motorised valve/s, then in operation, the motorised valve winds opens the central heating outlet which also triggers an internal switch that is responsible for starting the boiler and pump. However, your valve isn't opening but the pump is running, suggests to me that it's possible that the pump wiring was connected to the EP spare terminals and now somehow you have connected it to the heating on connection at the Hive, and maybe the motorised valve is now connected to where the pump should be. All you can do is trace the wires back and check, it's not possible to be more specific over a forum without being physically present to inspect the wiring.

The Hive 'heating on' terminal (4) normally would go (via the now joined original thermostat wires) to the motorised valve's heating live wire (white wire if it's a 3 port valve / brown wire if it's a 2 port valve). That of course doesn't take into account the "strange accoutrements" which will be connected in somewhere.

 

[chunkybuns]

Lol, yeah, and also not helped by the (I’m going to assume)installer using a bit of 2.5 flex to connect up the heating valve utilising the green/yellow where a white would be.
I’m gradually working my way through it and agree, i think the issue is the wiring at the controller.

The connections were

N - 2 neutrals
L - 2 Reds (one live bridged from 5)
1 - not used
2 - not used
3 - red
4 - yellow
5 - live and bridge to L

Now... I’m wondering if the red in L and the red in 5 were back to front. ???

 

[stem]

It's easy done. Done it myself in the past. I now have a supply of different coloured cable ties, that I sometimes use to identify wires where there are several of the same colour before I disconnect them.

Unfortunately I can't help you with the colours of the wires used. They are chosen by the original installer and based on his personal preferences, and the cables they had to hand. It's what's connected to each end of the wire that matters, not the colour of the insulation.

Not sure what you mean by:

Now... I’m wondering if the red in L and the red in 5 were back to front. ???

They were both connected to the L anyway, so wouldn't have made any difference, and the link to 5 should have gone now. The Hive has this connection made internally.

Once the link between EP L and 5 has been discarded, if there were any other remaining wires in EP 5, they should now go to the Hive L.

 

[chunkybuns]

Yeah, I'm thinking that's where I went wrong. I left the remaining wire in 5.

That would mean the heating on was in the hot water on connection and the hot water on was in the heating off connection.

When I get home I'll move the red from 5 to L and shuffle the other two up one. Hopefully that'll sort it.

 

[stem]

Yeah, I'm thinking that's where I went wrong. I left the remaining wire in 5.

I don't know how you managed that. The Hive doesn't even have a terminal 5!

Be careful though, trial and error movement of wires without knowing what they do and where they go, can end up causing damage.

 

[chunkybuns]

No, I meant the live was in 4, yellow in 3 and hot water in 2

 

[chunkybuns]

OK after industriously working my way through the various connections I have now established the following:

The heating motorised valve powers open but the NC/NO connections remain open circuit whichever position its in.
The hot water motorised valve doesn't power up and is permanently open and the NC?NO connections are permanently closed whichever position its in.

1 - Live 3 x Red
2 - Empty
3 - Live 1 x Red ( Still to identify)
4 - SwL to boiler 1 x Yellow
5 - Hot water Live from Controller 2 x Red
6 - (Think its the cylinder stat still to trace out) 1 x Yellow, 1 x Blue (was connected to HW valve Live)
7 - Heating Live from Controller and output to room stat 1 x Yellow Live, 1 x Red to stat
8 - Return from room stat 1 x Yellow (Live when stat Bridged)
9 - Pump supply from boiler 1 x Red
10 - 1 x Yellow and 1 x Red(live) Still to identify

Whoever has effected a repair previously had put the Heating valve across 8 (from room stat) and neutral, and used the heating pump contacts as a bridge between 5(Hot water live from controller) and 4 (Switched Live to controller)

This means that when the heating demand is on the hot water is automatically on (because the valve is permanently open), and when heating is off, the power to the heating valve is removed so the water passes through the hot water coil.

I have still to identify which are the Frost stat and Water return frost protection which I'm assuming are to be linked to the heating valve and pump control and the return flow stat to the boiler start.

Slowly getting there and in the meantime I have ordered new heating valve and hot water valves. and then I will re-wire the system back to how it should be. That should then mean the hive will be able to select heat without water and vice versa.

 

[chunkybuns]

All working fine now. Two new valves fitted. Power to HW one from 5. Power to Heating one from 8.
Both Grey switch wires connected to No 3 and Oranges to No 4.
Now it allows HW and Heat to operate independently.