Hive wiring queries

[IJWS15]

Fitted a hive system last week and while the hive is working it isn’t switching the system as expected.

The boiler is a Potterton Kingfisher (about 45 years old) previous controller was a Potterton EP2000 (heating and water switching at the same time). Y plan with 3 way valve.

We get hot water and heating but only if both are on, boiler doesn’t strike up if only HW is on.

We have L, N, HW ON, HW OFF and HEAT ON connected at the hive replicating how the old controller was connected. The room stat is disconnected and a link fitted at the wiring centre.

Diagram showing how the old controller was wired, and feeds into it from Fcu, boiler and wiring centre. I did not replicate the link from L to T5 as there is no T5 on the hive

I don’t fully trust the house wiring as the previous occupant had fitted a second room stat using twin&earth and in doing so left the neutral from the first thermostat loose in the wiring centre (live at times)

Plan for tomorrow is to rewire the wiring centre to a known diagram and see if it works as I can’t see anything wrong at the new hive switch. Tracing feeds is not easy as the boiler is about 40ft and one floor away from the wiring centre .

Am I missing something obvious?

ps I think the neutral from the cable top left is connected to the neutral at the hive baseplate (there definitely three wires connected to neutral but the diagram shows 2 - heating is on so don’t want to take the controller off again to check)

 

[CountryFan]

Was it working the same before you replaced the Potterton? Have you tried hot water only from cold?

 

[ericmark]

With the Y Plan, the DHW only does not power or move the motorised valve,

The red line shows the DHW connection to give us DHW when we have no central heating, if the red line is completely missing, we will still get DHW when the boiler is running to give CH.

The grey wire, into the zone valve, stops the DHW getting too hot, and also allows us to turn DHW off.

So with no DHW wiring at all, you will still get DHW when the central heating is running.

 

[IJWS15]

It worked before we changed it …… But. …….. It was always with heating and hot water at the same time. Single channel clock so couldn’t run them at different times so it may have had the same behaviour before without us noticing as both were generally on. When heating wasn’t wanted we used the immersion heater for hot water (the boiler puts out a lot of waste heat!)

Been thinking, when we did use it just for water we had hot radiators in the bathrooms and some bedrooms. One reason why we used the immersion heater.

With HW only on the boiler doesn’t fire up.

 

[IJWS15]

Was it working the same before you replaced the Potterton? Have you tried hot water only from cold?

Possibly doing what it is doing now - HW and heating generally used at the same time. Hw on only and the boiler doesn’t strike up.

 

[ericmark]

I have worked out, in summer, cheaper to use the immersion heater, at least with my house. In winter, I have no option, but my DHW will stay hot for 3 days, so hard to say what heats the water in winter.

 

[flameport]

But. …….. It was always with heating and hot water at the same time.

Probably been wired wrong for years or even since it was installed.

Plan for tomorrow is to rewire the wiring centre to a known diagram

If someone has been tempering in the past, it's always quicker to just start again with the wiring, rather than attempt to work out what previous incompetents have done.

 

[Taylortwocities]

Looking at the age of the programmer, and probably the system, it smells of an often-met problem with the old hot water system being gravity.
Have a look at this thread
https://www.diynot.com/diy/threads/hive-install-with-gravity-hw.557070/ and particularly post #3 from @stem
it may help.

 

[IJWS15]

Looking at the age of the programmer, and probably the system, it smells of an often-met problem with the old hot water system being gravity.
Have a look at this thread
https://www.diynot.com/diy/threads/hive-install-with-gravity-hw.557070/ and particularly post #3 from @stem
it may help.

Definitely all pumped, there is a three way valve (Plumb Centre branded) so it has been replaced at some point as they weren’t called plumb centre when the house was built. We have had gravity HW in the past and they have larger bore pipe for the HW (which this doesn’t ) and there is a long horizontal run from the boiler to the pump.

The house is plumbed a little oddly as all the cold taps except the kitchen sink were fed from the cold header tank. We have redone the cloakroom and it is now fed from the cold main so we now have two taps with drinking water, bathrooms still to do.

 

[EFLImpudence]

The house is plumbed a little oddly as all the cold taps except the kitchen sink were fed from the cold header tank.

That's quite normal.

 

[IJWS15]

That's quite normal.

We haven’t had one plumbed that way before and have had houses built in the 1860s, 1950s, 1970s and 2000s.

 

[ericmark]

The Y Plan is an odd system, to stop DHW heating it needs power, and often we see where the off wires are missing. With the old boilers, this was not a problem, but the condensing boiler if hot water is returned to the boiler it will reduce output.

I was told for years it was cheaper to use gas or oil to electric, however in this house, the immersion heater controller actually says how much is used. Also, since my boiler does not modulate, can work out how much used by run time. I realised it used about 5 times the energy to heat with the central heating, due I would think from losses from the boiler and pipework, not a problem in winter as heat still goes into the house, but in summer, specially if running an AC to cool the house, so with a standard electric supply they break out about even, neither power source is cheaper. But with solar or off-peak, then electric works out cheaper.

As to the new comb-boilers, heating a whole boiler up, to wash hands, can't see how that is a cheap method.

So although clearly better if the DHW works correctly, it is no real problem if it does not.

 

[IJWS15]

​

Jusr rewired the wiring centre in line with diagram above with adjustments due to wiring centre being in the landing cupboard and boiler, supply FCU and controller being in the utility room .

All working fine, boiler fires regardless of whether heat or HW is turned on. Didn’t record what it was originally.

Wiring at controller was correct.