Honeywell ST699 to Hive issues

[monkeyalan]

Good evening,

I have lurked in these forums for many years and been grateful for the hints and tips seen in the threads. I have searched these forums for people who had similar issues and can see that moving from the Honeywell ST699 to Hive can cause problems.

I had a sparky install the Hive but he is now stuck too. I have attached photos of our set up, whilst the Oil boiler is old it has been regularly serviced and until the Hive switch was working well.

With the Honeywell we could toggle the heating or hot water and the boiler would fire up instantly - this was the same when using the timer.

Hive installed and now the water or heating wont come on when toggled either via the thermostat or the receiver on the wall.
If I move the temp gauge in the boiler it does come on for a while then turns off.

I will obviously need to find a tradesman who knows what he is doing but any help would be much appreciated so I can point them in the right direction.

Thank you!

 

[CountryFan]

Wow that cylinder thermostat is high - I would lower it to at least 60. Regards the hot water and heating - hot water could be satisfied and with the weather as it is, maybe the thermostat for the heating is satisfied too?

Can you post a photo of the Hive calling answer actual temperature please?

 

[Mister Banks]

Could be wired incorrectly, can you post a photo of the Hive wiring and did you take a photo of the Honeywell wiring before you removed it.

 

[CountryFan]

did you take a photo of the Honeywell wiring before you removed it.

It’s was done by an electrician

 

[Mister Banks]

It’s was done by an electrician

Ok, so did the electrician take a photo before they removed it?

 

[ericmark]

Step one is to work out what system is being used, I see no motorised valve, so would think likely C Plan. The tank thermostat basic only works in the summer, and allows you to leave the boiler turned on, and will fire the boiler when the tank cools.

The standard Hive wiring diagram was not really designed to have the tank thermostat, what is causing the problem is the combining of programming and thermostat into one device.

Hive is an unusual thermostat in the way it works with C Plan. It has two sets of contacts, one runs the boiler, the other runs the pump, and the idea is if only DHW is required, only boiler runs, and if both DHW and CH is required, both pump and boiler runs.

So one would need some relays to use the tank thermostat in the summer, but I have found cheaper to use an immersion heater in the summer, so the question is do you need the tank thermostat?

The boiler I found needs to run 4 times a week at ½ hour each time, which works out at around the 25 kWh mark, my immersion heater runs through an iboost+ so it shows how much used, and typical is 2.5 kWh per week, the rest is used to heat the boiler and pipework. So oil would need to be 10% of the price of electric to be worth using, it is cheaper than electric but not that cheap.

So is it C Plan? Have you no motorised valves?

If the pump supply worked a relay to run the boiler, then it could be made to work. But can't really see the point, simply use electric.

 

[monkeyalan]

Ok, so did the electrician take a photo before they removed it?

I have asked this!

 

[monkeyalan]

Wow that cylinder thermostat is high - I would lower it to at least 60. Regards the hot water and heating - hot water could be satisfied and with the weather as it is, maybe the thermostat for the heating is satisfied too?

Can you post a photo of the Hive calling answer actual temperature please?

Sorry what do you mean by a photo of the Hive calling answer?

 

[CountryFan]

Sorry what do you mean by a photo of the Hive calling answer?

The Hive’s actual temperature calling heat. I think autocorrect changed something.

 

[ericmark]

My thought was, why would an electrician have a problem? And it would seem likely with a C Plan with a tank thermostat, he could get caught out. The C Plan was improved over the years, but only the first one was supported by the Hive system. Same with Nest, no one has really sat back and worked out how to use with the tank thermostat, which only does anything in the summer anyway.

But the question is one, have you got a motorised valve? And two, is it worth the hassle to work out a summer only option when you have an immersion heater?

I was told with my boiler, it is better for the boiler that it can cool by heating the DHW, so winter still use boiler, the immersion heater thermostat is set lower to CH so if central heating running, the immersion will not work.

But need to know what you have, and your thoughts about only using immersion in the summer?

 

[monkeyalan]

Not against using the immersion over the summer. We have electric showers so that’s not an issue.

Is there another system other than Hive which would work in this situation?

 

[ericmark]

All it needs is a relay, so when the pump runs, it also runs the boiler. But really can't see the point. In summer, cheaper to use an immersion heater. This is down to the energy used to heat the boiler, before any hot water comes out, a boiler needs around 1.5 hours burn time to work efficiently, and with my DHW it needed 20 minutes.

 

[monkeyalan]

My thought was, why would an electrician have a problem? And it would seem likely with a C Plan with a tank thermostat, he could get caught out. The C Plan was improved over the years, View attachment 380699View attachment 380700View attachment 380701 but only the first one was supported by the Hive system. Same with Nest, no one has really sat back and worked out how to use with the tank thermostat, which only does anything in the summer anyway.

But the question is one, have you got a motorised valve? And two, is it worth the hassle to work out a summer only option when you have an immersion heater?

I was told with my boiler, it is better for the boiler that it can cool by heating the DHW, so winter still use boiler, the immersion heater thermostat is set lower to CH so if central heating running, the immersion will not work.

But need to know what you have, and your thoughts about only using immersion in the summer?

I can’t work out how the old system using the ST699 allowed the independent use of the water and heating system which it did.

 

[ericmark]

I can’t work out how the old system using the ST699 allowed the independent use of the water and heating system which it did.

To do that, somewhere somehow there is a motorised valve. You can't turn the DHW off (and leave CH running) without a motorised valve.

 

[monkeyalan]

Is this the valve I am looking for? To me this suggests the Hive installation is just a standard Y set up? Thanks for your ongoing help with this.