Heating Stat doesn’t fire boiler.

[HeatingChris]

Hi Guys & Girls!

After a brief search I didn’t find a solution. I’m not clear if I need a Central Heating person, and Electrician or if this is a 30 second DIY job.

I’ve had HIVE for about 6 years and it’s always annoyed me that as per the title, if I want the heating on, I also have to switch on the hot water. In previous houses, the room stat dropping below the threshold could trigger the boiler to do its thing but not in this house.

Switching on hot water makes the Blue device fire (marked hot water pump) and the boiler fires.

Switching on heating makes the red grundfos device fire and pumps hot water from the cylinder around the radiators until the water is cold but never fires the boiler. Is it possible to make this happen? I can’t spot how to wire it so that hot water doesn’t fire the heating too. It should just be the other way.

When the hive installer came he chopped the wires behind the room stat, and these are not connected in the wiring centre at al.

I have attached some pictures and a diagram of what I can identify.

Any tips gratefully received!

Cheers

 

[CBW]

Either a heating engineer or an electrician who understands how zone valves and thermostats work. Seems to me like you might have a 3 port valve? It is the room thermostat that sends a live to the 3 port and triggers the boiler.

 

[HeatingChris]

Ahhh I see. I’ve no idea what kind of valve I have or where it sits. It’s not accessible with the rest of the equipment anyway.

I was hoping it was a case of just bridging a couple of the connections, or switching something around

thanks for the reply.

 

[HeatingChris]

If anyone could shed any light on the likely I identified connections marked ?? in the diagram that would be awesome

thanks

 

[CBW]

It should be where the pumps, wiring centre cylinder are located. Looks something like this:

 

[HeatingChris]

Hmm nothing obvious. It’s not a huge trap door into the floor of the airing cupboard but a sweep of my phone camera reveals nowt. Thanks though.

 

[stem]

You might not have motorised valves if you have separate pumps, one for heating and one for hot water.

Motorised valves contain a microswitch that operates the boiler so when the heating is 'on' and the associated valve opens, the microswitch starts the boiler. Pumps don't have this switch facility, so sometimes the boiler is wired just to the hot water pump, which means the hot water has to be on to operate the boiler, before the heating can be on too. [Other systems have a couple of relays installed to replicate the missing switches and this allows independent control]

If yours is like the first example, the Hive is equipped to deal with such plumbing restrictions and can be set accordingly.

1. Switch off the boiler and receiver
2. Wait at least 5 seconds, switch the boiler and receiver back on
3. Press and hold the hot water button on the Hive receiver for at least 10 seconds

The receiver status light should flash blue for a few seconds. The Hive will now be in an operating mode that whenever the heating is turned on, the hot water will automatically be selected too.

To achieve what you want, I think that there will be some re plumbing, the addition of motorised valve/s and a rewire of the controls to suit, in order to achieve independent control of the hot water and heating.

However it's difficult to tell with the limited information you have given with any certainty, especially without a full plumbing schematic diagram and a complete wiring diagram. There are too many ???? (we can't guess where they go, there could be several possible scenarios, heating systems can be wired up in many ways. I've seen 100's, but can't say any two have been identical) and little specific detail. For example, you show 3 wires going to a cylinder thermostat but no identification of which of the terminals (NO, COM, NC) that each wire is connected to. The wiring diagram also mentions a Range but doesn't show a boiler? and the Hive is missing from the wiring diagram altogether.

Personally I feel that you will need a professional heating engineer to carry out a full survey of the work required. I don't think it can easily be done remotely over a forum.

 

[HeatingChris]

Cheers Guys,

All really helpful insight.

@stem You've put my mind at rest slightly, and made me realise how what i thought was a pretty good effort with diagrams and pics is actually still really lacking!

You're right, i haven't added where the "?" wires even might be heading to! There's a HIVE receiver, and a boiler (Worcester Greenstart - not combi) in the mix somewhere, and probably a mains supply all unidentified but those are all the wires that are connected. The Cylinder Stat only has two wires connected, but presumed the colours indicated their likely intent (if done to spec). The wires which now dont have anything other than themselves is odd (position 3 and 2), but perhaps the old Room stat went there.

I'm going to try the Hive setting you mention tonight - what put me off trying that was that it described itself as the Gravity mode, which i presumed meant a Header tank (which i dont have - see, more useful info )

Good to understand i might not have a mystery valve due to the two pumps. Having Hive set such that when the CH is called for, the HW switches on automatically too is exactly what i'm after so fingers crossed!

If that doesnt work, getting a Pro in will be the next challenge. When i mentioned this to a chap who came to do a boiler service a few years ago he shrugged and said he had no idea :-/

Thanks again all.

 

[stem]

I'm going to try the Hive setting you mention tonight - what put me off trying that was that it described itself as the Gravity mode, which i presumed meant a Header tank (which i dont have - see, more useful info )

Gravity fed and gravity circulation are completely different things. Gravity fed refers to the header tank that fills the system. Gravity circulation refers to the natural circulation of hot water rising as heated and falling as it cools. Your system is further complicated because your hot water isn't actually circulating by gravity, it has a pump to assist it, but it's a different pump to the heating.

All that setting the Hive to 'gravity mode' will change is that when you select the heating to be 'on' it will automatically put the hot water 'on' as well. It doesn't work in reverse, so you will be able to have the hot water 'on' in the summer without the heating.

It is a bit unusual to have a cylinder thermostat in such installations, but there are a few possibilities, it maybe that it could / should be able to have the heating on without the hot water, but some thing has failed. Maybe the cylinder thermostat just controls the hot water pump and the boiler is controlled by the Hive. A pro would soon be able to advise after making an inspection.

 

[HeatingChris]

Gravity fed and gravity circulation are completely different things. Gravity fed refers to the header tank that fills the system. Gravity circulation refers to the natural circulation of hot water rising as heated and falling as it cools. Your system is further complicated because your hot water isn't actually circulating by gravity, it has a pump to assist it, but it's a different pump to the heating.

All that setting the Hive to 'gravity mode' will change is that when you select the heating to be 'on' it will automatically put the hot water 'on' as well. It doesn't work in reverse, so you will be able to have the hot water 'on' in the summer without the heating.

It is a bit unusual to have a cylinder thermostat in such installations, but there are a few possibilities, it maybe that it could / should be able to have the heating on without the hot water, but some thing has failed. Maybe the cylinder thermostat just controls the hot water pump and the boiler is controlled by the Hive. A pro would soon be able to advise after making an inspection.

Every days a school day It sounds like trying the other Hive mode cant do damage, it just might not do as i hope. Thanks again (i'll update just for interest either way when i try it!).

 

[HeatingChris]

Omg that’s only gone and done it!

bloody awesome. Can’t believe I’ve endured the crappy set up for over 5 years because the BG engineer who fitted it told me that’s the only way it would work!

thanks guys!!