Hive receiver wiring help - oil combi boiler

[ryannf]

Hi,

I have moved to a house with a oil Combi boiler and a thermostat (Grant) which is on the wall in the kitchen.


Can I replace this with my hive receiver do you know? I'm a joiner to trade so very limited ability with things like this although I replaced my old one but it was like for like (a Drayton for the hive) and not an oil boiler I don't know if it's any different.


Is anyone able to help with the wiring. Obviously earth to earth, N to N, L to L but it's the other I am struggling with, what wire would got to what on the hive receiver (black plate in the pictures attached).


Thanks guys

 

[ericmark]

You say Grant thermostat and then show a picture of a Danfoss Randall unit, from pictures it seems the output from the Danfoss Randall unit is linked to Line so the Hive should replace it so going by picture centre picture diagram assuming it plugs into left picture socket, and right picture socket is Hive then.
Danfoss Randall 4 = Hive 3 hot water on.

But then it gets a bit odd, the original link 4 to 2 would mean you can only get central heating when the hot water is already on, so Danfoss Randall 1 could = Hive 4, heating on, but it may be wired that way because domestic hot water is thermo syphon and not sure how Hive will configure. It may be if Danfoss Randall 1 goes to Hive 4 the pump will run but the boiler will not.

Old programmers often had dip switches and mechanical locks, so same unit could give 16 or 10 programs, the latter was used when DHW was thermo syphon, and often with oil boilers there is no run on to cool it down, it needs the thermo syphon to the hot water cylinder hot coil to allow the boiler to not over heat. Often there was no motorised valve on the CH just a pump, so pump running give central heating no pump running gives DHW only.

This very old C plan is common with oil boilers, because the Hive duel channel thermostat is not volt free, it may need some rewiring to use it, this is why I used Nest, with Nest all relays are volt free so there are far more options.

From what I can see if Danfoss Randall 1 goes to Hive 4 it will do no harm, but boiler may not fire up, so you could try it and see what happens.

 

[stem]

First of all remove the links from the Danfoss (L&5) (2&4) Hive has all of the links made internally, so you can forget these.

You require the Dual Channel version of the Hive

You are then left with:

Black wire in Danfoss N = Hive N
Red wire in Danfoss 1 = Hive Heating on 4
Black wire in Danfoss 4 = Hive Hot Water on 3 (note: although this wire is black it is being used as a live)
Red wire in Danfoss 5 = Hive L

Your system is configured as one where the Heating can't be on without the hot water being on also, so you should set the Hive to Gravity Mode of operation.

 

[stem]

I forgot to mention that because the Hive carries out the functions of a programmer and a room thermostat in one unit, the old wired (Grant) thermostat needs to be decommissioned to prevent it overriding the Hive. It can't simply be disconnected as this would leave the heating wiring 'open circuit' and it will not operate. To start with the system would work if the existing thermostat was left in place and set to its maximum setting, but ideally it should be decommissioned properly. If you need any help with this post a photo of the stat and its wiring.

I see @ericmark beat me to it by 30 seconds, however at least we gave the same advice.

 

[ryannf]

Hi both,

Thanks for all that information that's a massive help and yes you are not correct, the sticker on the front of my unit says grant however after checking online (see attached picture) that's the exact same unit as I have.

And yeah that's exactly right, the heating won't come on unless the hot water switch is on. I take it that means that it would need more work than simply wiring the faceplate up?

I have a very crude drawing attached I have done at work. Is decommissioning the old receiver a big job, in both of your professional opinions should I leave this one to someone who knows what they are doing?

Thanks again guys

Ryan

 

[ericmark]

Stem is far better at it than me, I am only an electrician, so take his advice over mine. Your drawing seems OK and from what Stem says you can configure Hive to work, so turn existing thermostat to max, and wire as you show, it should work.

However to remove old thermostat or alter how it works may need a lot more thought, I was advised not to fit motorised valves on the DHW and mine is reverse to yours, running CH will always heat hot water, but don't need to select hot water for central heating to run.

So have you got a thermostat on your hot water tank, and have you got any motorised valves, the motorised valve has a double job, one it turns off CH water and two it acts as a relay. The C Plan has progressed over the years, so not a single plan but a series as control improved.

I know Hive works with the TRV heads, I think you have to turn temperature low on the wall thermostat and set temperature wanted on the TRV heads so the head is always open when pump is running, but I am using Nest so out of my comfort zone.

 

[stem]

That all looks good to me.

The restriction in the working of the system is not because of the controls. The existing controller and the Hive can provide totally separate control of heating and hot water. However, the existing controls will have been configured the way they have probably because of the limitations of the existing plumbing.

Having said that you said that you have a combi boiler, so what is the time control of hot water for, does it have some internal hot water store?

 

[ericmark]

I had considered when Ryannf called it a combi boiler he was using the term incorrectly, I have in old house two boilers one for central heating and one for domestic hot water they were both from same boiler (i.e. combined) but it was split so we could get rid of the hot water tank, we consider with a combi boiler the water tank is within the boiler if there is one, and the domestic hot water is instant, but that is because of conversion, I suppose any boiler which does both functions using simple English rather than conversion is a combi boiler, just not as we know it.

When the boiler was fitted to my old house it was never called a system boiler, that term only arrived as the boiler which combined both my boilers came on the market, and he says can't get central heating without having hot water so I would assume we would call it a system boiler?

I was surprised when I moved to oil fired, it seems not many combi boilers are oil fired, and not many oil fired boilers and condensate type or can modulate to any great degree.

I have three C Plans one already shown, the next uses the normally closed contact of the tank thermostat, and next uses a motorised valve, not going to show how modified for my system, but just pointing out it changed through the years so depends on how old the installation is as to how wired, and that is if actually using a C plan.

So as Ryannf shows we are both saying it will work, assuming original thermostat turned to max. However to remove wiring to original thermostat we need to know more, are there motorised valves, or tank thermostats, and is there two or more pipes to motorised valve, pictures always good.

I am guessing very like my own set up. With no control other than time for domestic hot water? i.e. as original wiring diagram.

 

[ryannf]

Hi guys,

Thanks for all the valued input, what I can do is take a picture of the boiler (it's situated outside) I have never came across one before to be honest so it's all a learning curve for me.

Will pop it in today.

Thanks again
Ryan

 

[stem]

My experience with oil is fairly limited, and oil combi's not at all. Gas combi boilers heat the water instantaneously when a hot tap is opened, so there is no need for time control. Heat only boilers that have a stored hot water in a hot water cylinder do have time control as it needs to be heated up in advance of use.

With regard to the wiring, it doesn't change anything, as the Hive will simply replicate what you already have. It was just my personal curiosity as to what the timed hot water function was actually doing.

 

[ryannf]

Morning guys,

Finally managed to get a crack at the thermostat yesterday and thanks for all your advice, it's working great on gravity mode and saved so much hassle and money getting someone in to do it, was a simple swap over and exactly as you said with regards to wiring.

Thanks again

Ryan

 

[stem]

Thanks for the update, it's good to have your feedback and it helps anyone else that finds this thread whilst looking for help with the same thing.

To satisfy my personal curiosity with regard to...

You said that you have a combi boiler, so what is the time control of hot water for, does it have some internal hot water store?

...did you find anything out?