Hive installation- CH OFF wiring missing - Gravity Fed Y plan

[Adam_K]

Hi everyone, new guy over here. I'm ok with electrical DIY, but plumbing (and central heating system) is not my strong side, so sorry in advance if I write something stupid.

Now to the issue.
I wanted to make my home a bit smarter, so I bought Hive Active Heating - Smart Hive Thermostat & Heating Control.

I have gravity fed system and as far as I can tell from valve and pipework I have Y Plan (photo attached).

There is a control panel next to my boiler, but it's missing CH OFF wiring that Hive asks for.

Also, not sure is it important, but hot water tank can be heated by electricity as well.

There is also a wired thermostat in hall with 3 wires connected to it.

I'm not sure what to do about missing CH OFF as well as what to do with old thermostat wiring.

Any help would be appreciated.

Thanks

 

[ianmcd]

The term gravity is what is confusing you, you have an open vented fully pumped Y plan system, gravity HW is a completely different animal, follow the wiring for a Y plan not gravity, you do not need a wire in CH off

 

[stem]

From you photo, the Danfoss connections are:

And the Hive Dual Channel's are:

The wires move from the terminals of the Danfoss to the terminals of the Hive that have the same function. Ignore the Danfoss 'com' wires, as the Hive has these already made internally for you.

Then any existing room thermostat can either be left set to maximum / permanently on, to prevent it interfering with the Hive, or removed and the connections where the thermostat live switching wires came from linked together.

 

[Adam_K]

The term gravity is what is confusing you, you have an open vented fully pumped Y plan system, gravity HW is a completely different animal, follow the wiring for a Y plan not gravity, you do not need a wire in CH off

Obviously you have way more experience than me, but I might have skipped a few information that might help/ clarify.

I'm 99% sure I have gravity fed system. I have water tank in the attic, that goes to to immersion water tank that's located on the first floor in the airing cupboard. From there hot water is send to bathroom and kitchen. Immersion tank is heated by default from boiler (as far as I know). The pressure on hot water it rather weak.

I have System boiler, not a combi. Baxi Megaflo 18 18kW System Boiler ERP to be exact.

It seams that CH OFF still appears on both diagrams for connecting Hive, and I don't have it where Danfoss timer/control panel was.

From you photo, the Danfoss connections are:

View attachment 155387

And the Hive Dual Channel's are:

View attachment 155388

The wires move from the terminals of the Danfoss to the terminals of the Hive that have the same function. Ignore the Danfoss 'com' wires, as the Hive has these already made internally for you.

Then any existing room thermostat can either be left set to maximum / permanently on, to prevent it interfering with the Hive, or removed and the connections where the thermostat live switching wires came from linked together.

Danfoss didn't have CH OFF, so should I leave it empty in Hive as well? Will it not affect functionality of HIVE.

There are 3 cables attached to thermostat. Brown, black and grey (photo in the first post). Any idea how they should be linked, so I can remover old thermostat? It's rather ugly and it wouldn't have any function anymore.
Also I'm not sure where the cable from old thermostat actually go.


Thanks for the feedback so far peeps!

 

[ianmcd]

some people will not be told, you have a Y plan fully pumped system, a gravity system uses 28mm pipes or larger between the boiler and the HW Cylinder and does not have a pump or any valve on this pipe the boiler heats the water and it rises through Gravity hence the name when it reaches the coil in the cylinder this heat transfers to the HW that comes out of your taps and the hot rising water pushes the cooler water back to the boiler to be heated again, you do not have this , you have a Y plan system fully pumped , you do not need a CH off wire

 

[stem]

The wires move from the terminals of the Danfoss to the terminals of the Hive that have the same function.

The existing wires are moved, and your existing system dictates what they are. I didn't say anything about adding any new wires. If there isn't a wire in CH off now you won't need a wire in CH off with the HIVE. Electrically speaking the Danfoss and the HIVE are both just 'on & off' switches that are simply exchanged like for like.

ianmcd is right. The term 'Gravity' has nothing to do with how the water gets into the system (ie from a tank in the attic) it refers to systems where the hot water cylinder is heated by the natural "gravity" circulation of water in the pipes from the boiler, in that hot water rises and cooled water sinks. With your system this circulation is not by gravity, it is pumped.

There are 3 cables attached to thermostat. Brown, black and grey (photo in the first post). Any idea how they should be linked, so I can remover old thermostat?

If you tell us the make and model of the thermostat that would help. Wiring colours don't as they would have been at the preference of the original installer. One installer may use a black cable for a certain purpose another may use black or grey for the same purpose.

 

[Adam_K]

Thank you guys for clarifying this for me. Saved my some trouble in future as I was planing to set Hive to gravity fed mode. Now I will leave at default 'fully pumped' mode.

The existing wires are moved, and your existing system dictates what they are. I didn't say anything about adding any new wires. If there isn't a wire in CH off now you won't need a wire in CH off with the HIVE. Electrically speaking the Danfoss and the HIVE are both just 'on & off' switches that are simply exchanged like for like.

However I will remove old thermostat that was responsible for switching CH on and off (when Danfoss was set to Heating ON). Will this not change anything in my setup? I guess not, but I want to double check.

If you tell us the make and model of the thermostat that would help. Wiring colours don't as they would have been at the preference of the original installer. One installer may use a black cable for a certain purpose another may use black or grey for the same purpose.

It's Horstmann HRT3 Room Thermostat.
https://www.uk-plumbing.com/brochure/horstmann/HRT3Guide.pdf
How should I go about wires in the old thermostat?

As you mention stem, I should connect it so they are always 'ON', right? So Hive's wireless thermostat will operate Hive's receiver to switch it on or off.

Sorry for being thick. I just don't understand why HW have ON and OFF wiring in Danfoss and CH has only ON.

Once again thank for sticking with me and explaining this stuff.

 

[ianmcd]

Thank you guys for clarifying this for me. Saved my some trouble in future as I was planing to set Hive to gravity fed mode. Now I will leave at default 'fully pumped' mode.



However I will remove old thermostat that was responsible for switching CH on and off (when Danfoss was set to Heating ON). Will this not change anything in my setup? I guess not, but I want to double check.




It's Horstmann HRT3 Room Thermostat.
https://www.uk-plumbing.com/brochure/horstmann/HRT3Guide.pdf
How should I go about wires in the old thermostat?

As you mention stem, I should connect it so they are always 'ON', right? So Hive's wireless thermostat will operate Hive's receiver to switch it on or off.

Sorry for being thick. I just don't understand why HW have ON and OFF wiring in Danfoss and CH has only ON.

Once again thank for sticking with me and explaining this stuff.

because a Y plan needs the HW off and Cyl stat satisfied to move the valve into the heating only mode that is how the valve works

 

[stem]

Ian is right about the motorised valve, it needs a HW off signal to work, but not a CH off.

To decommission the old Horstmann HRT3 thermostat:

1) Find the origin of the thermostat cable with the brown, grey and black wires in. (ie the opposite end of the cable to the thermostat)
2) Note where the brown and black wires are connected.
3) Disconnect all three of the wires and remove the cable. (including any earth if connected)
4) Insert a wire link between the terminals from which the brown and black wires have just been removed from, so that they are electrically joined together.
5) The old thermostat and the cable to it can now be removed.

 

[Adam_K]

Thanks for the help guys.

I can report back that Hive is up and running. For now I left old thermostat in place.

Any idea where the cable from thermostat should go to?

At the moment it just goes into ceiling of ground floor, so it's hard to follow it. What cable in installation should it be connected to? Between the Danfoss and the boiler or somewhere else?

Thanks!

 

[stem]

Well done.

The thermostat cable is the tricky part. It is unlikely to go to the boiler, usually it goes to a wiring centre or junction box somewhere. Unfortunately, there is no set way to wire it in, and it will depend on the personal preferences of the original installer and the layout of the various electrical heating components in your home.

The white box in the airing cupboard above the water heater switch (aka a wiring centre) would be my first port of call. The white wire from the 3-Port motorised valve will be connected to one of the live wires from the room thermostat somehow, but to be sure, any suspect cable should be electrically tested by someone competent in using a multimeter to make sure it is actually the thermostat wire before making any changes.

Otherwise it's a matter of physically tracing it, but even this needs care to make sure you follow the correct cable, if there are several cables passing though a hole in a joist for example.

 

[Just_Col]

Assuming it's a dual channel, would it look like this?

 

[polesapart]

Quite a jump from new years day 2019 to now.

Please start a new thread.