Hive Heating upgrade help - Danfoss 103

2 Jul 2018
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United Kingdom
Hi there,

I’m looking to upgrade our heating to a Hive smart thermostat. Currently we have gravity fed hot water and pumped heating. All controlled by a Danfoss 103 timer and a Honeywell thermostat.

The issue I’m having is figuring out how to re wire the Hive... please see attached photos and diagrams...

If anyone can help out with this puzzle that would be great!

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The Danfoss 103 is a single channel timeswitch, so it operates the heating and hot water to the same on / off periods. The existing method of wiring will not work with Hive. With the Hive, the room thermostat is incorporated as part of the time control, which would mean you would only be able to heat hot water when the radiators were hot too. So, in the middle of a heatwave as we are now and the radiators are not heating up, the hot water would never heat up either. Therefore you cannot use the existing wiring arrangement as it is, it will need to be changed.

You require the Dual channel version of the Hive to allow you to heat the hot water without the radiators getting hot also. It would be wired as below. [The single channel Hive is for systems without a hot water cylinder, such as combi boilers]

Gravity HW Hive.jpg

Whilst the Hive will work in a fashion with your antiquated plumbing system, it will not provide thermostatic control of the hot water, or allow the central heating to be 'on' independently (the hot water will also need to be 'on') To do it properly you would need to convert it to a 'Y-Plan' system with a three port motorised valve, but it becomes a much bigger job. However Hive do make provision for an arrangement such as yours, but you will need to switch it to 'Gravity-fed' mode as follows:

Hi stem
Thanks so much for your response. Really helpful!

Yes I’m aware that our current system is pretty antiquated and that we won’t get the fully functionality by upgrading to Hive (ie having to use it in gravity fed mode etc. )

However I’m still keen to set up the Hive as it would add some more functionality than we have currently for relatively low cost (ie not overhauling the whole system to a Combi or y plan).

Thank you for the wiring diagram. It’s very helpful. How do I go about re wiring what I currently have to what is on the diagram you have shared?
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Unfortunately it's difficult to see enough detail from the photos to be 100% certain, so you should check carefully that my assumptions are correct and that the cables actually go where I think they do. If in any doubt don't proceed and post back.

1) The 230V mains supply cable should be fairly straightforward to locate. It should come from a 3A fused spur and connect to the Danfoss 103 terminals 5(N) & 6(L). It will probably be the cable with the red and black wires in terminals 5 & 6, but please check to be sure. This 230V supply will go to the Hive N & L. So, no surprises there.

2) Identify the three core cable that currently goes to the existing Honeywell room thermostat. That will need to be removed completely as it will no longer be used. It should presently be connected to the Danfoss terminals 1 (red), 2 (yellow), and 5 (Blue). If you have anything different, post back.

3) Then there should be two cables left. One cable will go to the pump, (connected to Danfoss terminals 2 and 5) and the other cable to the boiler (connected to Danfoss terminals 1 and 5) These cables would be removed and reconnected to the Hive as per my diagram. The wires presently in terminal 5 are the neutrals. [Some, but not all boilers also require a permanent live, but I don't see this in any of your photos]

4) Don't forget to reconnect all of the earth wires. Whilst the Hive itself doesn't need an earth connection the pump and boiler do. So use the Hive 'earth tether' to connect them to the supply earth.

I mentioned the limitations of your system because some think that by fitting a Hive / Nest etc., to their old system that it will provide the full functionality and are disappointed to find that the limitations they had before are still there.
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