Replace Sunvic Select XL with Hive?

[dnjb]

Hi.

What I have -
A Worchester Greenstar CDi 30 upstairs, and a Sunvic Select XL in the kitchen downstairs - this is the extent of my heating "system", no thermostat or anything. All the radiators have TRVs so I use those as a poor man's zoned heating system.

What I want -
The timer is a pile of crap - so limited and annoying to use - and I would like to replace it with a Hive or something similar (but not Nest). Fundamentally all I want is an easier to use, and more versatile, timer and the ability to manually turn off/on my heating over the interwebs. I suppose, ideally, I would also introduce a thermostat into the equation although it's not really required.

My thoughts (using Hive as a reference) -
From what I gather all I need to do is plug the Hive Hub into my router, replace the Sunvic with a Hive Receiver and stick the Hive controller pretty much anywhere - job done! Is it really that simple, as I've read a lot about things being installed next to the boiler, things not being able to control certain boilers, etc. And the uncertain part for me is - the wiring for the Sunvic as compared to the Hive Receiver?

I like to do things myself when I can, but when it comes to electrics and such, it's very much a "like for like" (like replacing wall sockets with ones with USB chargers, or an old electric hob with an induction hob, for example) as I don't really get the ins and outs. If it really is a case of doing what I described above then awesome, but if not then I'd rather know before I started!

Cheers!

PS. I already have Lightwaverf lighting and a hub but their support is poor and the app so flaky I don't want to go with them for the heating controls, particularly given the poor reviews they have on Amazon.

 

[dnjb]

The wiring behind the Sunvic...

 

[stem]

First of all the Hive is a programmer / timer, and a thermostat all combined into one unit, (as is Nest and the others) so you will be "introducing a thermostat into the equation"

It is also now part of the building regulations that new systems have a boiler interlock to make them energy efficient and shut the boiler down when no more heat is required. [TRV's don't do this, they shut the radiators down but the boiler keeps on going and wasting fuel]

So back to your question.

There are different versions of the Sunvic Select, but looking at the wiring in your photo, it would appear to me that yours is as per the model detailed below. These details will be in the installation instructions for it, or printed on the back of it somewhere for you to check and make sure.



If it is the same as the above, then the Hive Single Channel version will be a straight swap as you can see from the drawing below the connections correspond terminal for terminal.



I'm assuming your Worchester Greenstar CDi 30 is a combi boiler version that provides hot water on demand, so doesn't presently have any time control for hot water.

When you install the new thermostat, there should be at least one radiator in the room where the new thermostat is fitted that doesn't have a TRV fitted to it. Otherwise it could interfere with the operation of the new thermostat and stop it working properly.

 

[dnjb]

Thanks for the quick reply!

That first diagram is indeed on the back of the timer (it's a 107XL, now I see the label on the back) although it says fused 6a, rather than 3.

The Greenstar CDi 30 is a combi so no need for water, no.

Okay, kind of understood with the thermostat/TRV situation... I'm wondering how best to situate that given my setup. My place is a pretty chilly old cottage and I live alone (except on occasions the girlfriend is here and the heating has to go up everywhere! ) so only really fully heat rooms as needed - office TRV on 5 during the day, all others on 1. At night I turn the office TRV down to 1 and the living room up to 2 or 3 (doesn't need more as it's the only properly insulated room.)

I guess I should put the thermostat in the coldest room (hallway) in the house so it would only go off if that place hit the target and keep using the other TRVs as normal? Does that make sense or is my logic backwards?

 

[75pete]

Looking at your picture, is that a universal backplate? If so, where can I buy a new one?
Thanks
Pete

 

[stem]

They are supposed to be universal but can be a bit tight occasionally. The Hive will come with one.

 

[wwwebber]

Thanks for the quick reply!

That first diagram is indeed on the back of the timer (it's a 107XL, now I see the label on the back) although it says fused 6a, rather than 3.

The Greenstar CDi 30 is a combi so no need for water, no.

Okay, kind of understood with the thermostat/TRV situation... I'm wondering how best to situate that given my setup. My place is a pretty chilly old cottage and I live alone (except on occasions the girlfriend is here and the heating has to go up everywhere! ) so only really fully heat rooms as needed - office TRV on 5 during the day, all others on 1. At night I turn the office TRV down to 1 and the living room up to 2 or 3 (doesn't need more as it's the only properly insulated room.)

I guess I should put the thermostat in the coldest room (hallway) in the house so it would only go off if that place hit the target and keep using the other TRVs as normal? Does that make sense or is my logic backwards?

Generally you should put the stat in the room that you occupy most to ensure it hits the temp that you want and then you adjust other TRVs accordingly. However, if you have cold spots that you want to address then yes put it in the coldest area but ONLY if the area is capable of reaching the target temp AND the rads or set to be FULL on otherwise your boiler will be thrashing away getting no where fast.

 

[stem]

it says fused 6a, rather than 3.

That is the rating of the programmer. the Fused connection unit supplying it and your boiler will have a 3A fuse in it. (Good luck finding a 6A fuse in the UK) The thermostat should be in the last place to warm up. Otherwise it will turn off the entire heating system leaving other rooms cold, so they have to heat up first and the TRVs will stop them overheating.

 

[dnjb]

They are supposed to be universal but can be a bit tight occasionally. The Hive will come with one.

Indeed - I discovered this. The bottom screws on the existing plate weren't long enough to accommodate the Hive's plastics, even with a bit of force. So I ended up fitting the Hive backplate rather than shaving a bit of the Hive Receiver.

Generally you should put the stat in the room that you occupy most to ensure it hits the temp that you want and then you adjust other TRVs accordingly. However, if you have cold spots that you want to address then yes put it in the coldest area but ONLY if the area is capable of reaching the target temp AND the rads or set to be FULL on otherwise your boiler will be thrashing away getting no where fast.

Yeah, this is the tricky part I guess - the room I occupy the most during the day (office) NEVER gets up to temp this time of year - it has a wood burner but I usually just use a portable gas stove to bump things every couple of hours or so. The other room I occupy a lot (living room) EASILY gets up to temp. So basically I kinda have to have the heating on permanently while I'm in the house and use the TRVs to keep the living room from becoming scorchio. So the thermostat is sort of wasted - I suppose it will be useful for frost protection as I used to just turn the heating completely off whenever I went anywhere, but aside from that I can't think of a truly useful place/purpose for it.

Edit: Oh - as for Hive, it's pretty good for the £109 I paid for it, but wouldn't have paid much more. Couple of annoyances, which I can live with, and which I could have discovered with more research, but coulndn't be bothered to for the price! No Advance button/function on the actual thermostat. Weird! Easily remedied as they have a widget for Android that is a one button press to advance, so no need to go into the app fully. Would have been nice on the 'stat - there is even a "spare" button for the heating only kit as it still has a Hot Water Boost physical button - I'd be happy to map that to Advance if I could.