Hive CH Automation (again)

Every other email from Screwfix tries to sell me a Nest or Hive system, so I thought I'd have another look at them with my holiday flat in mind.

I currently have an S-Plan system with an unvented HW cylinder. There is an electronic (manual) timer for both HW and CH. The HW circuit has a tank stat which controls the HW 2-port valve. The CH heating valve (both timing and temperature) is controlled by a wireless programmable thermostat (with the CH side of the manual timer being set to permanently on). There are TRVs on most radiators.

The current system provides *most* of what I need, but it doesn't allow the heating to be switched on and off remotely not does it allow the temperature to be monitored remotely. The flat gets pretty cold when unoccupied in the winter months and it would be nice to be able to turn the heating on a few hours before we plan to arrive each time so that it's warm when we get there. In theory we could do this by using the 'holiday' mode on the programmable stat, but that requires us to know when our next visit will be - and we don't always know that.

I'm not interested in a system which is too clever by half by trying to second guess when we're in or out nor in anything with any more zonal granularity than a single heating zone with a few TRVs. On that basis, a Hive 2 system appears to be a pretty good match. Although there's no real need to have remote control of the HW, this is included with most of the Hive 2's on offer, so I may as well use it - and get get rid of all the current timing devices.

I've read past threads on the subject and the Hive 2 Installation Manual, and I have a few queries to which I haven't been able to find answers.

How does it do HW control? There's no mention of a HW temperature sensor so I assume that it is used in conjunction with the existing cylinder stat, and just provides timing. Is that correct? What does HW boost do? I assume that it simply turns the HW circuit on at a time when it would otherwise be off - leaving the cylinder stat to control the temperature. Is that correct?

What does CH boost do?

It appears that the heating can be remotely controlled by SMS messages for the benefit of people who have tradition mobile phones rather than smartphones. How does that work? Is there a SIM card in the unit, or does the SMS message go to a Hive server which then communicates with the unit over the internet? If the former, do you have to pay for a mobile service of some sort?

Some people have expressed concerns about being reliant on an external server - which could be withdrawn at any time. Since Hive is a British Gas system, I doubt that BG will cease to exist any time soon, but have they made any public pronouncements about long-term support for Hive? AIUI, once you have bought the hardware you can access the Hive servers for free without having to pay any subscription charges (unlike trueCall junk call blockers, for example). Is this correct?

Answers to the above questions from those knowledgeable in the subject will be much appreciated.

Reply to
Roger Mills
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I installed a Hive on our boiler and it works great.

Hive consists of three boxes: a controller (simple on/off switches that are connected to the boiler); a wireless thermostat; an internet hub. The three units talk by a private wireless link - private in the sense that they are not part of your internet wifi. The hub connects by Ethernet to your internet router; I don't think it has the option to use wifi instead.

We have a combi boiler which pre-heats a reservoir of hot water and keeps that up to temperature, and then feeds that initially when a hot tap is turned on, to cover the time lag until the boiler can heat the incoming cold feed. Because of this, and the fact that we only want the pre-heat during waking hours, we needed to get a two-channel Hive: one for the hot water which is simply a timer, and one for the CH which sets the desired temperature at different times of day.

If your present time controller allows you to schedule times of hot water as well as CH, you too probably need dual-channel Hive.

The Hive takes the place of the timers for HW and CH and of the CH thermostat.

HW is simple: your controller will have a "HW on" wire which is connected to live when the HW system is on; any thermostatic control of HW temperature will be done by a thermostat in the boiler and/or the hot water cylinder which will remain unchanged (I think).

For CH I think you would replace your current wireless thermostat with the one provided as part of Hive. The CH section of Hive has two wires: "CH on" and "CH off". For simple systems "CH on" goes live when the boiler needs to be turned on. Some systems may also use "CH off" to close any valves after the boiler has been turned off; ours didn't so that wire is unused.

The Hive turns on the CH whenever its wireless thermostat notices that the room temp is below the desired temp. You can define desired temp as a function of time - eg you can set it to 15 degrees between 22:00 and 07:00,

20 degrees between 07:00-09:00 and 18:00-2200, and 18 degrees at all other times.

If you had a wired thermostat, you'd bypass that so it is permanently in the "calling for heat" position (as if room temp was permanently less than desired temp). Your present wireless stat may have a switch which is turned on and off by the wireless stat; if so, connect to be permanently on.

CH is normally wired as two switches in series: timer controller and stat. Hive becomes a single switch that does both time and temperature control.

As well as being able to control the temp by turning the dial on its wireless stat, you can also do the same using either a web page or an Android/iPad app - these allow you to control the temp manually (as if you'd turned the knob on the stat) or to alter the schedule of temperatures. There is a Boost button which keeps the temp at its present setting for an hour longer than the schedule (eg it would keep temp at 20 until 2300 and then 15 from then until 0700, in my example above).

I suggest you get a central heating engineer to look at your system and make sure that Hive's settings (HW on, CH on, CH off) can control your system, but unless it is very unusual it should be fine.

Hive is marketed for use with gas boilers but it works perfectly well with oil (ours is oil) even though this isn't mentioned very prominently in the literature.

I installed everything myself because our CH engineer didn't feel confident to do the internet side of things. I checked the wires at the timer controller and thermostat and OK'd what I was planning to do with him and with my father-in-law who is an electrician. The longest task was the most trivial: working out how I was going to attach the controller unit in place of the current timer, because our timer had an old-style backing plate. Most modern controllers have a standard plate with the pins in a standard order so you just unhook the old controller and put the Hive one in its place.

One thing we've noticed. With the old system, we found that the interior temperature varied by about 3 degrees in a cycle during the day - the boiler didn't turn off until the temp was about 1.5 deg about the desired and then didn't turn back on until the temp had fallen to 1.5 below desired. With Hive, it's more tightly controlled and temp varies by only about 0.5 degrees - assuming you don't open doors/windows and that the sun doesn't heat the house!

Reply to
NY

Thanks for your feedback.

That puzzles me. Are you saying that the CH switch is a changeover switch with permanent live effectively connected to COM (although there isn't a COM terminal as such) so that CH ON is live when there is a call for heat and CH OFF is live when there isn't? I had assumed that CH OFF and CH ON were connected to a pair of volt-free contacts - independent of the mains - so that boilers which used low voltage switching could use them.

Anyone else care to comment on that?

That's what my programmable stat currently does, so it would replace that.

Thanks for the explanation of 'boost'.

I'm my own CH engineer! I have reasonably intimate knowledge of my system having fitted the wireless programmable stat when there previously wasn't a room stat in the system.

I assume that you previously had a mechanical stat. They have quite a lot of hysteresis compared with electronic stats.

Anyone care to comment on the other questions which I raised in my previous post - how SMS control works, and the implications of relying on an external server?

Oh, and one other thing I meant to ask: the Hive thermostat seems to be designed for wall mounting only. My current wireless stat can be wall mounted but is also provided with a stand. I sometimes find it useful to move it from room to room. Is there any reason why I shouldn't make a simple stand for a Hive stat, and do the same with that?

Reply to
Roger Mills

I don't have to pay true call, I can manage the list on the device after the free internet sub is over with. I found the internet a bit fiddly in any case. I see these remote heating things nowhave a skill for the Amazon Echo. Brian

Reply to
Brian Gaff

Since CH OFF wasn't relevant for me, I didn't actually test this, but I imagine you're right: CH ON is live when Hive is "calling" (ie actual temp is below required temp) and CH OFF is live when Hive is "not calling".

Certainly when it's installed in my system, CH ON is live when Hive turns on, thereby supplying power to the boiler to activate the burner and the pump for the CH.

Reply to
NY

They do indeed. My wife likes being able to lie in bed and say "Alexa, turn up the heating by one degree" or "Alexa, boost the heating for one hour". She thinks Alexa is great: we've also got a remote-controlled mains socket with a standard lamp plugged in, with an Echo "skill" so she can say "Alexa, turn spot on" (or off) - when we configured the name of the plug as "spot" (light). It means that when she goes downstairs early in the morning she can turn the light on in the lounge before she is goes downstairs.

As a bit of a gimmick I was demonstrating all this to my parents when we saw them at Christmas, looking at the lounge an my mobile phone through the security camera and then turning on the light - all from several hundred miles away :-)

We're not *really* obsessed with gadgets :-)

Reply to
NY

They will just withdraw the service when they have something different to sell.

Its much like them ceasing to support a boiler in order to sell a new one when spares etc. are still readily available from the manufacturer.

Reply to
alan_m

Hear hear. They tried that on me. Only they destroyed part of the boiler too.

Reply to
Bob Eager

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