Hive thermostat hot water cylinder wiring - missing valves?

Discussion in 'Electricians' Talk' started by tellme_why, Sep 15, 2018.

  1. tellme_why

    tellme_why Member

    I am considering replacing my potterton EP heating programmer with a dual channel Hive but the latter only show one two output in the manual: Heating switch and hot water switch.
    I have a system boiler with hot water cylinder, two valves and cylinder thermostat. No wiring instructions or connectors for the two motorised valves and cylinder thermostat available in the Hive manual.
    -where can I find proper wiring instructions
    -can I buy a junction box ready made to "extend" Hive controller and wire in the two valves and cylinder thermostat?

    Many thanks!
  2. Bazza

    Bazza Well-Known Member

    Your Hive will completely replace your existing programmer. The best place to connect it is to the wiring centre for the heating/DHW.
    You’ll need to discover what plan your system is wired to.
  3. The Teach

    The Teach Well-Known Member

    Assuming the existing system is wired correctly,hive/nest install is a straight forward half hour job :).

    Sometimes the EP programmer backplate is used to terminate/join many other wires,just means some additional alterations.

    tellme_why,have you considered having it fitted professionally ? shop around for a deal !
  4. MGW

    MGW Well-Known Member

    For some reason Hive does not publish complete wiring diagrams, you need to retain cylinder thermostat, Hive only replaces the room thermostat, if you look as a proper thermostat with geofencing like Nest they do give better wiring diagrams, however even that thermostat requires the installer to have some knowledge, specially with a modulating boiler.

    In general with pre modulating boilers it was easy, thermostat told the motorised valve what to do, then motorised valve told the boiler.

    As far as I am aware Hive is for old pre modulating boilers.

    With a modulating boiler the cylinder thermostat still tells the motorised valve what to do, and the motorised valve tells the boiler, however for room temperature there are two methods, either the thermostats built into the radiator valves tell the hub what to do, then hub tells boiler, or the thermostat built into the radiator tells the boiler directly what to do with the return water temperature.

    With the latter there is a problem in that without some thing extra the boiler will start to cycle as warmer weather arrives, to stop this you could simply manually switch it off, however a simple thermostat put in the coldest room with no outside door, and no alternative heating can do this automatic. However you need to select a super cheap thermostat to do this, idea is to reduce boiler cycling not increase it, so any thermostat with anti hysteresis software built in is unsuitable for this task.

    So with a modulating boiler Hive is not suitable, Hive is for old non condensing boilers where the only way to control them is by turning on/off, called mark/space, it is not suitable for a condensing boiler which to work has to modulate the output.

    I have looked at the MiHome Energenie in line relay MIHO014 with the idea of remotely turning the system on/off, as you alter temperature directly to the electronic TRV head, so no point having a remote control thermostat as it is not required and wrong sort of thermostat, however if you turn down the temperature in all the rooms, the boiler only fires up for a short time anyway which keeps domestic hot water hot, so no real point.
  5. MGW

    MGW Well-Known Member

    Hive and Nest with non modulating boilers is simple, however with a modulating boiler Hive is unsuitable and Nest needs access to the eBUS which for some unknown reason is often where seals need to be broken so often it needs some one who is gas safe that can test the seals are sound after replacement to install Nest.

    Hive is a cheap nasty smart phone controllable on/off thermostat, Nest also connects to a Smart phone, however it is miles different to Hive, although it can switch old boilers on/off, it is also OpenTherm enabled so with a OpenTherm boiler will modulate the boiler, (turn flame height up and down) giving a constant temperature, not just reduced hysteresis it has no hysteresis, it also has volt free contacts so will work with 99% of boilers, unlike Hive which can only switch 230 volt. Nest also can follow or be followed by the eTRV heads, so the only real thing in common with Hive and Nest are they are thermostats with a four letter name, Nest run rings around Hive, also EvoHome runs rings around Nest.
  6. tellme_why

    tellme_why Member

    Many thanks MGW for your very interesting explaination. Before reading your last I was thinking of retaining the current potterton EP programmer keeping the current wiring and just connect the hive ch and boiler output in series. I may have to add a relay because as you said hive in not free contact. On the other hand I am also considering to replace boiler with a new vaillant or similar hence I will have to check whether the latter is modulating or not. I am aware that a cycling boiler would reduce effeciency so I would rather avoid buying a thermostat with no modulating option. The issue is what thermostast should I buy then? Ideally I would like to have the wireless remote temp setting unit and the phone app. Currently my system does not have a thermostast, only a programmer and TRVs and feature abnormal consumption. So first step I am considering (as per advice in this forum) is adding a thermostast furst and maybe replace my old potterton 60e with a new Vaillant.
  7. Mike83

    Mike83 Well-Known Member

    Hive and Nest work on modulating boilers and non modulating boilers.

    Some smarts controls are now using open therm to increase the efficiency of the boiler even more. The stat will talk directly to the boiler to modulate rather than just turning on and off.
  8. Peter208

    Peter208 Active Member

    Hive does work well on the 60e
    I like that Hive and others are able to connect to Alexa.
    You will find that the app information about your home heating and the extra control that you get with a smart stat is a leap from what you have now.
  9. peter palmer

    peter palmer Well-Known Member

    Open therm, another "green" initiative to entice people to part with hundreds to save a couple of pence.
    Bazza likes this.
  10. MGW

    MGW Well-Known Member

    Hive has no ability to control the modulation of a boiler, Nest does.

    The question as to if you want it to control the modulation is another question. The modulating boiler can be modulated by the return water temperature, and you could use Hive as a simple switch, set the temperature high so it does not turn off for on, and very low for off.

    However for a house to maintain a steady temperature the thermostatic radiator valve (TRV) needs to control the temperature if the wall thermostat is not able to modulate the boiler. Other wise the boiler will need to switch on/off on a regular basis to control the temperature, this will waste energy and stress the boiler, but there is no argument it will work.

    If one looks at the ideal, then likely looking at fan assisted radiators, as we move from ideal then likely next best is something like EvoHome then we look at Nest next with the follow ability.

    However as we reduce installation costs further, one has to ask is it worth it? Much depends on how fast the home will heat and cool, I found that this house is a lot slower than expected, and any thoughts of geofencing are out as a result. I found using the TRV electronic head it will keep the room within 0.5 deg C of setting as long as boiler is running, however the anti hysteresis software means change setting from 16C to 20C at 7am and it is 11am before it reaches it, so have to set to go from 16C to 23C for half an hour then down again to 20C and then by 8am it is at the set temperature.

    So you would need to alter the temperature twice and although altering it once before you leave to go home is OK, to then have to stop and reduce is again would be a real pain, so I tend to use set times, no real need to do it all away from the home.

    Cooling is worse, switch from 22C at 9 pm and by 7am it had rarely dropped to the 16C minimum setting.

    If I was doing it all again I would still use eTRV heads, but not WiFi heads, and I would use two wired programmable thermostats to stop cycling. Either do it on the cheap, or use a proper thermostat like EvoHome, simply not worth going half way.
  11. peter palmer

    peter palmer Well-Known Member

    The only good thing about nest and hive is the ability to switch the boiler on and off remotely.

    Being able to switch the boiler off when you are away for the weekend after you have forgotten, or to delay switching it on if you are held up one evening will save a packet compared to all this fancy geofencing mumbo jumbo.
    Mike83 likes this.
  12. Mike83

    Mike83 Well-Known Member

    I didn’t say hive could control the modulation. I just said hive works with modulating boilers.
  13. MGW

    MGW Well-Known Member

    So will any volt free thermostat. However Hive is not volt free is limited as to what boilers it will work with.

    There are two basic reasons for having a wall thermostat.
    1) To stop system cycling when weather is getting warmer.
    2) To control temperature of home.
    With 1) you want a thermostat which does NOT have anti hysteresis software, so Hive not suitable.
    With 2) you need a home which is either open plan, or central heating which is blown hot air, otherwise a single thermostat is useless, and Hive can certainly control either as long as it does not require either eBUS or volt free connections.

    So there are very few British homes where Hive is suitable. However to be fair, many other thermostats are not really suitable for the home and system they are used on.

    Bosch Wave is an eBUS connected thermostat, however it does not connect to the eTRV heads so it will only get one room to correct temperature.

    To get all rooms correct there is only one way, and that is a thermostat in every room. It does not matter if it is connected to radiator valve, or boiler or motorised valve, each room needs it's own thermostat. Again it does not really matter if it uses mark/space ratio or modulation as if you have multi-rooms then likely at any one time one room will be demanding heat, so a modulating boiler can still work.

    However since in most cases where a modulating boiler is fitted we have TRV's also fitted it makes sense to use what we already have. So the main item used to control the rooms is the TRV.

    Now I would be first to admit a TRV with 1 to 6 marked on its body is unlikely to maintain a room at 20C plus or minus even 1 deg C, however the electronic heads will not only keep the room plus or minus 0.5 deg C to set temperature but can also have times programmed into them. The Terrier i-temp i30 is about the cheapest at around £18, this is not wifi, with wifi types often you need a hub as well, which bumps up the price, normally sold as kits, so EvoHome 4 room kit looking at around £500.

    The problem is non hysteresis thermostats with are wireless do not normally have fail safe system built in, so if you look at a basic system the wall thermostat must be wired, so around £34 for programmable thermostat which should be put in a room with no outside door no alternative form of heating, and the last room in house to get warm, in real terms often no such room, however you can get around this by fitting two thermostats in parallel they must then both be satisfied to switch off the central heating. So four electronic heads and two wall thermostats can in the main give varying temperatures as required throughout the week so for around £140 you can install a smart system which although not perfect is near enough.

    If you consider that as bargain basement then to improve on that system you have a huge jump in price, even Nest with 4 wifi valves £250 for valve heads, £53 for hub, and £200 for Nest and all in all not that much different to price for EvoHome and EvoHome gives a lot better control.

    So in real terms moving from non phone controllable to phone controllable with out losing basic control of every room means £350 extra to a simple timed system. As to Hive it is neither one thing or the other, it does connect to Phone but that is where it stops with advantage.

    It will not connect to eTRV heads, it will not connect to eBUS, so rooms will all vary in temperature and it will be stressing out boiler switching it repeatedly on/off, and each time it does that heat is wasted out the flue.
  14. peter palmer

    peter palmer Well-Known Member

    How can a TRV of any description reliably control the temperature of a room? they are sat about a foot from the floor right next to a red hot radiator.

    Best bet would be a thermostat in each room controlling only that rad, a bit like UFH. I've often wondered whether a UFH actuator head would screw onto a TRV instead of a manifold.
  15. MGW

    MGW Well-Known Member

    The eTRV head measures air temperature and water temperature, the latter is used to compensate for the heat coming from the radiator, since I have them I can confirm that works, and set to 20 deg C the room does settle at 20 deg C +/- 0.5 deg C.

    I have also wondered if the UFH head would fit a TRV base.

    I also tried to use a portable thermostat to control boiler using the original TRV to stop rooms getting too hot, but the portable thermostat would be moved to room in use.

    The hysteresis was a surprise, it became clear position is very important. It must face the radiator so natural thermals are circulating air radiator to thermostat, 90 deg to radiator and the hysteresis is huge. This left a problem facing radiator was a gas fire, and it was an outside wall so fixed on wall the room always hotter than the thermostat showed, experiment showed best was to set thermostat a little high, and put it on the table near to radiator, it seemed the closer it was positioned to radiator the less the hysteresis was, although of course one had to compensate for radiator heat.

    When the free standing thermostat developed a fault, I was loathed to replace with another one the same, so tried the eTRV head, I used MiHome Energenie and as far as keeping the room at temperature set, it was far better than the mobile thermostat.

    However where it failed was when changing the setting, clearly if set to raise temperature from 16 to 20C it can only do it when boiler is running. However although I could set programmer to start boiler at same time as eTRV head called for more heat, the anti-hysteresis software in the head reduced the speed at which the room heated up, so the boiler had turned off before room at new heat.

    To compensate the head was set to 22C for an hour then back down to 20C which in essence would override the anti-hysteresis software.

    This is the problem with the whole system, the times on the programmer have to match times on eTRV heads, and if I was to get a Nest wall thermostat it can be set so either Nest follows the eTRV head or the eTRV head follows Nest, not clearly as good as EvoHome where the thermostat actually uses the temperatures recorded by the eTRV, but the two systems do integrate.

    And this is where Hive falls flat, it simply does not integrate with any other system, it does not talk to boiler using opentherm, it does not connect in any way to the eTRV heads. So if it does not talk to the eTRV heads then you need to manually set times on both to match, so instead of one app on your phone you need two, and you have to set each radiator independently. Forget that for a game of solders.
  16. chippie244

    chippie244 Well-Known Member

    Hi MGW.
    I love reading your essays on heat control, in fact controls in general, and that you're so passionate about about it, we just open or close doors and windows or turn the heating on or wear a jumper.
    I'm never going to do it but do all your control systems save more money than they cost or is it just a hobby?
    Leaving a battery on charge for months and monitering it to see if it starts is never going to make money but I love that you do it.
    In no way am I having a go at you just curious about your motivation which I think itself is curiosity
  17. MGW

    MGW Well-Known Member

    The heating was forced on me, mother was 90 so needed to be right, hind sight should have fitted EvoHome it would have worked right first time, but I tried to save money, then felt guilty if I spent my mothers money correcting my mistake, so I was going to make it work.

    Battery very different, as a young apprentice we were given home work, it was explain why the battery voltage goes down, so into college library and tried to look it up. Could find loads on zinc carbon, but not lead acid, under load clearly internal resistance, but could not find why with two plates with a Electrochemical potential should not simply stay at 12.8 volt until fully discharged then fall to zero. I compared the lead acid to zinc carbon in home work and said I assumed the same process happened with both. I still don't really know the answer.

    However that sparked an interest with lead acid batteries, and in Algeria and the Falklands getting replacements was not easy, so any way to keep them going was tried. But back then there was no such thing as a smart battery charger.

    So when the 75 Ah battery was in error allowed to remain flat for an extended time, I connected the new smart charger from Lidi which I plugged into the energy monitor that I had been using to monitor a fridge/freezer used for brewing. Ideally looking at the computer web page, I realised it did not slowly recover as expected, but sat seemingly doing nothing for 4 days, then fully recharged in two days, so I had two ex-stair lift batteries, these had been left longer, this time seemingly doing nothing for 10 days, then fully recharged in 24 hours. So one battery left, just had to try it, been left flat for years, no way did I ever expect it to charge, however seemingly doing nothing for 3 months, it then recharged in two weeks, I will not say fully, as still taking a charge, and tests show much reduced current output.

    I tend to go OTT to learn something, then never or at least seldom use the knowledge, same with camera, spend ages learning how to do HDR, then moved on, rarely do HDR now.
  18. chippie244

    chippie244 Well-Known Member

    Brilliant :):)
  19. Peter208

    Peter208 Active Member

    I too enjoy all the info that MGW adds to a post.
    As for the bit about the battery, one of my car batteries went flat, would not take a charge from a smart charger. So, I connected some battery leads from a fully charged, spare car battery of the same type and size and left it for only a couple of hours then retried the smart charger......success .
    Back to Hive. For a simple, DIY exchange / upgrade to your homes boiler control, Hive and Nest are an easy fix. I never wanted to add wifi controlled TRV heads, too expensive and most, even cheap TRVs can be set to give a reasonable temp control to the room and thus a energy saving.

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