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Replacing a faulty CH Receiver/Relay Unit (Honeywell HC60NG?)

Discussion in 'Plumbing and Central Heating' started by Robert Norman, 16 Oct 2020.

  1. Robert Norman

    Robert Norman

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    Hi

    Can anyone help please? I have (what I think is) a Honeywell HC60NG Receiver/Relay unit that has failed. Despite the fact that I have their “top of the range” boiler and CH cover, SSE Home Services are refusing to cover the cost of replacement because, they say, the unit is obsolete and replacing it with the current equivalent would count as an upgrade (which my policy does not cover).


    I see that some people are selling Honeywell HC60NG Receiver/Relay units on ebay, etc. and I’m wondering if I could just get one of those. My concern is that, where ebay sellers include a photo of the PCB, it looks different to mine.


    Also, the Receiver/Relay unit needs to work/be compatible with my thermostat/programmer unit (which is a Honeywell CM67NG – See Photos 4 and 5, below).


    The outer cover is shown in Photo1.


    As you can see in Photo2, the inside of the Receiver/Relay unit box on my wall says “R6660D”.


    Photo3 shown the PCB from inside my Receiver/Relay unit.

    Most of the sellers on ebay don’t include a photo of the PCB but, of the ones that do, almost all show a different PCB to the one in my unit (please see Photo6). This fact, in particular, is why I’m concerned about simply buying one off ebay and plugging it in to the existing socket on the existing box on the wall).
     

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    Last edited: 16 Oct 2020
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  3. ericmark

    ericmark

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    I seem to remember there was a frequancy change so to be safe need to replace both base and thermostat.

    You don't show picture of thermostat, could it be a simple flat battery.
     
  4. Robert Norman

    Robert Norman

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    Hi ericmark. Thank you for your response. As with other cases I’ve read about with faulty HC60NG units, it does work momentarily and fires up the boiler but won’t stay on (so not just a flat battery, unfortunately).

    NB. I have tried re-paring the receiver and thermostat but that made no difference.
     
  5. Chris_W

    Chris_W

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    The ones on ebay are approx £70, why not just get a whole new wireless room thermostat?
     
  6. lloyda

    lloyda

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    Removed this one last weekend. Working fine. Display had failed in CM927
    PM if you are interested. Certainly would not expect £70 for it!

    16028834016875069760830782947552.jpg
    16028834970626006694066010316114.jpg
     

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  7. Robert Norman

    Robert Norman

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    Hi lloyda. Thanks for your response.

    The thing is, the unit in your photo has a different circuit board to mine so I don’t know if it will be compatible. Do you know? I rather not have to swap out the back box (redo the wiring, etc.) and just slot the new cover and pcb into place on the existing box (if poss).
     
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  9. Chris_W

    Chris_W

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    If it turns out to be receiver, then you’d have to do it anyway? It’s 2 wires only, so should be easy enough.
     
  10. lloyda

    lloyda

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    The only real difference I can see is the manufacturer of the relay (red on mine). Can you read the part number of the PCB adjacent to e large blue object?

    Both units have part numbers of R6660D. I'm pretty certain that Physically my unit will fit your back plate.
     
  11. ericmark

    ericmark

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    The unit has a fail safe, so if there is a flat battery it can't fire up boiler and leave it on for an extended time due to loss of wireless link, that is the bit I likely with the old thermostat, however it also had anti-hysteresis software which caused it to use a mark/space ratio as it approached the set temperature, which with an old boiler or oil boiler was good, but with a modulating gas boiler this defeated the boilers own system, so resulted in boiler running in an uneconomic way.

    There are two reasons for a wall thermostat, one is to control the temperature of a room, the other is to stop the boiler cycling. The thermostat you have was designed to do the former, and did it very well, however we tend today to use modulating boilers and TRV heads to control the temperature, however the TRV method has a flaw, as summer approaches it turns off the boiler as the warm water returns, but only way boiler can know if it needs to turn on again is to fire up every so often and circulate water and detect return water temperature.

    So the idea is you fit a wall thermostat in a room normally kept cool, on ground floor, with no outside doors or alternative form of heating, so as summer approaches it can turn off boiler and stop it cycling. It is set slightly higher that the TRV so in winter it never turns off.

    If the boiler turns off due to return water being too hot, it turns off when already running at lowest output so not much heat lost out of the flue, and turns back on again at low output so does not over heat any radiator that the TRV has opened on, but if the wall thermostat turns the boiler off/on then it turns off at more than minimum output so more heat lost out of flue, and also turns on again at maximum output so more likely that a radiator will over shoot.

    Cure using a wall thermostat is to use one connected to boiler ebus, for example OpenTherm, so the wall thermostat slowly reduces or increases boiler output, it does not simply switch on/off. The other way is for the wall thermostat to use algorithms to work out when to turn off so the retained heat in radiators is just enough to hit target without over shooting, so the thermostat switches less times during the day so less heat lost out of the flue.

    The problem is the old style still works, but does not work as efficient as new style with a modulating boiler, the other method is to use wifi links to the TRV so the wall thermostat works more like a hub than a thermostat collecting info from the TRV's.

    With my oil boiler the old Honeywell thermostat is still a very good option, but the likes of Nest with either OpenTherm or cleaver algorithms is better with today's modulating gas boiler, however the government muddied the water, asking for zones, well more down to how the regulation was interpreted. Some councils I see count TRV heads as making zones, but many builders included zone valves in their design so you can control two floors independent, rather short sighted as with a four bedroom house likely bedrooms will be used by children to do home work in, or used as an office or craft room, so having whole upper floor on one zone rarely works, and as far as I can work out only EPH make wall thermostats using OpenTherm that work in a master/slave configuration to be able to efficiently run floors zoned that way.

    So we now have a host of wall thermostats and TRV heads which it seems are not interchangeable. Once you buy one make your locked in to continuing with that make, I feel I made an error with Nest as they have withdrawn their support for Energenie TRV heads.

    It seems it's a complete mess up, each make going their own way, OpenTherm seems the only thing they have adopted which allows some interchangeability.

    I have made mistakes with late mothers central heating, I looked as the spec and decided a Horstmann HRFS1 was a good option, it was programmable so I could set different temperatures through the day rather than simple on/off of the programmer, however it lost rf link, and left boiler running, unlike the Honeywell it did not have a fail safe.

    It seems with gas, which since I now have oil it does not worry me any more, but with gas either you use cheap hard wired, or expensive algorithms to control the mid price range wireless don't seem to be suited for gas. At least modern gas.

    You have not said what boiler you using so that thermostat may well be ideal, but would say now it the time to consider how to control in the future, and I hope you don't make same errors as I made.
     
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  12. Robert Norman

    Robert Norman

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    @ericmark. Thanks very much for taking the time to put together that very thorough explanation. You obviously know a lot more about this topic than I do. I’m a complete novice and know next to nothing about heating systems, boilers, etc.


    I suppose this might be a good time to replace the controls with something more modern but seems a shame as I was perfectly happy with how it was all working before this happened.


    NB. My boiler is a Remeha Avanta Plus 35c
     
  13. ericmark

    ericmark

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    I added installation manual to name of boiler and got this manual the first move was select find and type in OpenTherm and it got a result, so it would seem you have a number of options.
    1) Stand alone OpenTherm thermostat like Nest.
    2) Multi OpenTherm thermostats linked like EPH which would work better if already zoned.
    3) An OpenTherm hub/thermostat that links to TRV's
    4) A very simple on/off thermostat set simply to switch off boiler as weather warms up. Or even simple on/off switch.
    There is no simple best, and you do need to consider cost.

    So lets for start say simple on/off switch, then the TRV controls room temperature, maybe not ideal, but I will relate what happened to me, late mothers house the heating worked but rooms got both too hot and too cold.
    Idea 1) was a wireless thermostat I could move around, but it did not work, not helped when mother cleaned up and put it in a draw.
    Idea 2) Was an electronic TRV, I selected Energenie with idea latter of adding Nest, and at first it did not work very well, but realised it was the lock shield valves being on supply side instead of return, so radiator heated up too fast, so PC shows target and current, TRV_report.jpg so I slowly opened or closed the lock shield until they both showed the same on all four fitted, I then started moving one head around to other radiators, and setting the lock shield on that one, once done the old TRV was put back on, and once set each room was spot on, so never bothered getting Nest it worked well enough without.

    Now house 2, I moved house and new house had an oil boiler, and when I came to look, there was no thermostat in the main house and the programmer which should have allowed us to select DHW or CH once or twice a day seemed to do same what ever I did, and on investigation found I had to go down steps outside house into the flat underneath main house and plug in or unplug the pump. I realised the problem was three core and earth cable, but only two cores working, so I wanted to control both DHW and CH with two wires only, so I fitted Nest Gen 3, but not because it was a smart device, it was simply as could get all the control I wanted with just 2 wires.

    I had brought the Energenie TRV heads with me, but just 4, and 14 radiators, not worried about flat so bought 5 bluetooth eQ-3 TRV heads at £15 each. Well to be frank they are just as good as the Energenie, and although bluetooth helps setting them up, there is a non bluetooth version at £10 each. So I have 9 programmable TRV heads.

    I found once I had a TRV which was set °C and not some silly *123456 as on original heads, everything fell into place. Idea was to link the Energenie to Nest but it did not work, we simply have the same schedule set on both TRV and wall thermostat, it is not linked.

    OK the geofencing is nice, heating auto turns off when we go out, and back on before we return, no fiddling around with phone to set it, it's all automatic. And in the summer I look at temperature of room with TRV and decide if to turn on the AC before returning. But did not get it with that idea in mind.

    I would suggest you get some eQ-3 heads and try them, if not good enough then use them in bedrooms and get some linked TRV's to wall thermostat, but the Drayton system is not cheap, and I would say a cheap £35 wired programmable thermostat is worth a try, if it don't work not much lost, so worth a try, unless you want something like Geofencing anyway.
     
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  14. Robert Norman

    Robert Norman

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    @ericmark. Thanks for all that additional info. I'll give it some thought and decide (one way or another. Cheers!
     
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