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Thread: HCM200 boiler demand short cycling when not required

  1. #1
    Automated Home Jr Member
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    Default HCM200 boiler demand short cycling when not required

    Hi

    I have recently installed an HCM200 system with 10 HR80 TRVs and a HC60NG as a boiler relay. This all seems to work fine with one issue remaining. This is that the HC60NG is switching on the boiler for 1 minute in (roughly) every ten for no apparent reason e.g. when every room is up to temperature or the temperature settings have all just been reduced (like last thing at night). I have reset the system to factory setting, lowered room settings to 13 degrees and tried changing any other parameters that seem to relate to this but all to no avail.

    I only really noticed because it is a condensing boiler with quite a noisy fan with a long overrun, but it is remarkable consistent.

    Has anyone else found this and possibly a fix for it?

    The parameters values at present are (started with defaults):

    Eco offset 3.0C
    eco thres 13.0C (was 17.0C so tried lowering to be sure).
    Heating setpoint 14.0C
    Boiler demand 18C (have tried 10 and 25)
    Frost protect 8.0C
    Setp. demand Off

    Room parameters:
    Local lock off
    Range 10-25C
    Optimization On (tried off too)

    Software v6.00 UK 22 Nov 2004 12:00
    433V13 868VA1

  2. #2
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    Default

    David,

    I've had exactly the same problem with my CM67z system (two CM67s, 6 HR80s) - see Tony's thread 'Honeywell CM Zone - basic questions' (top of page 2). Initially I thought it was caused by incorrect set-up of everything as there is very little documentation available on how anything more complex than the most basic system has to be configured. After several conversations with Honeywell and much experimenting I got things how they should be but still get the cycling probelm intermittently. The first solution is to reset the HC60 by clearing the memory and re-binding it to the controller(s). This seemed to work for a while but then the cycling started again - it seems to happen whenever I've made a change to the configuration settings of my CM67zs or done anything with one of the HR80s, but there isn't a clear pattern. After several conversations with Honeywell technical support about this they've asked me to email full details of my system and what's happening so they can take it up with their people - hopefully this will shed some light in which case I'll post details.

    Apart from the cycling how are you getting on with the HCM200? Did you buy it in the UK and did you install yourself? (I ask because I'm thinking of going down this route myself as one half of the house is still not covered).

    Cheers,

    Peter

  3. #3
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    Default General experience with HCM200 (and short cycling update)

    Hi Peter

    Many thanks for coming back to me. Most useful to know that I am not alone with this problem (see about half way down for a possible cause and solution for you).

    Do you have a contact at Honeywell that I could possibly pursue too?

    I have a second HC60 so I could try configuring that one as the boiler controller to see if it makes a difference, although I suspect that the problem lies with the HCM200 as I turned it off in annoyance early one morning and the demand signaling stopped. However, it then didn't seem to like communicating with the HR80s after that (well not within the next 30 minutes in any case, so I had to re-bind them all as it was getting a bit too chilly by then for everyone else in the house).

    I have re-bound the HC60 at least twice too, but haven't 'reset' it - is that in the instructions somewhere?

    *** Eureka, found the solution for you, I think! ****

    The back of the instructions for the HC60NG (which I had never looked at as I assumed it was just the same stuff in another language) states that there is a basic cycle time for the CM67 (section D 10). The default is to be on for 1 minute and to cycle six times per hour. You can change this setting by using the prog 2 key (Installer setup mode table B2 refers), but the lowest value is 3 per hour with a minimum on time of 1 minute.

    I cannot find the same options for the HCM200 and get the impression that the only way to achieve proper control with it is to use an HS30 as the boiler controller (not available in the UK though). It is not clear that the HS30 can be used in this manner with the demand being determined by HR80s instead of room setpoint controllers. Nor can I be certain that the HCM200 won't decide to cycle an HS30 in the same way it does an HC60! I probably will have to order some more bits from Germany to find out (rather expensive way of doing it though).

    So, for now I have wired my old boiler timer to provide power to the boiler via the HC60 so it is off overnight and during the day on weekdays. I have noted that the short cycling is very regular though but I must admit that I don't recall it happening from the very beginning though.

    The following post contains most of the information about the system that I have installed (not complete as yet). I bought the HCM200 from Germany (details in the post below too)

    http://www.automatedhome.co.uk/vbull...ead.php?t=1567

    i am currently controlling a hall and eight rooms with it.

    Other than that, here is a message that I sent to someone who contacted me directly about it.

    I have found it pretty easy to be honest once I got my head around the (not very difficult) concept of working to temperatures at times of day for each area, rather than being on or off and how to use the lifestyles (that you can only have one at a time and use them to change the settings of the devices within the lifestyle - you can set them for a time in the future, but I don't think that you can queue them up).

    I am only using heating with on-demand boiler operation only. The one thing I have not got sorted out is using a separate temperature sensor and switch for a room that has underfloor heating (mainly because I will have to get the sensor from abroad).

    The menu system is very straightforward, if a bit tedious sometimes and the push/rotate control knob works pretty well. Having set up one room you can copy it to another, or copy one day to the next for a given room.

    David

  4. #4
    Automated Home Guru MichaelD's Avatar
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    I've just been going through the detailed instruction sheet for the CM67z, and it has a parameter 16 which controls the actions if communications is lost. There is probably a similar parameter for the HCM200:

    "The CM67Z allows you to set the fail-safe mode of operation of the heating system if radio communication is lost. By default HC60 boiler controller relay will be switched OFF in case of communication loss. Alternatively you may choose to cycle the boiler at 2 min ON and 8min OFF. Useful when the building is not occupied for long periods of time and there is a high risk of frost damage."

    I wonder if you have parameter 16 set to 1, which will give you 2 minutes on in every 10 minutes if you've lost a connection? Sounds like that might be what you're experiencing. If so, change parameter 16 to 0 and see if it makes a difference.

    Let us know how you get on

    Michael

  5. #5
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    Hi Michael

    Many thanks for this; very useful.

    That does indeed sound very similar like what I am experiencing although I am pretty sure that it was only coming on for one minute rather than 2.

    The parameters appear to be quite different on the HCM200 though - they are all named and there doesn't seem to be the control options available for adjusting these parameters (all the parameters are named on the HCM200 and none have a name like that).

    However, I have another unit available so I might try a) linking that up with no radio signal to see what happens and b) connecting it but as a controller for some other purpose to find out what happens when it is notionally in the off state.

    Cheers

    David

  6. #6
    Automated Home Guru MichaelD's Avatar
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    David,

    I've read a lot of Honeywell PDFs today!

    It seems that it is the HC60NG that has the fail-safe setting. Honeywell seem to use this same boiler control box for a whole range of different systems, not just CM-Zone, and different thermostats have different ways to change the fail-safe mode.

    The following is from one of their kits with a single thermostat and boiler control.

    "The failsafe mode defines the receiver box [i.e. the HC60NG] output relay status if the RF communication is lost (e.g. when the room thermostat stops communicating due to discharged batteries). The factory setting keeps the
    relay permanently off when communications is lost. This can be changed to
    0 - when RF communication is lost the relay will be held in OFF position.
    1 - when RF communication is lost the relay output will cycle at 20% on 80% off."

    If the HC60NG hasn't heard from a controller for about an hour, it puts on a red LED, is that happening with yours?

    Also, there is a chance that your boiler is only coming on for 1 minute because there is some anti-cycling on the boiler itself, mine has that, so if its just gone off, it can't come on again for several minutes. If yours won't switch on until its been off for 10 minutes, that could explain your 1 minute on-times.

    Michael
    Last edited by MichaelD; 5th October 2008 at 03:16 AM.

  7. #7
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    Default HC60NG and HS30

    Hi Michael and all

    Sorry, I don't think that I replied to that last post.

    I finally got the HS30 and so have done a bit more work on this.

    1. I am pretty certain that the cycling problem is down to the cycles per hour setting on the HC60NG as its green light comes on and then the boiler fires up. I don't yet have a solution although the following ideas are available:

    a) Put a HS30 in series with it so that both have to be on for the boiler to fire (see more below about using the HS30 as a boiler switch though).

    b) Put two HC60NGs in series. This assumed that the cycle would be out of sync between them. Of course, it is likely that two of the same unit cannot be bound to one HCM200d.

    c) Use the wired output from the HCM200d to switch the supply to the HC60NG and hence to the boiler e.g. through my existing heating timer. I need to investigate when that output is set and what form it takes first.

    d) Carry on as at present with my timeswitch providing power to the switched terminals of the HC60NG only at only certain times. This would mean that both that timer would have to be activated to provide power if heat was required outside of its normal schedule.

    On using the HS30 as the boiler controller I have found that it lacks the 'intelligence' of the HC60NG. It works as follows:

    1. Install it as a boiler switch.

    2. Set the 'boiler setpoint' (I think that is the correct term on the controller) to a suitable value. 18C is the default, but I would go lower as I set my rads to 14C when off and to between 17.5C and 20C when on.

    3. When any radiator control value (HR80) has a temperature setting above the boiler setpoint the HS30 will be switched on. This is regardless of whether the room temperature is lower or even higher than the setpoint. To put it another way, as long as any HR80 has a temperature setting of more than the boiler setpoint (17C in my case) the HS30 will be switched on.

    This is hopeless as the boiler will essentially run the whole time, only cutting out when the water temperature though it hits the limit. It will refire as soon as the water temperature drops a bit.

    With the HC60NG the boiler will only be fired if the controller in a given room (or on a given rad valve) says that it needs more heat. Thus you get the benefit of a) the room actually being up to temperature and b) the intelligence in the HR80 (I don't know if they also monitor the water temperature too).

    So, forget about using an HS30 for boiler control unless you have an HC60NG in series with it!

    I hope that this makes some sense and helps.

    David

  8. #8
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    Default All working now


  9. #9
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    Default Solution

    Below is part of another thread on this subject. Folks, don't beat yourselves up with this problem - just work around it as below. I'm into my second heating season with no cycling, it really works well.

    The HC60NG has been cycling my boiler for some time now and slowly driving me crazy, so why I didn't think of this solution before now is a mistery !

    I've added a 'time delay' relay into the boiler control circuit. The relay coil is energised by the HC60NG when calling for heating, the relay contacts supply the boiler with 240v. The relay allows a variable time delay to be set between the coil energising and the contacts closing. I've used 10min as a delay time.

    If the HC60NG is simply cycling (as it tends to do, a lot) then the relay will receive the 240v feed, but the boiler will only start if the 240v feed exists for more than 10mins (in my case). As a result the relay filters out the cycling request and only starts the boiler when the controls are making a more serious request for heat.

    Boiler cycling has now completely stopped, the only very minor downside is that I have to wait 10mins before the boiler will start after a genuine request but this has actually not been noticed

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