Honeywell HCW80 / HC60NG Problem

[pat43]

Hi all, I've looked at all the other HCW80 / HC60NG problems - mines a bit different, I hope you can help...

When the room is up to tempereature, the HC60NG reciever switches the boiler off. Then 10mins later it switches the boiler on for 2mins. Then 10mins later it does it again...(and repeat!)

If i turn the thermostat up to 30 the heating stays on - i haven't waited till the room gets that hot. If i turn the thermostat down to 10 the heating stays off - it only does the 10min cycle when the room is at the set temperature ie room at 20, thermostat at 20.

When it does its 10min thing, the LED does not light on the HCW80 thermostat, just the green light on the HC60NG reciever.

I have turned off all other wireless electronics in the house to check for rogue signal (wireless internet, phones etc, even the tv remotes!)

This was fitted last week, i will be getting the installer back, but I wanted to check that its not supposed to do that, and that hopefully I could tell them what to look for - this will be their 5th visit due to tracing a fault with the old Boss units.

Thank you for any help you can give,
Pat

 

[D_Hailsham]

When the room is up to temperature, the HC60NG receiver switches the boiler off. Then 10mins later it switches the boiler on for 2mins. Then 10mins later it does it again...(and repeat!)

If I turn the thermostat up to 30 the heating stays on - I haven't waited till the room gets that hot. If I turn the thermostat down to 10 the heating stays off - it only does the 10min cycle when the room is at the set temperature ie room at 20, thermostat at 20.

When it does its 10min thing, the LED does not light on the HCW80 thermostat, just the green light on the HC60NG receiver.

Cancel the installer visit; the HCW80/HC60NG is working exactly as it should.

Read Honeywell FAQ: TPI Control

Your stat has a fixed cycle time of 10 mins, proportional band 1.5C, and a minimum on time of one minute.

I have been using a thermostat with TPI control for over six years and it keeps the house temperature rock steady at 21C. Sometimes the radiators are only warm, even in the coldest weather.

 

[pat43]

thank you very much - its put my mind at rest a bit. Its a bit annoying - my pipes creak when it comes on and off - i have to turn the tv up!

 

[D_Hailsham]

thank you very much - its put my mind at rest a bit. Its a bit annoying - my pipes creak when it comes on and off - i have to turn the tv up!

Sounds as if the water speed though the pipes is rather high. If you don't have a combi boiler, try turning the pump down from 3 to 2.

You may also find that the system needs balancing - read How to balance a CH system.

A quick balance can be obtained by setting all lockshield valves to half a turn open. Remove all TRVs leave for 10 minutes then feel how hot each rad is.

Choose on which in neither very hot or very cold and use is as a guide. Close the LS valve of the hotter ones by an eighth of a turn and open the LS valve of the colder ones by an eight turn and leave for ten minutes.

Repeat until all rads feel about the same temperature. Then replace the TRVs and set to the required temperature.

 

[Burnerman]

I'm using the same controls for my oil fired Heatslave 12/14.....I'd prefer if it didn't cycle so much as the burner has to go through quite an eleborate start up procedure, only to shut down again.
Also the hysteresis isn't as i thought......set the temperature to 14 deg and its still on at 18 deg........any comment?
John

 

[Dan Robinson]

Cycle times and such like are in the manual. Not sure if the CM6 range had a temperature offset but the 9 series do.

 

[Jezthered]

The HCW80 has set parameters. The CMT900 range has the ability to change the parameters, as does the DT92E so may be better with one of these.

 

[pat43]

thanks again - i'll give the balancing a try at the weekend...

 

[ianyork]

When the room is up to temperature, the HC60NG receiver switches the boiler off. Then 10mins later it switches the boiler on for 2mins. Then 10mins later it does it again...(and repeat!)

Cancel the installer visit; the HCW80/HC60NG is working exactly as it should.

Read Honeywell FAQ: TPI Control

Hi guys,
I have the same behaviour from the system even when there's no demand: while the temperature is falling or the heating is set lower than the ambient temperature the 10 minute cycle still happens. Is that a cause for calling out the installer?
Cheers,
Ian

 

[D_Hailsham]

I have the same behaviour from the system even when there's no demand: while (a) the temperature is falling or (b) the heating is set lower than the ambient temperature the 10 minute cycle still happens.

I've never noticed this happening on my system.

(a) Why is the temperature falling - e.g heating turned off?

(b) How much lower has the temperature been set, e.g 1 degree lower?

Does the cycling continue all the time (i.e until the heating goes on again or temperature turned up) or does it eventually stop?

 

[ianyork]

Thanks for the fast reply.

(a) Why is the temperature falling - e.g heating turned off?
(b) How much lower has the temperature been set, e.g 1 degree lower?
Does the cycling continue all the time (i.e until the heating goes on again or temperature turned up) or does it eventually stop?

(a) Exactly - the heating is turned off at the control unit
(b) More than 10 degrees. The controller is set to 5C and thermometers read 19C.
The cycling only occurs during the "rest" periods when there's no demand from the thermostat. If the rooms are heating up, the boiler fires continuously until the desired temperature is reached.
Just to make sure the binding hadn't been lost, I reset that successfully following the manual instructions; and all other control functions seem to be normal.
The first occurrence of the problem was after a power cut, and I wonder if the controller is now in an abnormal state. There doesn't appear to be a process for checking this or resetting the unit.
Any ideas?

 

[D_Hailsham]

I think this is one for Honeywell.

Email Honeywell

 

[ianyork]

We'll resort to manually switching off at the boiler rather than using the controllers when the heating is off, because otherwise the boiler fires every 10 minutes for a minute as if it were stuck performing the TPI hysteresis convergence process.

Here's the process for resetting the controller, supplied by Honeywell. Note step 2 which isn't in the user manual (although it is occasionally mentioned elsewhere in this forum).

CMZ REBINDING UNIT – RECEIVER BOX

THE BINDING OPERATION DESCRIBED BELOW IS REQUIRED IF:

Any of the system components (room unit or relay box) are replaced.

HC60NG has incorrect or no binding data stored (e.g. when pre-bound system pack components have been mismatched)
Interference with the RF signal has caused a communication failure

During the binding procedure keep approximately 1m distance between the room unit and the HC60NG

1 Turn off mains supply to HC60NG for 10 seconds. Re-connect supply.

2 Press and hold the HC60NG push button for 15 seconds to reset previously stored data. The red LED will start to flash at 0.1 s on/0.9 s off. Release the push button.

3 Press and hold the HC60NG push button for 5 sec to enter the binding mode. Red LED flashing at 0.5 s on/0.5 off confirms the binding mode has been entered.

4 Turn the CMZ unit off, press temp up, temp down and program button 1. Ins Z1 should be displayed.

5 Press the Suitcase button, a flame should appear, press z1-z2 on the right hand side.. The red LED is switched off on the receiver box to confirm the successful binding operation.

Honeywell have asked that I measure the voltages on terminals A & B as part of the next diagnostic step. Am now off to buy a voltmeter.

 

[D_Hailsham]

Honeywell have asked that I measure the voltages on terminals A & B as part of the next diagnostic step. Am now off to buy a voltmeter.

The results will depend on whether the HC60NG is fixed to the back plate!

HC60NG Removed
If you have a link between terminals L and A, your boiler is turned on by applying 240V to the switched live terminal. There should be 240Vac on A and 0Vac on B (measure to terminal N), when the power is on.

If there is no link between L and A, there will be either 240Vac on A or B or a much lower voltage (often 24V). This will depend on how the installer has wired the system.

HC60NG attached
You can't measure the voltage directly, so you will have to trace the cable back from the HC60NG backplate to the terminal box. Then check as above.

 

[ianyork]

OK so I think we have solved the problem. There were actually two issues that we've identified.

The first is that there was a dodgy relay in the HC60NG. Honeywell supplied a replacement that simply substituted for the existing removable unit. That changed the behaviour of the system noticeably, such that the interval between the boiler firings became highly variable (between 10 minutes and an hour).

We then found a radiator controller behind a radiator cover whose batteries were not making a good connection so the unit believed the batteries were depleted. When any one of the radiator controllers in our system has depleted batteries (blank screen), we find the boiler fires intermittently in the way described above. Once this behaviour was consistent, we "knew" there had to be radiator controller with "flat" batteries.

We've now decided to remove all the batteries from the radiator controllers when the heating is not in use during the summer, because (especially) the valve cycling depletes them and then causes the boiler to fire.

The boiler is now no longer firing continuously, or in fact at all for the heating system. It's just running the hot water now. So the result we wanted.

One potential improvement to the Honeywell system would be to have a "low battery" warning on the CM67z, showing which zone the unit is bound to. That would save having to check potentially every radiator unit, which in our case would be great because seven of them are behind radiator covers and a pain to get to and the rest are spread over 3 additional floors.

Thanks for all the help and advice.