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Do you recall if the HR92’s open to full if they lose communication with the Evohome and failsafe mode is activated, otherwise if they have no failsafe mode then the boiler will just cycle without heat to the rooms?
According to the HR92 ‘manual’ this happens in the event of a radio failure:
The room setpoint temperature of the HR92 radiator controller is changed automatically to 20 °C.
Didn’t want to speak too soon on the app, but has been working well for the past hour for me too :-)
Good oh - commissioned two systems in the last few days and its been a bit embarrassing explaining to the customer "sorry, Honeywell broke the app last week. It'll be back in a while".
Got 3 more to do next week and lord knows how many more coming up. Can't keep track of the orders.
Kind Regards - Dan Robinson (Jennings Heating Ltd)
Sorry when I say fail safe - to clarify - I mean "communication failure" mode.
Yes that's what I'm talking about too - so during a long term loss of comms does an HR92 only switch to 20/21 degrees if fail safe was configured or any time it looses comms for a long time ?
Yes that's what I'm talking about too - so during a long term loss of comms does an HR92 only switch to 20/21 degrees if fail safe was configured or any time it looses comms for a long time ?
Yes. So in essence if comms goes down, then the BDR91 80/20's the boiler. And BDRs throttle to 21 degrees (unless open window overrides - but I am checking that).
And to answer Hengus' question - open therm bridge operates same
getconnected.honeywell.com | I work for Honeywell. Any posts I make are purely to help if I can. Any personal views expressed are my own
Yes. So in essence if comms goes down, then the BDR91 80/20's the boiler. And BDRs throttle to 21 degrees (unless open window overrides - but I am checking that).
I've tested fail safe before but only back when I had no hot water control, so I thought I'd test it again now I'm using a 3xBDR91 S-Plan configuration.
So I set the controller to away mode (10 degrees for me) and waited 15 minutes until the pump overrun had definitely stopped. I then removed the batteries from the controller off the dock and waited...
For BDR91's the following happened:
0-50 minutes - nothing
50 minutes - the red light on all three relays started flashing.
60 minutes - the red light on all three relays went solid red and the green light on the heating zone valve relay came on and stayed on. No boiler relay yet though.
70 minutes - the green light on the boiler control relay came on and started cycling 2 minutes on per 10 minutes as expected.
The green light on the heating zone valve relay stayed on constant ever since then. This makes sense because without the controller to keep the boiler relay and heating zone valve relay in time with each other they would drift out of sync after a while and you would end up with them both running for 2 minutes but not the same two minutes... better to cycle the boiler relay and keep the heating zone valve relay on constant. I'm going to assume that in a two relay configuration it's the heating zone valve relay that cycles on and off however.
For HR92's the following happened:
0-30 minutes - nothing
30 minutes - "Syncing" appeared at the bottom.
60 minutes - "No Sync" appeared at the bottom. Also those HR92's in zones with remote temperature sensors reverted back to their internal temperature sensor at this point. The set point was still 10 degrees.
110 minutes - most of the HR92's changed to reporting "Comms" at the bottom, and both the wireless icon and an exclamation point in the top left started flashing. At this point they changed set point from 10 degrees to 20. (Not 21) A couple of straggling HR92's changed about 20 minutes later.
So it takes an hour of lost comms for a BDR91 to start cycling on and nearly 2 hours of lost comms before an HR92 changes its set point to 20 degrees.
What I did notice is that the 20% duty cycle was not enough for the rooms to warm much - they would never have got to their set points but hopefully it would have been sufficient to avoid freezing temperatures.
If you press the button on the boiler relay it changes from 20% duty cycle to staying on 100% - so if you were home and the controller failed you could do that. Pressing it again turns it off. When you turn it on or off with the button it stays that way without the controller to override it.
So anyone worrying about fail safe mode turning on your boiler unnecessarily, you would have to have pretty bad comms problems for no messages to get through for these lengths of time - and if you did, you really ought to get to the bottom of the problem as the system won't be functioning very well with such poor comms!
Last edited by DBMandrake; 22 September 2017, 01:57 PM.
Yes. So in essence if comms goes down, then the BDR91 80/20's the boiler. And BDRs throttle to 21 degrees (unless open window overrides - but I am checking that).
And to answer Hengus' question - open therm bridge operates same
Hi Rameses,
I assume when you wrote the ..”BDRs throttle to 21 degrees...” you meant HR92’s?
Also, good to see the TCC app issues resolved now.
I've tested fail safe before but only back when I had no hot water control, so I thought I'd test it again now I'm using a 3xBDR91 S-Plan configuration.
So I set the controller to away mode (10 degrees for me) and waited 15 minutes until the pump overrun had definitely stopped. I then removed the batteries from the controller off the dock and waited...
For BDR91's the following happened:
0-50 minutes - nothing
50 minutes - the red light on all three relays started flashing.
60 minutes - the red light on all three relays went solid red and the green light on the heating zone valve relay came on and stayed on. No boiler relay yet though.
70 minutes - the green light on the boiler control relay came on and started cycling 2 minutes on per 10 minutes as expected.
The green light on the heating zone valve relay stayed on constant ever since then. This makes sense because without the controller to keep the boiler relay and heating zone valve relay in time with each other they would drift out of sync after a while and you would end up with them both running for 2 minutes but not the same two minutes... better to cycle the boiler relay and keep the heating zone valve relay on constant. I'm going to assume that in a two relay configuration it's the heating zone valve relay that cycles on and off however.
For HR92's the following happened:
0-30 minutes - nothing
30 minutes - "Syncing" appeared at the bottom.
60 minutes - "No Sync" appeared at the bottom. Also those HR92's in zones with remote temperature sensors reverted back to their internal temperature sensor at this point. The set point was still 10 degrees.
110 minutes - most of the HR92's changed to reporting "Comms" at the bottom, and both the wireless icon and an exclamation point in the top left started flashing. At this point they changed set point from 10 degrees to 20. (Not 21) A couple of straggling HR92's changed about 20 minutes later.
So it takes an hour of lost comms for a BDR91 to start cycling on and nearly 2 hours of lost comms before an HR92 changes its set point to 20 degrees.
What I did notice is that the 20% duty cycle was not enough for the rooms to warm much - they would never have got to their set points but hopefully it would have been sufficient to avoid freezing temperatures.
If you press the button on the boiler relay it changes from 20% duty cycle to staying on 100% - so if you were home and the controller failed you could do that. Pressing it again turns it off. When you turn it on or off with the button it stays that way without the controller to override it.
So anyone worrying about fail safe mode turning on your boiler unnecessarily, you would have to have pretty bad comms problems for no messages to get through for these lengths of time - and if you did, you really ought to get to the bottom of the problem as the system won't be functioning very well with such poor comms!
Thanks for testing so we didn’t have to!! Good to see it works, and for failsafe purposes what you’ve described seems to be perfectly adequate.
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