Missed defrost alarms.

[james 100]

I have just started working with RDM controllers linked to Honeywell Tuscan 5 controllers, I have two cases that are coming up with missed defrost alarms. Does anyone have any ideas, what am i missing? :confused:

[Silhouette]

On both RDM and Honeywell (ELM) controllers there is a setting "No Defrost Alarm" this needs to be set higher than your defrost seperation time i.e. if you have 4 defrosts a day they will be 6 hours apart, the no defrost alarm needs to be set for at least 7 hours so that when daylight saving (BST) comes in it will not effect the alarm. I tend to err on the high side with this setting and go for a 2 hour clearance i.e. 8hours!;)

[james 100]

Thanks very much, i will give it a try.

[coolhibby1875]

there are various reasons for missed defrost alarms, if the set up is for remote defrost ie gets the signal from the front end, and it goes off line a while it gives missed derfost alarm, if the times are diff from the front end than the controller you can get alarm, you might also find the tuscan has lost all its defrost times this will also give alarm, and the old favorite is if its using a termination probe ( probe 5 ) and its u/s ie above termination temperature it wont go on defrost thus giving you a missed defrost alarm, a lot of people set parameter no def to 25 this means you will never get the missed defrost alarm.

[cool runings]

.

As the others state it is not somthing to worry about.

It can be a result of the parameter settings combined with clock changes or manual defrosts.

Also it can result through communication problems.


coolrunnings.

[jwhytock]

best rule of thunb would be 4 def/ day i-e every 6 hours you would set no defrost time to miss 2 defrosts plus 1 hour = 13 hours so for 6 defrosts / day setting would be 9 hours 2 defrosts / day would be 25 hours and so on
some retailers e-g morrisons markys co-op insist on these being setup to inform of a missed defrost to prevent risk of ice up e.g cheers

[jwhytock]

see the spelling aint improving :eek:

[heatercreep]

I think its called the no def setting. It is the number of hours that have passed without local (internal) or remote (network) activated defrost. I have found that when a missed defrost alert occurs, it forces that case into defrost. On electric def this can cause a catastophic clash of defrosts!! It does seem like a mysterious fault at first


I have just started working with RDM controllers linked to Honeywell Tuscan 5 controllers, I have two cases that are coming up with missed defrost alarms. Does anyone have any ideas, what am i missing? :confused:

[CAPTAINBIRDSEYE]

Sorry to sound patronizing heatercreep but the parameter is definently called no defrost time ! cheers mate