Denco

[parky]

Anyone any ideas why a Denco D23XH with millenium controller fans just cut out and don't come on within the 30 sec time limit and trip system on air flow?:confused:

[Gideon Beddows]

Have you looked at the Start delay in level three software?

It may be set uo to 30 seconds to allow dampers to open somewhere or other?

Can you expand a little, i might be able to help? Is this from start up, or is the unit running and then it cuts the indoor fan out? is it the only unit in the room?
what is on the display when the fans cut out?

[Denco Technical]

Either start or function delay i suspect.

[parky]

Is the delay part of the microprocessor, the unit is running and goes onto hum mode then the fan cuts out and doesn't come back on inside the time limit.

[Denco Technical]

Yes, we have a start and a function delay:

Level three - Start delay & Level three Function delay.

As previously stated we use these functions so dampers have time to open and also we can stagger the machines so they don’t all start at the same time if there is site power constraints.

[Gideon Beddows]

Is the delay part of the microprocessor, the unit is running and goes onto hum mode then the fan cuts out and doesn't come back on inside the time limit.

does the unit go into DE-HUM? and the fans cut out?

[Denco Technical]

If its on De-hum only then i suspect the dehum relay has a broken pole, do you have the model and contract number so i can check the build sheets.

[parky]

Unit No is D23XH A47663, Unit is on Hum mode as it's trying to put heat into air as return air temp is 17oC and set point is 19oC

[Gideon Beddows]

i'll leave this one with you Rob? ;O)

[Denco Technical]

If the return air is 17 degree and you have a set point of19 then the unit will try regardless of what mode its in to heat the air backto the desired temperature.

Just out of interest does the room have no or very littleheat gain?

also i was under the impression you had a issue with the fans is this correct?

I will dig the drawings out now and post the relay numbers regarding the fans.



Its pretty rare that in a close control environmentthat the unit runs in heating as you should have a constant and steady heat gain for theunit to work against what’s the application?

[Denco Technical]

To check the fans on de-hum you will need to select the unit into a de-hum function (set the de-hum lower than the room conditions)

Then check relay KA2 and KA2a they should switch the motors onto the low speed pole, i suspect the relays are switching but not making contact and stopping the fans.

see drawing below:

[parky]

Thanks for that, I suspect you may be right about the relay as the contactor for de hum sometimes doesn't energise, there quite a bit of heat load in the room, it can get up to 29oC when units trip on this fault.

[Denco Technical]

Okay, let us know the outcome :)

[parky]

Changed the relays, system seems to be ok now. thank you for all your help:cool:

[Denco Technical]

Thanks for the message .... glad to see this site really works :)