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Phil, Shop owner
Category: Australia Whitegoods
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Experience:  Degree, Mech. engr. shop owner. 51 years experience
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We are controlling about 80 Daikin units for a DEMAND

Customer Question

We are controlling about 80 Daikin units for a DEMAND RESPONSE Program via a DELTA Controls BACnet BMS. All points are mapped perfectly and we are communicating with the DAIKIN units - (that was a huge challenge to stabilize the network). We can manually enable and disable the compressor to Start/Stop thru the BACnet BO ("Force_Thermo_Off_Command") and it works fine but for some reason when we issue a command from the DELTA system via software to enable / disable the compressor's BO on the DAIKIN system refuse to accept the command. Any suggestions?
Submitted: 2 months ago.
Category: Australia Whitegoods
Expert:  Phil replied 2 months ago.

Hello and Good work so far!

Daikin is not set up to interface directly with most BMS system outputs... the solution is to control a relay that you fit onto each daikin unit, and use the contacts in that relay to interrupt the Daikin controls power output to the compressor speed controls (if those are the inverter models)...or other controls feed to each compressor if those are not the inverter models.

Your BMS system vendor will sell such relays compatible with your BO.

Its time to locate the 'Finish and rate' link, that is the only way the company pays me for my time and expenses, in exchange I will hold the question open for any follow up that you might need, thanks!

Customer: replied 2 months ago.
Thanks for trying but your answer completely avoids my question. Diakin units are BACnet and my question is how to get the DAIKIN unit to accept the control command. I guess you cannot answer my question?
Expert:  Phil replied 2 months ago.

Hello again, here is a little about myself that might shed light on this BMS issue.

I began with Johnson Controls, Sacramento California office, designing pneumatic controls systems for large buildings and industry just as the very first electronic interface controls were coming on the scene. 1972 approximately.

The first IO alone was massive... since then things have gotten smaller but not less complex... indeed they have gotten more complex.

I am 100% in favor of controlling all functions of a remote machine through the BACnet controls system... but ONLY if does not get too complex with 90 smaller systems attached so that one failure can affect the entire building, and rocket scientists have to be flown in to sort it out at $250 an hour...with a two day wait time.

Meantime 90 tenants will be fuming at the designer and the building owners and management. These will not so gleefully pick up the horn and let you know that are, err a few little problems.. which are costing them tenants.

Accordingly I attempt to follow the KISS principle (Keep It Simple Stupid) whenever possible, especially when it comes to controlling small complex systems remotely. Something like a Cadillac with 16 power ashtrays... too much is too much if the ashtrays all start opening and closing every time you turn the windshield wipers on.

A while back I was called in to debug and provide analysis on the Denver Air Ports now infamous luggage handling system that had cost the air port 20 million in lost revenue, as luggage was slung off of the conveyor system and out onto the work crews from high over head.

Baggage jams were occurring twice a day (I did the math on that for them, related to their bragging rights that they had over 10,000 interface devices and relays all with a 99.99% reliability rate)

That was my first clue.

You can do the math on 10,000 of those devices with a 0.01% failure rate, and see plainly where the two disasters a day was coming from.

Long story short, I prefer the simplest possible relay connection to the peripheral units wherever possible, even at the expense of some monitoring bells and whistles, so that when a unit fails... diagnosis is not complicated beyond belief, and so that a failure of the primary controller will not shut the peripherals down with no means of bypass.

Lacking that, the buildings operating engineers (who are not electronics guru's as a rule) have the pleasure of wading though this 138 page manual... my view is that such is not viable.

Good luck with your project, if you have trouble with it later I will be available to remediate if needed, Meantime I will opt out in the hopes that you can find a more accomplished BACnet guy.

Expert:  Phil replied 2 months ago.

Hello again, I see than no one else has picked this question up, its a but complex and in the industrial sort of arena, not a lot of people have that experience.

You can send me a link to the interface controller that you cannot get to work with the daikin units along with the full model number of the Daikin units or a close up well focused photo if the Daikin unit wiring diagram and I will look it over for you.

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