100% redundancy question for HVAC system
100% redundancy question for HVAC system
(OP)
Hello all,
If there is a specification requirement for a "100% HVAC redundancy requirement", what would you consider in terms of redundancy? Let me explain further.
For our particular situation for a small building that contains 2 rooms, each with AHUs capable of handling 100% of the load for that room, but they are all controlled from a central PLC. This PLC is not redundant, in the sense that if it fails, the system itself will fail.
The customer specified that "the HVAC system shall be 100% redundant".
From your position, how would you see this in terms of system design? We have interpreted it in the sense that the AHUs are designed such that if 1 of the 2 units fails in the room, the other unit can pick up the heating/cooling requirements. The customer interprets this as needing an additional PLC.
My argument is that where does redundancy stop if they go by that definition? Do we provide multiple AC/DC feeds to the units, multiple controller control cable paths, etc. I think the specification is poorly written and there are no grounds to enforce "100% redundancy" without a solid definition of exactly which components must be redundant.
Any ideas? This is coming from an electrical guy, so I would like to hear feedback from the community's experts in the field.
Thank you!
If there is a specification requirement for a "100% HVAC redundancy requirement", what would you consider in terms of redundancy? Let me explain further.
For our particular situation for a small building that contains 2 rooms, each with AHUs capable of handling 100% of the load for that room, but they are all controlled from a central PLC. This PLC is not redundant, in the sense that if it fails, the system itself will fail.
The customer specified that "the HVAC system shall be 100% redundant".
From your position, how would you see this in terms of system design? We have interpreted it in the sense that the AHUs are designed such that if 1 of the 2 units fails in the room, the other unit can pick up the heating/cooling requirements. The customer interprets this as needing an additional PLC.
My argument is that where does redundancy stop if they go by that definition? Do we provide multiple AC/DC feeds to the units, multiple controller control cable paths, etc. I think the specification is poorly written and there are no grounds to enforce "100% redundancy" without a solid definition of exactly which components must be redundant.
Any ideas? This is coming from an electrical guy, so I would like to hear feedback from the community's experts in the field.
Thank you!





RE: 100% redundancy question for HVAC system
But, why is a PLC needed when a setback thermostat can do the job?
Keith Cress
kcress - http://www.flaminsystems.com
RE: 100% redundancy question for HVAC system
It sounds like your customer knows what they want, I would suggest talking with them and getting a firm understanding of the drivers behind why they are after "100% redundancy". This should inform the final solution.
RE: 100% redundancy question for HVAC system
As regards to electrical redundancy, you simply need to look at the specs - does AHU system spec included power supply or not. If not, than electrical supply redundancy is not covered within AHU redundancy requirement.
RE: 100% redundancy question for HVAC system
RE: 100% redundancy question for HVAC system
RE: 100% redundancy question for HVAC system
N+1, N+N, and whatever else.
The power supply to the building is more likely a single power source. AHU's are connected to the same electrical panel, etc.
If owner means zero interruption, then we are talking emergency generator for AHU and heat removal source (chillers, Condensing unit, controls) on emergency power.
Standard understanding in industry is Two AHU's, each with dedicated control panel.