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alanchow (Mechanical)
6 Nov 07 8:52
The client want us to design a 50% redundant HVAC system for them. In my opinion, 50% redundancy means we need 3 rooftop units with 50% capacity for each, anytime we just run 2 units to get 100% capacity and another one will be the backup, is that correct? Thanks.
imok2 (Mechanical)
6 Nov 07 11:37
In engineering: serving as a duplicate for preventing failure of an entire system. That said I would Have one unit for 100% load and another as a stand by.
MintJulep (Mechanical)
6 Nov 07 14:23
See FAQ403-1308: I don't understand something in my customer's spec, what does it mean?
alanchow (Mechanical)
6 Nov 07 16:37
thanks all. two unit each with 100% load means 100% redundancy. now the question is about 50% redundancy.
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cd122395 (Mechanical)
6 Nov 07 16:42
You need one AHU sized for 100% of the load and another backup size for 50% of the load. That is the 50% redundancy. Sometimes owners want this because they don't want to pay for two 100% units, so they feel that if something should go wrong with the main unit that they can get by on 50% temporarily until the broken one is fixed.
marcoh (Mechanical)
6 Nov 07 17:04
I just had a similar discussion with a client the other day andhe statement can be somewhat ambiguous and needs to be confirmed with the client. Their reasoning was:
- 100% redundancy means if anything fails 100% capacity is available, ie two units at 100% capacity, 3 units at 50% capacity, 4 units at 33% capacity etc
- 50% redundancy means if anything fails min 50% capacity is available, ie two units at 50% capacity are required (or 3 at 33% etc) 字串2
For this particular project the requirement was 75% redundancy so four units at 25% full load are being installed, if any one fail 75% capacity is available which is still sufficient for most of the time.
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