FWIW I got this response recently on the Aquaponics Nation website regarding the NO solenoid and oxygen as backup in case of a power outage.

Hi Cecil,
 
I use this configuration in my designs all the time; NO selenoid valve for emergency oxygen. Can't advice on US model as I am down under. Hot coils and/or leakage are non issues, and my installations include demanding high line pressure and high volume units. I always advice that a facility has a spare coil in stock, as most good selenoid valves have a replaceble coil without taking the unit offline.
If you intend to have higher stocking densities I would advice to have a backup source AND emergency oxygen.
For small systems an inverter with a battery pack can run a circulation pump and airpump easy for a day. Last one I installed like this could run for 24 hours on 4 X 260 Ah batteries (with UPS/inverter); and then we were running; circulation pump, blower, oxygen generator, switchboard/contol gear.

One think more, motorized ball valves on oxy lines makes no sense. These are good for large bore low pressure applications.

http://aquaponicsnation.com/forums/topic/9510-oxygen-solenoid-source/

Last edited by Cecil Baird1; 10/20/15 09:58 AM.
If pigs could fly bacon would be harder to come by and there would be a lot of damaged trees.