Backup petrol generator sizing for stormwater pumps

Flash option would be to get a LPG generator like the below, use it to back up the whole house (Light use only as 33A limit). Have gasfitter set up a 2x45kg bottle install for emergency use, and have the ability to run on BBQ bottle for testing / maintenance running.

Not quite sure what flow rate's, and head you are dealing with, But if head is less than 4m (not eccentrically to drain it the correct place, but to dump at an emergency point, into a garden or whatever, some cheap options could be worth considering:

- Install a manual Gusher style pump. Fairly Cheap, can do 100L/m. Given you are going to need to be present to start the generator, could well be viable to man a pump. More reliable, and not maintenance running needs like a generator.

https://www.marine-deals.co.nz/whale-gusher-titan-manual-bilge-pump-bulkhead-mount

- Install a 12V system. Get the following:

Lighlty used say 100AH deep cycle battery ($150 - trademe)
Smart charger - $60 - $160
Cira '3500GPH" bilge pump or two (3200L/h per pump at 4m head) $110 each https://www.marine-deals.co.nz/bilge-pumps/seaflo-series-3500gph-submersible-bilge-pump-12v
Float swith or two (cira $50) - set above trigger point of the AC pump as to not wear out the 12v pumps quickly.
Bunch of wire, fuse holders, pipe etc.
Custom, extra long set of jumper leads to reach your driveway.

System would function fully automatically for a few hours untill the battery went flat if power went out during a rainstorm when you weren't home (cira 20A draw per pump on the 100AH battery).

System would be auto re-setting. - would charge it self back up when power came back on.

System would act as a redundant backup for the AC system if it failed for a reason other than a power cut (say the discharge pipe became disconnected). - With run time limited by the ability of the little charger to keep the battery charged.

In the event of a power outage / rainstorm when you are home, you could move a car to the driveway, connect the jumper leads between the deep cycle battery and you car battery, and leave the car to idle. Most cars will produce 20- 50 amps at idle which should be enough to give you continuous running from one big bilge pump at least.

Even with the fuel light on, most cars will idle for several hours, but if you were worried you could keep a jerry can of fuel.

If worried about security (never run car with engine inside garage), you could get a wheel clamp for the car, or see if you can lock the doors with a 2nd key with the engine running.

KiwiME

Scott3