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[Rob Spence]

Thanks Tim, more great info! Here on Vancouver Island we don't get very cold, so probably won't be a factor.

One of the affected parties in the neighborhood is donating a 100lb propane tank to the cause, we'll get the propane company that delivers to our house to do refills.

Tomorrow I'll talk to the local company who installs and services home back up units armed with more knowledge!

Thanks,       Don

A 100lb tank doesn't go very far. A 100 gal (nominal 125) is good. I have 2 of the 125 gal tanks for my cooking and the Generac 20k unit. My tanks cost me $500 each brand new.

You need to read the fuel consumption specs for the generator to be sure you have sized everything right. Download the install manual or if you can't find it, call Generac and they will email you a PDF.

Be sure you get the right transfer switch. It wants to be compatible with the genset for auto start and switchover. I suspect there is only a small difference in cost to have a unit that can handle the whole pumping subsystem versus thanking a chance on a hack to run just one pump. How will the controller know to only select the pump with power? I would want this to work unattended since Murphy will have the power fail while y'all are out of town.




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[Stephen Swaffer]

 A few quick rough searches yielded the following info:

Generac 8 kw genny requires 34 cu ft/hour at 50 % load.  At 2500 BTUs/cu ft that works out to 85000 BTUs/hour demand.

A typical 100 lb cylinder can supply 79,700 BTUs at 60 deg F,  that drops to 70, 700 at 50 deg F.

I am not an expert on propane use by any means it seems like a 100 lb cylinder will not adequately supply a genny-ultimately you have to be able to vaporize enough fuel quick enough or you will "run out of gas" even with propane in the tank.

Allowing the system to run only one pump should be simple enough-simply use an ice cube relay across utility power to disable a second pump.

The comments on starting a pump are correct-a typical motor can require 2 to 3 times the full load amps at start up.  It would be wise to verify that the genny you are wanting to install has the peak capacity to handle the pump start up-and if you decide to run both, you need to add that peak capacity to the running amps of one of the pumps.  An electrician should be able to tell the actual start up amps=but that can be affected by the actual generator output voltage.
 

[don mcmeckan]

A few quick rough searches yielded the following info:

Generac 8 kw genny requires 34 cu ft/hour at 50 % load.  At 2500 BTUs/cu ft that works out to 85000 BTUs/hour demand.

A typical 100 lb cylinder can supply 79,700 BTUs at 60 deg F,  that drops to 70, 700 at 50 deg F.

I am not an expert on propane use by any means it seems like a 100 lb cylinder will not adequately supply a genny-ultimately you have to be able to vaporize enough fuel quick enough or you will "run out of gas" even with propane in the tank.

Allowing the system to run only one pump should be simple enough-simply use an ice cube relay across utility power to disable a second pump.

The comments on starting a pump are correct-a typical motor can require 2 to 3 times the full load amps at start up.  It would be wise to verify that the genny you are wanting to install has the peak capacity to handle the pump start up-and if you decide to run both, you need to add that peak capacity to the running amps of one of the pumps.  An electrician should be able to tell the actual start up amps=but that can be affected by the actual generator output voltage.

Thanks Rob and Stephen, I finally have a meeting tomorrow with my bass playing electrician. When we chatted today he suggested we just use a gen that powers the existing breaker, which is 60 amps.

Rob we'll most likely get a genny / transfer switch combo.

This electrician has installed several Generacs, he likes them.

Stephen you're probably right about not doing a cheesy one pump affair, but one of our affected neighbors probably won't want to spend ANY money on this.

We're willing to foot the cost between as few as two of us, but if we can get something reliable for as small amount of money as possible, we might get everyone to kick in.

I'll report back tomorrow.

Thanks,       Don

[Rob Spence]

A few quick rough searches yielded the following info:

Generac 8 kw genny requires 34 cu ft/hour at 50 % load.  At 2500 BTUs/cu ft that works out to 85000 BTUs/hour demand.

A typical 100 lb cylinder can supply 79,700 BTUs at 60 deg F,  that drops to 70, 700 at 50 deg F.

I am not an expert on propane use by any means it seems like a 100 lb cylinder will not adequately supply a genny-ultimately you have to be able to vaporize enough fuel quick enough or you will "run out of gas" even with propane in the tank.

Allowing the system to run only one pump should be simple enough-simply use an ice cube relay across utility power to disable a second pump.

The comments on starting a pump are correct-a typical motor can require 2 to 3 times the full load amps at start up.  It would be wise to verify that the genny you are wanting to install has the peak capacity to handle the pump start up-and if you decide to run both, you need to add that peak capacity to the running amps of one of the pumps.  An electrician should be able to tell the actual start up amps=but that can be affected by the actual generator output voltage.

Not sure what an ice cube relay is but my concern would be that the controls want pump #1 to run but only pump #2 is on the genny and power goes out.




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[Stephen Swaffer]

Sounds like Don has things under control-I have worked with similar systems-though I obviously don't know his exact system.  To me, the easiest would be to power the whole "water plant" and let the control system work as normal (I am assuming that loads other than the pumps are minimal).  An "ice cube" relay is just a small control relay.  The control obviously has a way to determine that one pump is falling behind, so "lets start the second one"-should be a simple matter to interrupt that call for "more horsepower" when there  is no power at the utility terminals.

Cost of relay $15 give or take, a decent controls electrician under an hour to wire it in.

[don mcmeckan]

Sounds like Don has things under control-I have worked with similar systems-though I obviously don't know his exact system.  To me, the easiest would be to power the whole "water plant" and let the control system work as normal (I am assuming that loads other than the pumps are minimal).  An "ice cube" relay is just a small control relay.  The control obviously has a way to determine that one pump is falling behind, so "lets start the second one"-should be a simple matter to interrupt that call for "more horsepower" when there  is no power at the utility terminals.

Cost of relay $15 give or take, a decent controls electrician under an hour to wire it in.

Hi Stephen, you're right, we are going to do a completely parallel system.
He'll set up a replica of the panel in the pumphouse, then do an automatic switch over.

Going to do more research on sizing the propane tank, the engine in a genny probably uses more fuel than for stove or barbecue!

The electrician looked over the system and said an 8000 watt unit will do the job just fine.

Thanks everybody for all the info!

By the way, to all the east coasters who are in the storm, better to over prepare than under prepare.

Any of you had to use your backup?

Thanks,       Don

[Rob Spence]

Hi Stephen, you're right, we are going to do a completely parallel system.
He'll set up a replica of the panel in the pumphouse, then do an automatic switch over.

Going to do more research on sizing the propane tank, the engine in a genny probably uses more fuel than for stove or barbecue!

The electrician looked over the system and said an 8000 watt unit will do the job just fine.

Thanks everybody for all the info!

By the way, to all the east coasters who are in the storm, better to over prepare than under prepare.

Any of you had to use your backup?

Thanks,       Don

No need for standby power for this storm though I had both my Bobcat loader and Kubota snowblower out this morning.



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