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Whole House Standby Generator

Bob Jackson
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by Bob Jackson

After several near misses by hurricanes and listening to the experiences of people who had no power for days or weeks, I decided to install a Guardian 30,000 Watt standby electric generator that runs on propane or natural gas to power the entire house.

Choosing a Whole House Generator

I considered a less expensive portable gasoline generator but dropped the idea because portables are very loud, require large amounts fuel (who wants to haul and store 50 gallons of gasoline to keep it running for a week?) and is too small to power the electrical appliances I want to use – especially the central air conditioner.

The factors in my decision making were:

  1. A mold deductible of $50,000 in my homeowners insurance policy. Mold damage happens quickly with no air conditioning and high humidity in Florida
  2. The probability that power would be out for days or weeks after a hurricane
  3. A standby generator would provide electricity for power tools to make emergency roof repairs
  4. Power for the well pump for water
  5. Comfort

A whole house generator met my requirements:

Guardian 30KW Standby Generator

Whole House Generator Cost

After extensive research, I decided to buy a Guardian generator. My final costs were:

  • $9,055 generator and automatic transfer switch
  • $2,600 electrician services (2.5 days of work)
  • $2,700 for the gas company to bury a 500 gallon LP gas tank, gas hookup and fuel
  • $160 for 32 bags of cement mix
  • $55 for electric cement mixer rental
  • $200 for landscaping rock and stone curbing
    $14,770 total installed

I framed and poured the 4ft x 7ft x 8in concrete pad, placed the generator on the pad and installed 3/8 inch anchor bolts myself.

Generator Capacity Sizing

One method of sizing a whole house standby generator is to add up the loads for all the electrical appliances you want to run simultaneously. Note that there are two types of loads: resistive loads such as lights, ovens and TV; and inductive loads (things with motors) including the central air conditioning system, pool pump and well pump. Resistive loads are the stated value (e.g. 100 watts at 120 volts). Inductive loads will create momentary startup surges, drawing perhaps 150% more amps than the ‘steady run’ rating as printed on the motor.

The second method is to pick a generator large enough to operate the central air conditioning system – which was my #1 objective – with everything else turned off – and rotate services. e.g. Run the air conditioner for 1 hour, turn it off, and watch TV or run the Microwave and lights.

The surest way to determine your load requirements is to have an electrician place an amp meter on the mains and measure the actual load of the devices you want to operate. The peak load value is found by measuring the startup current draw when the air conditioner and other inductive loads are turned on.

The specifications for the Guardian Model 4988 generator I purchased are:

  • 30KW at 120 volts steady load, equals 250 amps
  • 45KW inductive load momentary surge
  • Ford V6 3.0L liquid cooled engine

As it turned out, this easily powered all of my house electrical needs (including the central air, pool and well pumps) with no special power management techniques.

Automatic Transfer Switch

An automatic transfer switch (ATS) contains electronics and a huge switch to that senses when the utility power is lost, automatically disconnects the utility mains and connects the generator inputs to the main circuit breaker distribution panel. I highly recommend an ATS it allows the generator to kick in without making trips outside to switch over to generator power.

Hiring an Electrician

Finding an reputable and honest electrician turned out to be challenge. The good ones were backlogged and would only do the job if I purchased the generator from them. (At the time, the housing market was still booming.) Several electricians were willing to do the job, but unwilling to provide a written and itemized fixed price proposal. More alarming was that several licensed electricians, including some listed on the Generac web site, said no building permit was required! I called the county building department to verify. The building dept. said a building permit is absolutely required and my homeowner’s insurance wouldn’t cover fires or damage from unpermitted work. Furthermore, I could be held responsible if my generator back fed electricity into the utility grid and electrocuted a lineman. I called Generac and provided the names of the ‘approved’ dealers/electricians who gave me this false and dangerous advice.

Eventually, I found an electrician that:

  • Was licensed and insured.
  • Had installed many of the Guardian generators.
  • Said a building permit is required without prompting for the correct answer.
  • Provided a written, itemized, fix price quote that included initial turn-up testing and customer hand-off procedures.

This particular electrician did an excellent job and handled follow-up warranty service directly with the factory.

Buried Propane Gas Tank

The local propane company was pleasure to work with. They buried a 500 gallon liquid propane tank, installed the gas underground lines, converted the carburetor from natural gas (factory default) to liquid propane and filled the propane tank.

I chose a 500 gallon propane tank as this was sufficient to operate the generator for about 10 to 15 days, depending how I managed my electrical demands. The generator spec. sheet states the cubic feet gas consumption at various operating loads, which I used to calculate the expected runtime for a given tank capacity.

Generator Installation

After checking prices with several local retailers, I found the best deal by ordering from Home Power Systems. The generator was dropped shipped from the Generac factory (owner of Guardian brand) and arrived on a tractor trailer. Home Power Systems and the truck driver called me a couple of days in advance to schedule the delivery.

The truck driver used a pallet jack to move the generator into the garage until the outside preparation were complete. The generator weighs about 1500 lbs. with the crate and fortunately my driveway was level with the street, so getting it inside was not a problem.

Concrete Pad

The generator sits on a concrete pad. I prepared a 4 foot by 7 foot by 8 inches deep pad using thirty two 60 lb bags of cement. I did this by digging 6 inches below grade with a shovel, leveling the base and framing the sides with 2×4 lumber. The top of the 2×4 frame is set 2 inches above grade for the final height of the pad. The 2×4 frame is held in place by wooden stakes around the exterior held in place with screws. I also laid a wire mesh in the concrete for extra strength. A portable electric concrete mixer rented from Home Depot made the mixing and pouring of concrete manageable. The concrete was finished using a hand towel and bull nose edger. Remember to call the kids so they can write their names in the corner, too! Overall, this was a good days work.

Placing the Generator on the Pad

The generator is big, bulky and heavy (1350 lbs). The pros use a forklift maneuver the generator onto the concrete pad. I didn’t have access to one, then I came up with an idea from the ancients. I rolled the generator into position on wood fence posts. With a couple of neighbors helping, we kept placing fence posts in front, pushed and moved the back post to the first position. It worked great! It helped that I had a very level yard so there was no danger of the generator running away.

Here’s the generator bolted down to the concrete pad. (The unit is level, only the camera is tilted.) Gas and electric hookup is next.

Propane gas hookup, manual shut off value, and pressure relief regulator. Duct tape covers the underground electrical conduit against the wall that was set into the concrete for a neater installation.

The gas company buried the propane tank in the yard and installed the gas line, shutoff valve, regulator and connected it to the generator. Notice the black rubber section of fuel line for a vibration isolator to minimize the chance of a fuel line connection working loose:

Whole House Generator - Gas Line Regulator and Shutoff Valve
Whole House Generator – Gas Line Regulator and Shutoff Valve

View of the generator gas line plumbing. The black rubber fuel hose vibration isolator is denoted by the yellow arrow. The generator is about 15 inches away from the house. My intention was to locate the generator 18 inches away from the house but I made a measurement error locating the J anchor bolts in the concrete pad when I was studying the generator drawings before the generator arrived. This made for a tight squeeze when servicing the generator. Next time I’d place the generator 3 feet from the house for comfortable maintenance access:

Generator and gas hookup view from the other side:

Whole House Generator on Concrete Pad
Whole House Generator on Concrete Pad

The gas company buried the white PVC regulator relief vent line to safely vent the propane gas around the corner of the house away from the generator and potential heat/spark sources. The regulator relief would activate only if there were an usual overpressure event:

Whole House Generator - Gas Regulator Relief Vent Line
Whole House Generator – Gas Regulator Relief Vent Line

Another view of the propane gas generator hookup. The red lines on the wall were for locating the generator electrical hookup, which is waiting for the electrician:

Whole House Generator - Gas Regulator Plumbing
Whole House Generator – Gas Regulator Plumbing

The Automatic Transfer Switch (ATS) was placed in the garage next to the main circuit breaker panel.
A = 200 amp Main Circuit Breaker Panel.

B = Automatic Transfer Switch

C = Utility power lines

D = Generator power lines

E = Generator control signal wiring conduit

The 500 gallon propane tank was buried for two reasons:

  1. So it couldn’t be damaged in a hurricane.
  2. An above ground silver tank is very ugly.

All you see above ground is the inspection hatch!

I’ve had the generator for over a year now and am very satisfied. The family has grown dependent on the generator, enjoying power during thunderstorms and other short term blackouts. Fortunately, no hurricanes… yet.

Bob Jackson

automatic transfer switchbuilding permitburied propane tankchoosing a generatorconcrete pad for generator
Bob Jackson
Bob Jackson
Technology product manager by day and a prolific handyman in the evenings and over the weekends. Bob was the founder of the original Handyman How To website and that tradition continues on this site with excellent new handyman content into the future.
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