Thread: Generators

I'm in the market for a generator.

Power demands will be fairly light:

a couple of computers
a couple of fans
half a dozen lights

It's only for the power cuts which we get now and again but which always seem to happen at the worse possible times.

Any suggestions on models/prices available? Roughly how long do they run for, i.e. how much gas per hour?

used the little Honda 1 kw portable sets for years - on my boat and around various site offices,
never had any problem whatsoever .
Mine used to run for about 2/3 hours on a tankful which I think was 1 gallon

Can leave it wired up with a changeover switch /isolater and a light bulb wired in on the Mains side of the changeover/isolater so that you can see when the mains comes back on .

Can linkup an auxhillary gas tank by getting an outboard motor tank with the delivery feeding through the genset filler cap this lets you top up the fuel without stopping the set (and is a lot safer than filling the tank of a hot set in the dark !!!)

You really need to add up all your power usage (of the stuff you want to run), multiply by 1.5 or so and then get the next bigger unit, particularly as you are expecting to run the fridge/freezer which will take a high start current.

Check out gensets at your local farm shop, we got a little Sakari 4kVA (local manufacture I believe) about 3 years ago, don't remember the price though, runs lights, fridge, fans, telly and a couple of PCs it also has electric start so the missus can get it going whilst I remain guarding the beer from the dog.

Whatever you get, don't get the bright idea of using a cable with a plug at both ends to connect it into your house. This is dangerous for the obvious reason (live prongs) and the less obvious possibility of back-feeding into the supply with it's attendant danger to the linemen attempting to restore your power plus you'll be supplying juice to the neighbours .

Either install a proper transfer switch or go for the simpler route of running a traily lead from the genset and plugging in all the stuff you need to run. We're in the process of converting our manual transfer to an automatic one with auto start of the genset, lazy sod that I am

Hell I got one that I want to sell,, half price too, 5KW, electric start, have built the switch with isolaror so it is safe to run the house with the gen with a power outage, [got 2 switches and only one can be on at a time] without killing some somchai up a pole. has only ran a few short times, mostly just to warm it up and power is rarely off anymore.

The framework under it is on wheels so it is easy to move around too.

Originally Posted by More Volts Igor

You really need to add up all your power usage (of the stuff you want to run), multiply by 1.5 or so and then get the next bigger unit, particularly as you are expecting to run the fridge/freezer which will take a high start current.

Check out gensets at your local farm shop, we got a little Sakari 4kVA (local manufacture I believe) about 3 years ago, don't remember the price though, runs lights, fridge, fans, telly and a couple of PCs it also has electric start so the missus can get it going whilst I remain guarding the beer from the dog.

Whatever you get, don't get the bright idea of using a cable with a plug at both ends to connect it into your house. This is dangerous for the obvious reason (live prongs) and the less obvious possibility of back-feeding into the supply with it's attendant danger to the linemen attempting to restore your power plus you'll be supplying juice to the neighbours .

Either install a proper transfer switch or go for the simpler route of running a traily lead from the genset and plugging in all the stuff you need to run. We're in the process of converting our manual transfer to an automatic one with auto start of the genset, lazy sod that I am

Igor has some bloody good advice & should not be ignored.

Also, what he says about "back-feeding" into the supply, is about an incredibly dangerous situation, which most people do not understand. Generally speaking, supplying a domestic residence, which is connected to the main power grid, with internal generated power is only done by electricians. This should not be a DIY project unless you are a qualified electrician.

With regard to generator sizing, I have prepared an example of generator sizing (for single phase 220 volts) as follows;

Continuous Load calculation.
4 x 60 Watt incandescent lights - - - - - - - - - - 240W divided by 220 = 1 Amp.
1 x 300 Watt fridge - - - - - - - - - - - - - - - - - - - 300W divided by (220 x 0.8) = 1.7 Amps.
1 x 300 Watt freezer - - - - - - - - - - - - - - - - - - 300W divided by (220 x 0.8) = 1.7 Amps.
1 x 300 Watt TV - - - - - - - - - - - - - - - - - - - - - 300W divided by 220 = 1.4 Amps.
1 x 100W "printer" fax/phone - - - - - - - - - - - - 100 divided by 220 = 0.5 Amps.

Total continuous Watts as listed - 1240 Watts.
Total continuous current as calculated - approx 6.3 Amps.

Surge Load calculation.
The only items that will have a surge current are the fridge, freezer & TV.

1 x 300 Watt fridge - - - - - - - - - 1.7 Amps x 4 = 6.8 Amps.
Fridge surge - - - - - - - - - - - - - - 6.8 Amps - 1.7 Amps = 5.1 Amps.

1 x 300 Watt freezer - - - - - - - - 1.7 Amps x 4 = 6.8 Amps.
Freezer surge - - - - - - - - - - - - - 6.8 Amps - 1.7 Amps = 5.1 Amps.

1 x 300 Watt TV - - - - - - - - - - - TV surge is approx 1 Amp or less.

Total surge current - 10.3 Amps.

Your generator will need to supply a continuous current of 6.3 Amps.
Your generator will need to supply a total surge current of 6.3 Amps + 10.3 Amps = 16.6 Amps.
Converting these figures to "Apparent Power" (VA);
16.6 Amps x 220v = 3 652VA surge.
6.3 Amps x 220v = 1 386VA continuous.

Since you will not find a generator with these exact "continuous" & "surge" ratings, you must buy a generator that can accommodate the surge rating. ie you will need a generator with a surge rating of no less than 3700VA for the above situation.

Also, most "portable" generators have a duty cycle, whereby it can only operate at full load for a maximum period of time. If this operation time is exceeded, the life of the generator can be dramatically reduced. Generally, reduced loads mean a longer operating life.

Unless your "portable" generator has inverter technology, it may produce a waveform that can be detrimental to certain equipment.

In your situation, "standby" generators are used because they are designed to operate continuously & they also provide a "clean" output waveform (without the use of electronics).

An "inverter battery" arrangement is a good idea, particularly if your supply is "regular" about the times at which it fails & for "how long" it fails. The only thing about this arrangement is that it cannot be designed by just anybody. If you wish to get your moneys worth, be prepared to spend the correct amount of money. As with generators, "pay peanuts, get monkeys".


EDIT.
"Young Frankenstein" is one of my favourite films. Marty Feldman: "Bluker!". <horses whinney & neigh loudly>

Originally Posted by Happyman

Can linkup an auxhillary gas tank by getting an outboard motor tank with the delivery feeding through the genset filler cap this lets you top up the fuel without stopping the set (and is a lot safer than filling the tank of a hot set in the dark !!!)

This is partly true we did something very similar on our racing rig to provide constant fuel feed without dangerous filling next to a hot exhaust pipe, for when we had night work or night races.. The problem with this idea is that the fumes are the most explosive part, even more so than actual fluid so leaving the cap open is really not advisable..The exhaust gets white hot..

What we did to avoid this is just add the male side of a marine quick disconnect to the fuel line on the generator by cutting it and adding a small brass 'T' in-line with a brass valve to control fuel direction and a tail of fuel line. Once the fuel in the tank ran out we just hooked up the boat tank with the female end of the fuel line just like changing tanks in a boat and switched the valve over to the boat tank and pumped it up like in an outboard. No leakage, completely safe and no need to open anything, re-fill anything around hot exhaust, and the tank size gives you much more run-time say through the night if necessary, and you can have a couple of them with the additional length of lead you can add you can also move the tank away from the generator all together, to a safe distance but not too far..

Most marine stores here carry all of these pieces that I've seen..