Which generator type?

[cjc_td5]

I am after a generator to run some things in the house when we have a power outage (all too often) and to run a couple of pumps as part of my bushfire plan.

The house stuff would be mainly fridge and freezer, maybe a couple of lights if needed, a water pump (0.6kW) and the instantaneous gas hot water system so we can have some hot water.

The fire plan entails running a bore and additional pressure pump which draws about 2.6kW when both running. Both house and fire systems would not be run concurrently. When there is a fire, a cold fridge will be the last of my worries!

All of the above items contain electronic circuit boards of some description and so probably require a certain quality of power supplied to them?

I have been looking at a generator in the 4-5kVA continuous supply range (ie peak higher etc).

It appears that the two main types of generators out there are inverter or older capacitor types. The price difference at that size unit is quite huge ($4-5K vs $1-2K).

My questions are, can the above equipment be run off an older style capacitor style unit? Can I place a "power conditioning" device after the generator to "clean" the supply to vulnerable equipment? Or is an inverter generator my only real safe option?

I'm after a known brand generator (Honda, Yamaha motor etc), not a cheap Chinese copy.

Thanks

[Dorian]

Chris
Don't really have an answer for you directly, but some info around the problem.

Can you run your new style kit off the old style genset?. No one can give you a straight answer. The problem being is that the motors in the fridge/freezer/pump will be fine but the control boards can be a bit sensitive. Many of the control boards will run on 5Vdc (some 15Vdc etc).If the control boards have a good solid power supply circuit that uses large capacitors to drive the DC power supply then they should be fine with dirty power from the genset, if not then they might blow.

However if you are now getting brown outs and your normal supply is a single line in and earth return, this supply is probably testing the robustness of your appliances anyway.

Check your pumps for while they may only be X amps when running they usually take 2 or three times X to start, some a bit more.

A company called "Sola" make great power conditioning equipment, but as invertors have become cheaper they sell a lot less of these so they have become more expensive.

For your sensitive stuff you could use a capacitor type genset to charge a battery and run an invertor.

For your money you should look at going grid solar, you can get systems that will take a feed from batteries or another power source when you've got no mains supply or sun. You can then use the genset as the other power source or to charge the batteries. This will probably be more money but you will be getting a return on your investment everyday the sun is out and the invertor on the system will look after your apliances.

[Homestar]

Depends on your budget. Yes the inverters are more expensive, but they will run sensitive electronics better. Having said that, a standard cap excited unit will generally work fine as well. My inlaws regularly have blackouts and use an old cap excited 5KVA to run everything. The fridge, freezer, etc have never had issues. The electronics in these appliances are fairly robust and can happily run on anything from 220 to 260 odd volts, and between 48 to 52 Hz - which is what you'll get out of the cap unit.

Buy the best unit you can afford. Try to avoid cheaper imported units - parts are virtually un obtainable.

[cjc_td5]

Thanks Bacicat.
My main concern is the pumps as they draw a fair amount of current and also have pressure controllers etc which I presume may be sensitive to supply quality? The two pumps are Grundfos units so should be decent quality.

I am leaning towards a Gentech unit, say around 5kVA.

[Homestar]

Either will run the pumps fine. Grundfos are good units. A 0.6KW pump will draw a couple of amps when running, and paybe around 9 or 10 on startup, so a 5KVA will run a couple of these easily - even if they were to start together. The base load on you house (If it is a normal sort of size) will only be about 1KW anyway - with normal loads - lighting, fridge, freezer, etc. It will still leave you enough up your sleeve to run an AC, dishwasher, etc.

The inlaws never even bothered to turn off the spa (when they had one) and they never had any issues. The Gentech units are fine - if you were closer I could do you a good deal on one - a mate has 2 new old stock 6KVA Gentechs he bought at an auction that he is selling on.

[DeanoH]

................................The fire plan entails running a bore and additional pressure pump which draws about 2.6kW when both running..................................

Thanks

It seems to me that the biggest problem in dimensioning this system is in providing enough electrical 'grunt' to start the bore and additional pressure pump at the same time. If they use 2.6 Kw when running then I would have thought you'd need a minimum of 12-15 KVA to start them concurrently.
It may be possible to have some sort of 'soft start' option to decrease this initial load or it may be possible to have some sort of interlock so that both cannot start at the same time. Either/both options could mean that a smaller (and cheaper :)) generator could be used in this application.

Thinking outside the box here and assuming you have a submersible bore pump and a centrifugal pressure pump. What size tank/dam do you have at the bore ? Assuming a decent size might it be a lot easier/cheaper to plumb in a petrol driven pressure pump from this reservoir around the electric pressure pump with either a gate/ball valve or one way valve on its output ? Or if there is no suitable reservoir have a (smaller) generator to supply the submersible pump only with the petrol pressure pump as described above ? :)

Might sound a bit messy but could give the reqd. result a lot cheaper. :D


Deano :)

[pop058]

What about 2 Generators. One older larger for the grunt work and a newer smaller (eg Honda Eu 20i) for the sensitive stuff

just a thought

[Homestar]

Missed the 2.6KW bit. If I read that correctly, then you are talking about 2 pumps with a total running load of 2.6KW? If this is the case, then a 5KVA will still be fine as long as each pump is strated seperately, and not together. If both started together, the machine would grunt hard, but would just about get them away - flip of the coin depending on the genset and what the voltage drooped to.

If I was speccing a genset for a customer based on this info, then I would supply a 5KVA if pumps are started seperately, and an 8KVA if they were required to be started together.

Cheers.

[cjc_td5]

It seems to me that the biggest problem in dimensioning this system is in providing enough electrical 'grunt' to start the bore and additional pressure pump at the same time. If they use 2.6 Kw when running then I would have thought you'd need a minimum of 12-15 KVA to start them concurrently.
It may be possible to have some sort of 'soft start' option to decrease this initial load or it may be possible to have some sort of interlock so that both cannot start at the same time. Either/both options could mean that a smaller (and cheaper :)) generator could be used in this application.

Thinking outside the box here and assuming you have a submersible bore pump and a centrifugal pressure pump. What size tank/dam do you have at the bore ? Assuming a decent size might it be a lot easier/cheaper to plumb in a petrol driven pressure pump from this reservoir around the electric pressure pump with either a gate/ball valve or one way valve on its output ? Or if there is no suitable reservoir have a (smaller) generator to supply the submersible pump only with the petrol pressure pump as described above ? :)

Might sound a bit messy but could give the reqd. result a lot cheaper. :D


Deano :)

My retic system uses a submersible bore pump that feeds into a sand filter and then into a 2kl holding tank (2 IBCs), which a pressure pump then draws out of and feeds the retic and taps etc. In an emergency situation the bore can be routed directly to the retic & taps, bypassing the filter and pressure pump. This would result in iron staining if done for any period of time though. The pumps can easily be managed to start independently, ie not at the same time.

The existing system works at present as the bore and pressure pump flow rates are largely matched. This would be much harder with a petrol pump. I am also trying to double up on usage (ie generator being available for other uses), a petrol pump would just sit around taking up room when not needed.

I value your thoughts though.

Thanks,

[cjc_td5]

Missed the 2.6KW bit. If I read that correctly, then you are talking about 2 pumps with a total running load of 2.6KW? If this is the case, then a 5KVA will still be fine as long as each pump is strated seperately, and not together. If both started together, the machine would grunt hard, but would just about get them away - flip of the coin depending on the genset and what the voltage drooped to.

If I was speccing a genset for a customer based on this info, then I would supply a 5KVA if pumps are started seperately, and an 8KVA if they were required to be started together.

Cheers.

Yes the two pumps running sum to 2.6kW. The bore is approx. 1.7kW and the pressure pump approx. 0.8kW when running. I can manage them to start seperately. If a capacitor gen is on the cards, I can afford to go a bit bigger, up towards 6-8kVA.

Thanks.

[cjc_td5]

What about 2 Generators. One older larger for the grunt work and a newer smaller (eg Honda Eu 20i) for the sensitive stuff

just a thought

Good suggestion, but my major issue was driving the pumps which require a large current but also have some sensitive electronics in the pressure controllers etc. I wouldn't go charging phones off the generator, I would use an inverter off a battery or 12v off the car for this.

Cheers,

[slug_burner]

Poor power quality is most likely from small gensets. A bigger generator will not venture too far from a sine wave unless it is really overloaded which is unlikely as the protection cct will protect the generator. Switched loads could also cause you some problems, simple rotating machines will not chop up the supply to cause other sensitive loads a problem.