Author Topic: 4.5kva output  (Read 3280 times)

vegoil

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4.5kva output
« on: October 10, 2018, 10:59:42 PM »
what is the safe kw out put for a 4.5kva 230volt bkb generator on a Lister CS8/1 could I pull 4.2kw without doing damage? the power is being used into storage heaters and a immersion water heater on motors are used.

what would you say the maximim amps for the 4.5kva alternator as not to overload it?
« Last Edit: October 11, 2018, 12:02:02 AM by vegoil »

vegoil

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Re: 4.5kva output
« Reply #1 on: October 10, 2018, 11:57:49 PM »
all the power is to go into elements in storage heaters I have one at 3.4kw on its own and a (2.5kw + 1.7kw) together giving 4.2kw also (3kw immersion +0.850kw) heater together, I am planning to have 3 time clocks one for each 3.4kw ,4.2kw, 3.8kw

what would be the maximim amps so as not to over load it?
« Last Edit: October 11, 2018, 12:04:51 AM by vegoil »

BruceM

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Re: 4.5kva output
« Reply #2 on: October 11, 2018, 02:01:12 AM »
For a resistive load, VA is  the same as watts, so 4500/230= 19.5 amps
Just make sure the generator rating is a full load, continuous service and not some BS rating.

vegoil

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Re: 4.5kva output
« Reply #3 on: October 11, 2018, 04:49:16 PM »
thanks for the advice, its an old 1969 Lister CS 8/1 SOM with the original generator I have had the winding's tested and they are all good
I have tried to attach a photo (no go)

Cheers John

ajaffa1

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Re: 4.5kva output
« Reply #4 on: October 12, 2018, 11:17:13 AM »
+1 Glort, old generators are rated for continuous output unlike the cheap Chinese crap they sell now. If it says 4.5 KVA that`s what you can run off it all day. The higher the load the more fuel you will burn but diesel engines need to be run hard or you get problems with cylinder glazing and carbon build up. Always good to fit a volt meter into the circuit so you can see how it is coping with the load, If you turn on a heavy load the voltage should drop a bit until the engine governor compensates by delivering more fuel. the voltage should then climb back towards nominal. Heavy loads tend to heat up the wiring a bit so there is usually a small voltage drop over about the first ten minutes until things reach a happy equilibrium.

If you are going down the route of timer relays, please use these to trigger proper power relays to distribute the AC current. The cheap Chinese timer relays are supposed to be rated at 20 Amps, I have had two fail in the last 18 months. One of them caught fire and could have burned my house down. I would recommend motor starter relays.

Bob

Bob

vegoil

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Re: 4.5kva output
« Reply #5 on: October 12, 2018, 03:45:31 PM »
I was going to use multiple 30 amp (Chinese) relays. the largest switching load per heater would be 15 amp I thought that I would give it a 50% margin, what do you think?

I have a amp,volt,and Hz meter fitted

Cheers

John

vegoil

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Re: 4.5kva output
« Reply #6 on: October 12, 2018, 05:04:21 PM »
this is the relay on ebay that I Got? 250VAC 30A High Current Contactor Relay Switch 12V DC Board Module Powered Shunt

Is this the same one that gave bother?

 I have a photo but cant seem to get it posted here or any other photos for that mater.

« Last Edit: October 12, 2018, 06:18:27 PM by vegoil »

listeroil

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Re: 4.5kva output
« Reply #7 on: February 02, 2019, 06:26:12 PM »
The 8/1 engined Startomatics with the 4.5kw BKB generator are rated for continuous use at 4.5kw.  However they are rated to BS1958 which states that the generator can be run at 10% overload for a period 1 hour in a 12 hour period. This is also true of the engine. They both conform to BS1958 spec. I do have a Lister brochure which gives this information but at the present moment it is buried under a massive pile, when I find it I will post a picture.

Mick

BruceM

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Re: 4.5kva output
« Reply #8 on: February 02, 2019, 07:22:17 PM »
A true 4.5KW is generous for most homes.  That's like a 6-8KW modern screamer genset.
Lovely machine!

listeroil

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Re: 4.5kva output
« Reply #9 on: February 03, 2019, 09:38:15 PM »
Just to be pedantic, although it does make a difference in this case, Both 4,5 KVA and 4.5 KW have been quoted for the same machine here.

You make a good point so I checked up my Lister manual and brochure for this particular unit and in all the publications it states 4.5KW.  Then I went and checked the brass spec plate on the actual BKB generator and it says 4.5 KVA.  I have now checked a few more Lister manuals and some of them say:-
8/1----4.5 KW----4.5KVA----230V----50CYCLES.     
All very confusing Listers seem to reckon KW and KVA are the same when in fact they are not the same. However IMHO KWs is what Lister advertise in there brochures and manuals and they would not state 4.5KW if it couldn't do that.  So I reckon this generator could easily handle the OPs 4.2KW.


oldgoat

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Re: 4.5kva output
« Reply #10 on: February 04, 2019, 10:31:52 AM »
All you pedants have forgotten to include the powerfactor which is usually stamped on the name plate that decides whether it is 4.5Kw or 4.5Kva

listeroil

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Re: 4.5kva output
« Reply #11 on: February 04, 2019, 07:44:25 PM »
It says PF .1 so does that make KW and KVA the same?

Mick
« Last Edit: February 04, 2019, 08:09:24 PM by listeroil »

listeroil

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Re: 4.5kva output
« Reply #12 on: February 05, 2019, 11:56:26 PM »
Heres a picture

BruceM

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Re: 4.5kva output
« Reply #13 on: February 06, 2019, 02:26:57 AM »
VA and watts the same at a PF of 1, which is what it's rated for, not 0.1. 

For linear loads like resistive heaters and such, Watts and VA are the same.  Only when using shitty switching power supplies and lots of crappy low PF light bulbs will you see a big difference, though induction motors aren't so hot sometimes either and could use some more capacitance in parallel to reduce the VA.  Simple enough, just monitor V and A and add caps to minimize the total V times A.  It's very worthwhile to reduce often run motor VA for inverters- they do draw real PV or battery power to generate every VA, real or reactive.  I've confirmed that with a design engineer at Magnum and also myself on my own inverter design.  For motor generators, bad PF loads only cost you 15% more in fuel, but mostly it just eats your total capacity and motor starting capacity. 

mike90045

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Re: 4.5kva output
« Reply #14 on: February 06, 2019, 07:01:52 AM »
And remember, that big old robust gear was built when a half gallon was 64 oz, not 60 oz like nowdays.