peter5355

Is there a Formula for calculating household electrical items?

I was thinking of buying a generator but I need to know how much electricity all the appliances use so that I can get the right generator for the job.

I have all the manuals for each appliance which give how much power each appliance uses.

I do not know how much power a combie boiler uses if anybody knows that information can you please share that information with me.

Hero999

Just add up the power used (look at the manuals) by alll the appliances in your house.

Also, look at the current rating rather than just the power. Generators are normally specified in apparant power (VA) rather than power. Some loads will have a poor power factor, meaning they will draw a lot more current than you'd expect.

Short of going round with a meter and measuring the current consumption of everything, you're better off just estimating it if it isn't printed on the manual.

For example the combie boiler uses natural gas for the heating, it only uses electricity for the ignition and control circuitry so I'd allow for 50W at the most.

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peter5355

Thank you for your reply the information is very useful

ClydeCrashKop

You might check the Northern Lights or Westerbeke or Onan sites. They should have tables and formulas.
For reliability and a simple control circuit I recommend Westerbeke. Do not buy Onan.

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Papabravo

Let me ask you a question in return. Are the devices that you plug into a household socket in series or in parallel?

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Hero999

Surely that's a silly question?

The sockets are wired in parallel, therefore the devices are all connected in parallel.

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Marks256

If they were wired in a series, wouldn't you need more voltage? Then again, i know nothing about AC...

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peter5355

Do you know of any web sites that are in the UK that have these Tables and Formulas.

As I am with Scottish Power would they have that information.

peter5355

The Fuse Box have trip switches which are very sentive if you just touch an earth wire and it trips the device that it is connected too

Attached Images

Fuse Box.jpg (32.5 KB, 15 views)

Hero999

It sounds like you're talking about an RCD which cuts off the power when some of the current leaks to earth.

I was talking about series and parallel circuits.
http://www.berkeleypoint.com/learnin...l_circuit.html

All the devices in your house will be connected in parallel apart from a set of christmas tree lights.

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Hero999

That's a pretty silly thing to say, I don't think you thought it through.

AC works exactly the same as DC until you get tied up with the complecities of power factor.

If they were all wired in series the voltage would depend on what else you have connected and all the plugs would have to have something connected for anything to work.

Connecting loads in series done with a constant current supply, for example a LED lighting system might use one switching power supply which produces a constant current of 325mA - to increase the load you add more LEDs in series.

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Marks256

that is what happens when i get tired...

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I²R

Here in the US, we call those GFCIs (Ground Fault Circuit Interruptors). For those wondering what goes on inside these things, they work by passing both the hot and neutral lines through a differential current transformer. Normally, the current through the hot is equal in magnitude and opposite in polarity to the return current through the neutral; these two currents cancel each other out and the voltage across the secondary of the CT is zero. If there is an imbalance between the hot and neutral current, a voltage appears across the CT secondary. In the US, if the magnitude of this voltage represents a current differential of 5 mA or more, the GFCI trips. Contrary to what many believe, a GFCI does not need to be grounded in order to work properly. However, if no ground is connected, the cover plate of the GFCI and those of any (up to 6 are allowed per the NEC) protected downstream switches or receptacles must carry the label "NO EQUIPMENT GROUND."

Hero999

True but I think what people mean when they say that is that RCDs/GFCIs won't work on an IT system.

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rjvh

This is what i don't understand why do theý have so many diffrent names for the same device

i seen many building schematics and i came across 3 names

ELB (earth leakage breaker)
ELC (earth leakage contactor)
EFR (earth fault relais)

if you hear the full name it it's straight forward but if you but if you say to me RCD

so RCD stands for what??

Robert-Jan