Underpowered electric power hose

tonic wine

Plug it in inside the house, it works fine.

Plug it in down the shed, it barely turns the motor.

230v at the socket. 2.5mm swa run from house to shed, ~25m.

Need bigger cable?

Any other ideas?

2011

tonic wine wrote: »

Plug it in inside the house, it works fine.

Plug it in down the shed, it barely turns the motor.

230v at the socket. 2.5mm swa run from house to shed, ~25m.

Need bigger cable?

Any other ideas?

This sounds like an issue with volt drop. from your post it seems that you have come to the same conclusion.

Remember when you measure voltage at the socket you should be doing this while the circuit is loaded i.e. when the power washer is running.

The volt drop is proportional to the current, so no current flowing will mean no volt drop.

Also the volt drop at the shed may only be part of the story. Have you an extension lead plugged into the shed socket?

When you say that the run is 25m to the shed, are you measuring from your main distribution board or for a socket that the shed is fed from??

What other loads are there in the shed that are fed from the same circuit??

tonic wine

2011 wrote: »

This sounds like an issue with volt drop. from your post it seems that you have come to the same conclusion.

Remember when you measure voltage at the socket you should be doing this while the circuit is loaded i.e. when the power washer is running.

The volt drop is proportional to the current, so no current flowing will mean no volt drop.

Also the volt drop at the shed may only be part of the story. Have you an extension lead plugged into the shed socket?

When you say that the run is 25m to the shed, are you measuring from your main distribution board or for a socket that the shed is fed from??

What other loads are there in the shed that are fed from the same circuit??

Thanks for your reply.

Volt drop is the problem. It drops to 150v plugged straight into a 16A 230V socket.. The power washer is 1.8kw
The cable is actually 4mm^2 swa. I thought this would have being sufficient.

Do you know what the formula is for working out cable selection and volt drop?
I could just run 6 or 10's, but I would like to input the 4mm into the formula to calculate the result.

Cheers.

freddyuk

http://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html

Try this?

M cebee

Something is wrong if shed is wired in 4sq and voltage is 150v
Maybe a problem with a connection or joint

tonic wine

freddyuk wrote: »

http://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html

Try this?

Excellent, thanks.

I entered the data, actually put in 100m as it not a direct route.
Only other loads on the cable are lighting circuits that were not in use at time.

It suggests 4mm^2 from the formula, which I thought would have being correct.

150v sounds like a massive volt drop?

tonic wine

M cebee wrote: »

Something is wrong if shed is wired in 4sq and voltage is 150v
Maybe a problem with a connection or joint

I'll look back through the route and connections.

It's joint in another shed where a supply was taken off for lights.

Bruthal

tonic wine wrote: »

I'll look back through the route and connections.

It's joint in another shed where a supply was taken off for lights.

Definitely must be a connection problem if all is ok in the house.

2011

As others have suggested, it sounds like there is a high resistance joint somewhere on the cable. If this is he case the joint will get hot when a current is drawn (I^2 x R). I suggest that you get this checked out ASAP as it my be a fire hazard.

If I were trying to find this problem i would measure the resistance of each section of the cable with a multimeter.

tonic wine

2011 wrote: »

If I were trying to find this problem i would measure the resistance of each section of the cable with a multimeter.

Would the resistance reading on the meter be notably higher at the problem joint?

Can I just take the readings from the connectors, or do I have to undo the connections before taking readings?

Thanks very much for the help.

2011

tonic wine wrote: »

Would the resistance reading on the meter be notably higher at the problem joint?

Yes. If the voltage at the shed really is 150V then the total volt drop is in the region of 80V.

As the power washer is 1.8 kW then the current drawn is approximately 8A.

The total resistance on the circuit = volt drop / current drawn = 80/8 = 8Ω (approx)

The resistance of 8Ω will be made up of all of the joints, the cable itself but most of it will be due to the problem joint. I would guess that the problem joint will be > 6Ω

EDIT: It would be good to actually measure the voltage at the shed.

2011

It would be interesting to know what the voltage is at the main distribution board is.

This may be as low as 220V meaning that the volt drop along the SWA would be less than we thought.

You are getting to the stage where IMHO it would be best to employ the services on a registered electrical contractor.

Bruthal

2011 wrote: »

Yes. If the voltage at the shed really is 150V then the total volt drop is in the region of 80V.

As the power washer is 1.8 kW then the current drawn is approximately 8A.

The total resistance on the circuit = volt drop / current drawn = 80/8 = 8Ω (approx)

The resistance of 8Ω will be made up of all of the joints, the cable itself but most of it will be due to the problem joint. I would guess that the problem joint will be > 6Ω

EDIT: It would be good to actually measure the voltage at the shed.

Measuring resisitances along a circuit is a bit impractical imo. With no loading it may not show up as expected.

If connector or junction box locations are easily enough accessible to do tests, then turn off the circuit and just redo the connections.

The washer will only be taking 4 or 5 amps if the voltage under its loading is down at 150v. Was the voltage tested under load in both shed and house?

If its 150v with no load using a digital meter, and is normal in the house, then the resistance of the fault will be in the mega ohm range, practically an open circuit.

2011

robbie7730 wrote: »

Measuring resisitances along a circuit is a bit impractical imo. With no loading it may not show up as expected.

Ohm meter, fly lead, simple.

If connector or junction box locations are easily enough accessible to do tests, then turn off the circuit and just redo the connections.

Easy to do if you know where the all of the connections are. There may be an unknown connection or damage to the cable.

Was the voltage tested under load in both shed and house?

I don't think so, that is why I suggested the OP get the voltage measured in both places in my last 2 posts.

tonic wine

just to clarify my readings on my dvm, i measured it at the 16A socket to be 233V under no load.
Under load at the 16A socket it was low as 150V.

I didn't measure at the main distrubution board, but the washer worked perfect there.

Bruthal

tonic wine wrote: »

just to clarify my readings on my dvm, i measured it at the 16A socket to be 233V under no load.
Under load at the 16A socket it was low as 150V.

I didn't measure at the main distrubution board, but the washer worked perfect there.

Did the pump in it ever get up to speed? The high starting current on motors will be sustained if they dont get up running to speed, which will cause the volt drop on long undersized cables.

A test you could do is try boiling a kettle in the same socket, if you can plug it in. And test the voltage during that.

2011

tonic wine wrote: »

just to clarify my readings on my dvm, i measured it at the 16A socket to be 233V

OK, if we go with the assumption that your test instrument is accurate you have at least 233VAC at your distribution board and the volt drop when the power washer is plugged in is 83VAC.

As Robbie says the power washer may not draw the full current when the volt drop is that excessive. This could be measured with a grip on ammeter.

Either way you have a volt drop issue by the looks of it. If this is a new problem it could be as a result of cable damage. All sorts of things can cause this, such as corrosion, rodents or an over enthusiastic gardner!

tonic wine

Should i be worried of a fire as lighting circuits are pretty much on all evening/night during the winter.

I thought the mcb would trip when the cables get hot?

robbie7730 wrote: »

Did the pump in it ever get up to speed? The high starting current on motors will be sustained if they dont get up running to speed, which will cause the volt drop on long undersized cables.

A test you could do is try boiling a kettle in the same socket, if you can plug it in. And test the voltage during that.

There must be a safety circuit built into the motor as it switches itself off when i close the lance on the power washer after a ~10 seconds, but it never got upto full speed and lacked power.
I'll try the kettle test. It worked a drill no problem to bore a few holes, but obviously that would have as much of a pull as a kettle.

2011 wrote: »

Either way you have a volt drop issue by the looks of it. If this is a new problem it could be as a result of cable damage. All sorts of things can cause this, such as corrosion, rodents or an over enthusiastic gardner!

It is a new problem, as it worked two years ago.
That is what really confuses me, especially if i can't find a loose connection somewhere.

2011

tonic wine wrote: »

Should i be worried of a fire as lighting circuits are pretty much on all evening/night during the winter.

Yes, this could be a fire hazard.

I thought the mcb would trip when the cables get hot?

A common misconception. The MCB will only trip if:
1) There is a short circuit conditions.
2) If the circuit is overloaded.

It will not operate just because the cable is overheating / going on fire.

It is a new problem, as it worked two years ago.
That is what really confuses me, especially if i can't find a loose connection somewhere.

It sounds like the cable had been damaged.

Bruthal

tonic wine wrote: »

There must be a safety circuit built into the motor as it switches itself off when i close the lance on the power washer after a ~10 seconds, but it never got upto full speed and lacked power.
I'll try the kettle test. It worked a drill no problem to bore a few holes, but obviously that would have as much of a pull as a kettle.
.

Yes the kettle on and volt test at it would be my first test. It will be a steady 2kw load, unlike the washer which if the motor is 1800 watt, could take 8 or 9kw+ at the instant of starting, and if the supply cables are inadequate, it will pull the voltage right down. It
probably takes less than these figures on starting, but still could be enough to pull the voltage down with a motor that cant get going.

This will cause the motor to be very sluggish to get running, and so prolong the high current its taking and in your case, trip out its overload device.

If the kettle also shows 150v, then look for connection problems. If its up toward 200v or more, then its likely the length/size of the cable run.

Is this washer something you newly tried in the shed, or it used to work ok?

tonic wine

robbie7730 wrote: »

Is this washer something you newly tried in the shed, or it used to work ok?

It worked two year ago in the shed.
thanks for all the advice.

Bruthal

tonic wine wrote: »

It worked two year ago in the shed.
thanks for all the advice.

If it did work properly, then a connection problem seems likely. Cable damage is a possibility alright, but it would be unusual enough to be damaged in such a way as to leave a volt drop problem, not impossible though. Where is the cable to the shed fed from?

tonic wine

robbie7730 wrote: »

Where is the cable to the shed fed from?

Another shed where the main distrubution board is.
the sheds have there own esb supply.

Bruthal

tonic wine wrote: »

Another shed where the main distrubution board is.
the sheds have there own esb supply.

A voltage test with the kettle anyway, or even better would be an electric heater of 2kw or so (it wont start boiling after a couple of minutes and go off), and do volt tests at the heater, at any junction boxes you know of, and where the cable connects to its supply end.

Everyone has their methods, but thats what I would do. Also when the load of heater or kettle is on, also test Live to Earth voltage at the shed with kettle in it, and see is it the same as Live - Neutral. If it happened to be a bad connection on the neutral, the Live to earth would still show 230v or whatever it is at the shed under load, indicating it is a connection problem with the neutral along the cable.

tonic wine

robbie7730 wrote: »

also test Live to Earth voltage at the shed with kettle in it, and see is it the same as Live - Neutral. If it happened to be a bad connection on the neutral, the Live to earth would still show 230v or whatever it is at the shed under load, indicating it is a connection problem with the neutral along the cable.

Good thinking, i should have checked that already.

Cheers.

M cebee

robbie7730 wrote: »

A voltage test with the kettle anyway, or even better would be an electric heater of 2kw or so (it wont start boiling after a couple of minutes and go off), and do volt tests at the heater, at any junction boxes you know of, and where the cable connects to its supply end.

Everyone has their methods, but thats what I would do. Also when the load of heater or kettle is on, also test Live to Earth voltage at the shed with kettle in it, and see is it the same as Live - Neutral. If it happened to be a bad connection on the neutral, the Live to earth would still show 230v or whatever it is at the shed under load, indicating it is a connection problem with the neutral along the cable.

i think the handiest tool(ideally) for this problem would be a 2-wire loop tester

you could take the L-N loop reading at various points ,live,no-load

i think i've seen regular loop testers in 2 -wire versions

http://docs-europe.electrocomponents.com/webdocs/0a0f/0900766b80a0f8bb.pdf

2011

tonic wine wrote: »

That is what really confuses me, especially if i can't find a loose connection somewhere.

Are you sure you checked all of the connections on the circuit ?

tonic wine

2011 wrote: »

Are you sure you checked all of the connections on the circuit ?

I haven't checked any as of yet.

I put it down to the cable wasnt big enough on the day until i entered the data into the cable selection formula that showed 4^2 is plenty big.

Connections will be looked at on monday, aswell as all other suggestions mentioned on this thread.

Bruthal

M cebee wrote: »

i think the handiest tool(ideally) for this problem would be a 2-wire loop tester

you could take the L-N loop reading at various points ,live,no-load

i think i've seen regular loop testers in 2 -wire versions

http://docs-europe.electrocomponents.com/webdocs/0a0f/0900766b80a0f8bb.pdf

It might show it, depends on the problem probably. Id find testing known points along the circuit with a voltmeter while the circuit is loaded would quickly tell what`s happening at that point.

The 1.8kw pressure washer would apply a fair heavier load than that if the motor is unable to get going. I assume the 1,8kw is the size of the pump motor.

M cebee

robbie7730 wrote: »

It might show it, depends on the problem probably. Id find testing known points along the circuit with a voltmeter while the circuit is loaded would quickly tell what`s happening at that point.

The 1.8kw pressure washer would apply a fair heavier load than that if the motor is unable to get going. I assume the 1,8kw is the size of the pump motor.

why wouldn't it show it


ya i suppose tracing back with a load on the end is handiest actually

Bruthal

M cebee wrote: »

why wouldn't it show it

If you had a shower for example, and its supply live wire was only touching the connection at the DB, it will show as fine through an ohm meter. The load of the shower however, will break down the connection, and wont work properly. So it might not show clearly with no load testing.

I think anyway:)