Does armoured cable / Garage CU use extra energy?

Hi,

I've been monitoring my energy usage using a TREC CurrentCost monitor and a seperate plug-in monitor and found something strange when I use a electrical item in my garage...

If I switch on a 9v PSU adapter, the plug-in monitor shows it's energy usage as 1 watt (as expected). The TREC monitor however shows 30 Watts usage through the electric meter! - (With nothing else but the TREC and the PSU switched on. The TREC on it's own doesn't register any usage.)

The TREC and plug-in monitor measurments corospond with each other when checking several items inside the house i.e. If an appliance shows 60w on the plug-in monitor, the TREC shows 60w.

My garage is linked to my house from the back of a double socket on the house, along circa 7-8metres of armoured cable into a garage GE consumer unit. Wiring is original as fitted by the house builder circa 15 yrs ago. The PSU is for a FM receiver unit (to operate a door opener) and is currently switched on 24/7 using 30watts instead of 1w

Is it 'normal' for armoured cable / a 2nd consumer unit to require an additional 30watts of energy??? If not, any idea's on what's causing the increase in usage?

The PSU's cables are attached to the wall so before I start removing it and trying it in the house, I thought I'd ask on here!?

UpgradeMe

P.s. My next test (when I have the house to myself) is to try some other item (perhaps a 60w light) and compare.

It should not use any power connecting a garage and the PSU should use the same where ever it is plugged in.

I did have a similar problem on the Falklands where there seemed to be 200kW more being generated than used.

Lucky it snowed in the night and one patch melted first. Digging where snow melted I found a bad cable joint. In fact plumbers denso tape not proper joint.

So may be there is a fault in your cable. However likely you will not get any snow now so you will have to do it the hard way.

ericmark said:

Lucky it snowed in the night and one patch melted first. Digging where snow melted I found a bad cable joint. In fact plumbers denso tape not proper joint.

So may be there is a fault in your cable. However likely you will not get any snow now so you will have to do it the hard way.

Click to expand...

Thanks eric for the tip!!

Part of my 7-8m of armoured cable is underground (c2m) the rest is exposed on the brickwork inside the garage or outside of house. There 'should' be only three joints (Back of socket inside house, Consumer unit, socket in garage), if one of these is bad, could that cause it?

It's fairly easy for me to visually inspect them, the underground bit is more of a problem as it's paved. Is there any test I could conduct with a multimeter on the cables?

UpgradeMe

It's likely that the TREC device is not capable of registering very small loads accurately, since to do so would make the device prohibitively expensive. It can only be an estimate anyway, as these things only measure current, and assume the voltage is fixed.

The plug-in adaptor is probably more accurate for small loads, since it has a direct electrical connection, wheras the TREC is simply a clip around the incoming supply wire.

A better test would be to switch on some fixed load of a few hundred watts, and see what adding the PSU in the garage makes to that reading.

flameport said:

It's likely that the TREC device is not capable of registering very small loads accurately, since to do so would make the device prohibitively expensive. It can only be an estimate anyway, as these things only measure current, and assume the voltage is fixed.

Click to expand...

If I switch on a 1watt appliance inside the house, both the TREC and the plug-in monitor show the same figures. i.e. they both register 1w of usage.

flameport said:

The plug-in adaptor is probably more accurate for small loads, since it has a direct electrical connection, wheras the TREC is simply a clip around the incoming supply wire.

Click to expand...

Yep, the plug-in will show <1w whereas the TREC will only register 1w or greater.

flameport said:

A better test would be to switch on some fixed load of a few hundred watts, and see what adding the PSU in the garage makes to that reading.

Click to expand...

I'll try it with a light bulb (I have a 60w lamp I could use) and see what happens on it's own, and then when I switch on the PSU as well when I get the house to myself!

UpgradeMe