FAQ

Standard eyePower PDU should not be used on a 110VAC supply. If this is required then please contact us to discuss a custom version subject to quantity required.

eyePower PDU are designed for EU mains or similar, 230VAC +/-10% with neutral and earth nominally at the same potential. Each channel has a single fuse which must be in the live path from supply to equipment. Balanced mains requires fusing in both live and neutral feeds.

An eyePower unit connected to any form of 230V nominal (eg 115+115 180 degree US style) will not suffer any damage or compromise safety. Fuse good and relay good measurements will be on the edge of working and may display a fault, although current measurement is unaffected, so if outlet current is still flowing (at the level expected) then you could assume fuse and relay are good in a control/monitoring system. Voltage measurement will lose its accuracy because frequency measurement is compromised.

We measure mains presence (yes/no) with 6M6 resistance into very reliable CMOS logic. That is 35 microamps (micro!) per circuit. The logic circuit is earthed, we have used this technique since the 1990s. It is valid, we use multiple 2M2 in series in case one fails short circuit, which it never will. Our 1990s units checked outlet live presence after individual relays only, but for eyePower we added a check after each fuse which is pre relay. This alerts you to a failed fuse on an output that isn’t switched on. So 14 fuse + 14 relay = 28 presence detects, about 1mA total live to earth.

To make that measurement live with respect to neutral rather than earth, we would need some logic at neutral potential  (requiring an extra isolated PSU that is neutral not earth referenced) then opto-isolate a multiplex of the “sniffs” into our earthed logic board.

We could use optos to neutral for every one of 28 circuits, put the price up and each would waste more energy than our 28 together.

Because the voltage measurements (shown on the graph) are also referenced to earth, total current to earth is about 1.5mA and well within the 3.5mA maximum allowed for a Class 1 appliance. It is unusual to have resistive leakage, it would normally be of no use whatsoever, leakage is normally capacitive for filters. Hence eyePower does conduct during a ‘PAT’ 500V insulation test which is not a fail. We have a note on PAT testing below. The analogy is measuring mains with a digital voltmeter, that too would fail a PAT 500V withstand test and require the alternative leakage test.

Sometimes we wonder whether we should offer a version that works on non TN mains. However, we offer single pole outlet fusing so this can’t be considered (UK regs) anything other than dangerous – to break an overloaded circuit where the unbroken leg may still be live with no way to isolate. For non TN mains, we would really have to remove channel fusing completely (like a US unit) but we always think outlet fusing is good to have with multiple 10A outlets on a 16A/20A supply, or offer two front panel fuses per outlet to cover the two legs as required by product standards. Then we have to wire individual outlet live and neutral from the front panel, rather than the existing rear neutral bus being one wire.

There is another reason we like our 1mA-ish of leakage that has been on thousands of units since 1999. From the BBC at Bush House to music studios in the Caribbean, from Israel to India, 1mA is enough to be sure that the earth is at least present, One 35 uA circuit will detect presence of dry string for earth, but 1mA works well. We have had countless calls over the years to say outlet LEDs are red and every time we can say there is no earth or L/N is reversed. In one foreign case, an entire building was missing its earth and we advised the user to disconnect all their technical equipment until resolved. Otherwise they could become the earth point for the entire building not under their control.

Typically known as Portable Appliance Testing (PAT) in the UK, electrical safety testing for Class 1 (earthed) equipment includes visual checks and measurement of protective earth conductor resistance. Insulation testing often follows, but where considered unsuitable this may be optionally substituted with the measurement of operational protective conductor (earth leakage) current.

Manufacturer guidance for electrical safety testing of eyePower PDU is to omit insulation testing because it is not suitable and perform the following tests:

1: Visual Test
2: Earth Bond Test
Test Value25A~
Pass0.20Ω
Duration5 seconds
3: Leakage Test
Test Value230V~
Pass1.50mA
Duration10 sec