Boeriemore

I phoned the manufacturers today. Spoke to a technician. When I told him my old speed heats worked fine with the thin cable he said that their elements have been upgraded to SABS specs and they recommend 4mm2 cable, All he said is that the element requires this. I failed to ask him why, what effect would the thinner cable have, would it result in the element not heating up to its full potential? Anyway, I have just bought 4 mm2 cable so one speed heat will be up to spec. but last week I replaced a faulty 5kw unit with a new one and this one is connected to 2.5mm2 cable and I am not going to replace it as part of the cable crosses the yard and is encased in concrete.

My 5kw speed heats are rated at 22 amps. For 18 years I have had these speed heats connected to these cables with no problems. This is what causes my confusion.

Thank you Superdiy, I have tested and can confirm that the thin cables do not get hot. The water pressure micro switches activates the elements and it does take a while to get fairly hot but not so long as to be an inconvenience. Your advice means I will have to remove the existing cable, presently secured to the wall and drill a larger hole through the wall as well as connecting it to the DB.

Back to the need for 4 mm2 cable. Prestigo state that a 5 kw unit with a cable more than 4 meters "they recommend" 4mm2 cable. I already bought a length of 2.5mm2 cable now its wasted and I have to buy the thicker cable. However, I have checked the existing two 5 kw units on my property and they have been working for years with no problems and both have cables over 10 meters in length YET the one has 2.5mm2 cable and the thickness of the other is less than the thickness of the 2.5mm2 cable. So is there really a need to upgrade the cable????

Thank you Superdiy, As a relative layman, I feel that the most likely culprit would be item 3.

In my cast the neutral wire may have touched the earth wire but nothing else except my fingers. Strange that this only happens on this particular speed heat. I have two others in the home and have never had this occur while working on the wiring from them.

Somewhat off the topic but here it is. Connecting or disconnecting the unit's wires I obviously first switch off the circuit breaker but the home's earth leakage switch trips every time.

Thank you for that helpful table. So I wasn't far out with my calculation.

If my calculations are correct then 4 mm2 equates to approx. 2.25 mm diameter. Would that be correct?

A belated update. I bought two 5kw units and one 3.5 kw unit for a shower. Bought what was called 2.5 mm 3 core cabtyre for this unit.. I installed them all but the problem is that the cold winter water does not heat up enough for a warm shower. I now intend to swap by fitting this unit by the kitchen sink and the 5kw unit in the shower. The information sheet states that should the distance between the 5kw unit and the power source be more than 4 meters then they recommend a 4mm2 cable. Same confusion. Is the thickness of each of the three core copper wire 4 mm in diameter which would make the total cable diameter huge?.

Prestigo's web site stipulates that their 5.0 kw unit requires to be connected to a 35 amp breaker but the 3.5 kw unit can connect to a wall socket. Thank you for your input. Edit: Checking online tables and a wire size calculator I get conflicting answers. The calculator worked out 16 AWG, one table 10 AWG and another 8 AWG (based on 25-30 feet length)

The cable needs to be 8 meters in length and will be plugged into a wall socket. So is 2.5 mm the diameter of each wire?

The info pamphlet states that this unit draws about 15 amps and requires a minimum of 2.5 mm2 cable. I assume this refers to the cross section area of the cable with the three copper wires within. Surely the thickness of wire casings could vary so the individual wire diameter would be a better and safer way of establishing what is required? Help here would be most welcome.

I have always had one in my shower and one for a kitchen sink. The shower unit is now giving problems. I showered last night and using a thermometer I determined that 30 degrees was the max. temp. slowing down the flow resulted in the element switching off. There is probably a switch / thermostat that is faulty. I doubt that this part is replaceable.

I have some info on Prestigo's Speed heat. The 3.5kw unit can be plugged into a wall socket and 20 degree water can be increased to 49 degrees max. The 5.0kw unit must be connected to a 25 amp breaker and 20 degree water can be increased to 59 degrees max. Food for thought.