Gentlemen, The man has a pole TX 200 yards away. Where is he? Out in the sticks! So many of these comments are not entirely relevant are they? The pole TX may only be 11 kV to 230 and 50 kVA. Regulation 5%, ignoring any volt drop issues!

The problem with the oven is simply its control system, and here the defect is obvious too, the "temperature" input has zero hysteresis and the control is "0n-off". Whoever designed this is obviously incompetent! For an oven, heat loss is quite slow in response to temperature, so a half degree of hysteresis would be much better than any mechanical thermostat and perfectly adequate, one or two degrees similarly if necessary. A system with very high sensitivity to a variable (in this case temperature) and instant full scale response feedback is basically unstable and will show all these defects as described. The best system would be one with proportional feedback with the elements controlled by a PWM IGBT or thyristor power control (pretty cheap), which would be more accurate and not pulse the mains power level!

I would return the item as unfit for sale, they cannot fix it because the DESIGN is defective!

David CEng etc.

Gentlemen, The man has a pole TX 200 yards away. Where is he? Out in the sticks! So many of these comments are not entirely relevant are they? The pole TX may only be 11 kV to 230 and 50 kVA. Regulation 5%, ignoring any volt drop issues!

The problem with the oven is simply its control system, and here the defect is obvious too, the "temperature" input has zero hysteresis and the control is "0n-off". Whoever designed this is obviously incompetent! For an oven, heat loss is quite slow in response to temperature, so a half degree of hysteresis would be much better than any mechanical thermostat and perfectly adequate, one or two degrees similarly if necessary. A system with very high sensitivity to a variable (in this case temperature) and instant full scale response feedback is basically unstable and will show all these defects as described. The best system would be one with proportional feedback with the elements controlled by a PWM IGBT or thyristor power control (pretty cheap), which would be more accurate and not pulse the mains power level!

I would return the item as unfit for sale, they cannot fix it because the DESIGN is defective!

David CEng etc.

Hi David

Is it a pole TX?  I asked last night, but as yet no reply either way.

I was trying to establish visually whether 3-phase was available. 

Around here (n Wales) besides single phase pole TX connected across two of the three phase 11 kV overhead lines, there are also 2-wire 11 kV overheads, which obviously would have a much, much greater cost to upgrade.

There is also 230-0-230 split phase, to consider, but I doubt whether this would help in this case.

Clive

Hi -I live in a rural area North Wales. It is an 11kv /440v TX supplying three properties but the Board only ran one phase to my property.

I have told LINCAT the catering equip supplier- It is not fit for purpose. for many of its faults and have a case pending against them in the County Court in Wrexham.- Do any of you have the regulation that I can quote on the --Violently Oscillating Current.-- And produce in court, as evidence of  defective design..

  Any Engineer will know the abuse my incomer is experiencing. 50 starts per hour with no ramp up s appalling. I will not even run it on my genset.

Hi Clive Sorry -I have been off this for a few days due to hunting down a gremlin on the hot water controls I have motor valves scattered hither and yon    with a N to E fault.  always a ***.-------I am up on the Horseshoe Pass Llangollen. It is a 3 wire 11kv line and a 50kva TX 440v -240v  serving three properties. The board only ran a single phase 50kva MD line to the place way back.

Anthony Dicker said:

I have told LINCAT the catering equip supplier- It is not fit for purpose. for many of its faults and have a case pending against them in the County Court in Wrexham.- Do any of you have the regulation that I can quote on the --Violently Oscillating Current.-- And produce in court, as evidence of  defective design.

Good luck! I suspect that they may try to argue that your supply is inadequate.

Have you asked SP Energy Systems for a quote for 3-phase?  A friend in Mold had a single phase overhead supply upgraded to 3-phase underground for around £8K. he dug the cable trench himself (he has a digger) about 120 metres.

Clive

You need to say that is should have been tested to EN 61000 3 3 .
Unless the makers instructions say otherwise,  a customer should expect it to meet this standard on any normal single phase supply.

If it needs a supply with an unusually low resistance or high current capacity to meet this standard, (which is set in terms of number of permissible voltage drop events per unit time.) then they were remiss in not warning you that a supply of remarkably low impedance is needed, over and above the basic third of an ohm or whatever you might reasonably think was adequate for a 50A load.

EN 61000 3 3 is the spec for flickers that 'CE marked' kit should meet - it is set in terms of a fractional voltage drop events over time so depends on both the load step and the supply resistance and the more violent events are only permitted much less frequently.

If the oven is CE marked, they should have either test results or be able to show by analysis, that it meets this standard, if it is CE marked and no such evidence is available then they are not doing the CE marking properly, but if it is not CE marked then it is illegal to sell it as new equipment.

Mike

CE and UKCA are now identical in this example.

Hi Clive you are at the wrong end of the telescope. I am on a three phase OH line reticulation system 3 consumers. Single phase to my property. BUT why should I pay £1 to upgrade- because the oven people cannot keep the elements inrush and short cycle demand  under control.-- ie I was in West Africa- they were burning out 40hp motors at one per week. I found them stop starting the motors  DOL 50 times per hour. That was   killing the motors. I sorted that -and never had another burn out.

Thanks MIke the court will give me a date in the next few months. I will follow up on the above info.

I e mailed the manufacture with the readings, he said   "thats how they work"   so no expertise there then.