Delta and Wye Elements wired in parallel

[bramdam]

I manufacture heating elements and a customer wired a delta heater in parallel with a wye heater. They claim that this lowers the overall resistance of the delta thus causing this element to draw more amps than what it was designed for. I disagree and do not see how the heater is eternally wired would make any difference and that each element will draw the appropriate amperage. Line current into the delta heater will be higher than the actual phase current in the heater itself but combining the two types of configurations in parallel should not cause a problem. I am just looking for some re-assurance.

Thanks.

 

[Windadct]

Based on your general description I have to agree with you, especially since both elements are restive. Best bet ( as with almost every case) make a diagram for discussion.

 

[bramdam]

I will try and dig up the schematic. I do not know the parameters of the wye heater, only the delta heater. But here is the email for which I do not agree. I do believe we undersized a power cable thus leading to the start of all this for we did not account for the line amperage being higher than our phase amperage. I will work on a diagram of some sort.Dave,

This is the problem... When you wire "Delta" and "Y" heat bands in parallel, the delta heat bands show less circuit resistance and the total circuit resistance will decrease causing an increase in total circuit amperage. In-fact, most of the current flow will divert to only the delta heat bands and there will be an imbalance in power distribution between all the heat bands. It is improper to wire delta and Y resistive circuits together in parallel. Please feel free to review this with an electrical engineer from your supplier. We need for you to send new (12 awg) cable assemblies for each of the heating bands that was on the order. I will be at the customer's site on April 7th, and I can exchange all of the cables on your heat bands at that time. This way, we are sure that all of them will be ok when they are wired into the system. With 12 awg wire cables, there shouldn't be any issues going forward (whether they are wired "Y", "delta", or parallel Y/Delta). This would be the fastest and easiest solution.

 

[Windadct]

Wait - are you using the same heater elements in each leg? eg. You have a Delta with Element type A and Wye with Element type A? -- then the Delta will draw more than the Wye - but connecting the Wye will not cause the Delta to draw more than the Delta by itself ( there is no "diverting"). Ether way -- the two in parallel will draw more than ether one...the info above is still not entirely clear.

 

[sophiecentaur]

Best bet ( as with almost every case) make a diagram for discussion.

Absolutely. You can draw no conclusions about a circuit until you actually draw it out and specify the resistances involved.
Calculate the voltages across the resistors in the two cases and then what will the resulting currents and power dissipation be?

 

[NascentOxygen]

I manufacture heating elements and a customer wired a delta heater in parallel with a wye heater.

Comparing the Y with the Δ were their individual elements rated differently for voltage, in accord with the respective configuration?