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Old 07-19-2002, 07:21 AM
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Mark Wilson Mark Wilson is offline
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so it sounds like you have what is called a "series/parallel" network. your transformer outputs 60 volts, you elements require a 15 volt drop, so you hook 4 elements in series, on several parallel legs of your circuit.

if this is the case, then what i said the first time is still true. if you put all of your elements in series rather than in series/parallel, you end up with the same control scr, the same elements, the same number of elements, you just loose the transformer.

lets discuss another example. 16 heaters, 4 parallel circuits of 4 elements, each requiring 15 volt drop at 200 amps, so that your total current draw for the furnace is 200 amps at 240 volts. the transformer outputs 60 volts at 800 amps, so that you have 200 amps available for each of the 4 parallel legs of the circuit. therefore each heater operates at 15 volts at 200 amps or 3000 watts. so since there are 16 heaters, you get 48,000 watts of heating. there is a 200 amp 240 volt scr in the primary of the transformer.

you can connect all 16 elements in series with the same 200 amp 240 volt scr, and get the same results without the transformer. you end up using the exact same number of elements, the exact same elements, the exact same scr, you just don't require the transformer.

if you hook 16 elements in series each with a 15 volt drop, you get 16x15 or 240 volts drop with 200 amps passing through all of the elements which the 200 amp scr controls.

of course you don't get something for nothing. you loose the transformer, but you end up with a less fault tolerant system in that if one element goes down, they all go down. but with a current monitor and given the reilability of the moly-d elements, maybe it is workable.

i am not saying that this is the best way to hook up your furnaces, i was just tring to understand the options, and find out if someone has done it before.
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