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Old 07-18-2002, 03:18 PM
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Mark Wilson Mark Wilson is offline
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moly-d without the transformer

please excuse me if i have misunderstood the discussion here, so i would like to clairify a couple of points. it is my understanding that you need a step down transformer to take 240VAC down to 60VAC to run the moly-d heating elements with 4x the current available on the 240VAC line.

for example, if i feed 240VAC @60Amp into the primary of the transformer, i would get 60VAC @240Amp out of the transformer. if the output of the transformer was connected to 4 heater elements in parallel, each heater would draw 60VAC @60Amps or 3600 Watts. so for 4 elements, you could supply 14.4 KWatts of heat.

it is also my understanding that the normal method used in your furnaces has the heating elements in parallel, and that you use the scr's in the primary (high voltage side) of the transformer so that you don' have to buy bigger, more expensive high current scr's.

if this is true, then i have a question. if you connectecd 4 heating elements in series, not in parallel, you could still use the same scr's but you would not need a step down transformer. in the example stated above, you would have a 60 volt drop at 60 Amps on each heater so you would get the same total output power of 240VACx60Amps or 14.4 Kwatts, except without the cost of the transformer. i know that this is not the best configuration, as if one elements goes down, they all go down, until you repair or jumper around the bad element. but you still get to use the cheaper scr's and you don't need to buy the transformer. and if the moly-d heaters are as reliable as everyone says, then you don't need to worry about an element going down very often.

has anyone tried using moly-d heaters as i have described?

Last edited by Mark Wilson; 07-18-2002 at 03:22 PM.
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