Why can't you run two MH bulbs off one ballast

[Bob I]

Originally Posted by StirCrazy

well it all comes down to the bulb design, MH bulbs have no current limiting device in them whats so ever so as they warm up there resistance will drop causing them to accept more power. so running a 175 off a 400 watt will probably result in a melt down at best. now as for running two 175 watt bulbs off one ballast there are a couple problems.

the first being as there is no current limiting device except for the ballast you have no way of insuring the power is split evenly between the two bulbs. in this situation which ever bulb heats up faster will draw more and more power which will cause it to heat up more and then draw more power (you can see where I am going).

the second problem is one ballast cannot supply enuf starting current for two bulbs.

all and all, I think this would be a dangerous thing to try.

Steve

Although the explanation is not fully correct, as resistance rises with temperature increase, I will not try my explanation. It is best left alone. If you do not have a supply of free bulbs, don't even think about it.