10+10=30???

[llldks]

On my 8v71ti I have block heaters which are on separate circuit breakers but share a common hot lead. When each block heater is on individually it draws about 10 amps but when they are both on they draw 30. Does that make sense?? Could this be due to them sharing the same hot lead?

Larry

 

[MikeP]

I suspect that the shared wire is undersized and, therefore, increasing resistance in the circuit when both are turned on. If the shared lead is easily accessible, turn both heaters on, wait a bit, and check to see if the common wire is warm.

 

[SEVEN]

I believe you hit it right on the head Mike.

 

[davidwigler]

On my 8v71ti I have block heaters which are on separate circuit breakers but share a common hot lead. When each block heater is on individually it draws about 10 amps but when they are both on they draw 30. Does that make sense?? Could this be due to them sharing the same hot lead?

Larry

I'm confused. If they have separate breakers how can they have common hot lead? The breaker feeds the hot lead.

 

[krush]

I suspect that the shared wire is undersized and, therefore, increasing resistance in the circuit when both are turned on.

Increased resistance means it will flow less current.

 

[llldks]

It looks like a hot lead from the main panel goes to a terminal of the starboard breaker and there is a short jumper lead to the port breaker. Sounds like I should run a separate hot lead from the main panel to the port breaker and eliminate the jumper lead.

 

[MikeP]

Increased resistance means it will flow less current.

Yes, K is absolutely right, per Mr Ohm.

But Larry, humor me and check that anyway; if any of the associated wiring is getting warm, the gauge is too small for the load. For that matter, the jumper wire you refer to, if I understand your description correctly, is totally incorrect for an elec circuit.

 

[davidwigler]

It looks like a hot lead from the main panel goes to a terminal of the starboard breaker and there is a short jumper lead to the port breaker. Sounds like I should run a separate hot lead from the main panel to the port breaker and eliminate the jumper lead.

If you have a sub-panel it should be served by one heavy gauge wire from the main panel. Maybe 6 or 8 gauge depending on total load and distance.

What you're calling the port and starboard breakers, are they in a panel? If so there should be a bus that feeds each breaker. If there was a need for a jumper wire you may have a broken bus. Some installers break a bus for an inverter. Why don't you post some pics?

Sounds like you found the problem.