Midco Burner EC 200

Jim Pompetti

The burner is 2 years old, Found a bad transformer (120 /24vac) .When I replaced it I added a % amp fuse (In case the problem was not just the transformer). The system ran About 5 mins , and the fuse blew. I ohm everything all look good. Then I remover the T'stat from the circuit ,at the t'stat . It ran till it satisfied . So ,replaced the t'stst (Honeywell 4000) Got a call several hours later that the fuse went . Could the capacitor for the Fenwal control (high voltage for spark) cause a high amp draw to kill the fuse

tim smith

Re: fuse blowing

I would not think so but seen stranger. Odd that you change the stat and then it runs for much longer but still blows. Did you amp out the secondary circuit to see what it is drawing? You might be able to trace it down to the culprit drawing too much.  Tim

Jim Pompetti

Cheched

all,I'm thinking it blows at start up, sometimes. It only pulls 1.03 amp when running.      

LarryC

Fuses blow because of heat.

Fuses blow because of heat.  Internal heat from too much current.  Excessive external heat will cause the fuse to blow also.

 

Excess inrush current can be taken care by using a "Slo Blow" fuse.  If the fuse holder is making a poor contact with the fuse, that will also cause the fuse to blow.  Is the fuseholder getting "shined on" from a heat source?

 

Does the system use zone valves?  Could a defective switch be momentarily shorting out the 24 V supply?

The 5 Amp fuse should withstand a 100% overload for 60 minutes at room temperature before blowing.  I suspect that you have some sort of short circuit that occurs sometime during a heating cycle.

 

Larry C