Strange electrical problem - Fuse blowing

[Antares]

I recently added an Intermatic T101 mechanical timer, and now about once a week the 20A fuse that is in the circuit blows out. Before adding the timer I never blew a fuse. I tested with an ammeter, with the pump on it draws 10.6A pre-timer and 10.4A on the pump side of the timer. I have a Hayward 1HP PowerFlo II pump.

currently the electrical is set up like

house box > fuse/switch box in garage > GFCI outlet > timer > pump

The timer is hard wired in with 10ga wire connected to the load side of the GFCI outlet.

I'm totally stumped as to why this is happening since I have tested all of the connections and everything is set up correctly. Any ideas? Should I move the timer to be before the fuse box and GFCI?

 

[Bama Rambler]

Is the fuse that's blowing on the timer itself or elsewhere?

It appears to be wired correctly.

From your description it sounds like the timer has to be the problem, but we'll know more once we know exactly what is failing.

 

[Antares]

There is no fuse on the timer itself. It is this thing wired in with the conduit...

 

[TizMe]

In the picture of the switch thingy it says 15amps max but your saying it blew a 20amp fuse ? Is there anything plugged into the GFCI outlet drawing power?

We had an electrician come to the house and run a line to our storage shed with 60 amps available to us for the pool. Then off that he ran a line to the pool for the filter to run on I think 20amps (would have to double check that)
but he said it would be more than ample for what we needed up there.

 

[Antares]

The one that I have is 20A. It's also interesting to note that I have never tripped the breaker in the house for this circuit.

Nothing else is plugged into the GFCI. While I would like a new 60A circuit run to the garage, I doubt that would fix my current (HA!) problem.

I am going to take apart the fuse box tomorrow and check the current at that point..

 

[Durk]

Are you using slo-blo or regular fuses? A time delay fuse of 20 amps is appropriate for a 1.5 hp 110 VAC circuit assuming the wiring (12ga. or better) is sized appropriately. You are using a switch/fuse combo sized for 15 amp, but the risk of failure there is probably the switch, not the fuse part. Still, if I've got a 1.5 hp motor on a 15 amp switch that needs a 20 amp fuse, I would review the whole circuit for load size capability.