Need help with a relay digram for a 240V sauna unit???

[jango]

Hello,

I need help deciphering the wiring diagram for a 240V sauna unit that is controlled by a Mercuri Digital Control. If you look at the picture of the diagram, I see one of the two 240V legs coming from the power supply connects to L2 on the Mercuri Digital Control. The other leg from the 240V power supply is what stumps me??? I see it goes directly to the H.L. (High Limit switch) which is located inside the sauna junction box area. It runs in series through the H.L. and back to the relay but before connecting to the relay it is in series with a 1 amp 240V in-line fuse. My confusion is, with the sauna drawing 37 amps at 240V, wouldn't the 1 amp 240V in-line fuse blow immediately? Any and all input on this would be very much appreciated. Thanks!

 

[infinity]

Does the branch circuit connect where it says Power Supply L1,L2,Ground? Turning the photo 90° would help.

 

[Ingenieur]

The fuse only sees the main relay coil power
not the heater load
the hi limit drops out the main coil
the sensor cycles the main coil to maintain temperature

 

[jango]

Does the branch circuit connect where it says Power Supply L1,L2,Ground? Turning the photo 90° would help.

Sorry for the sideways photo, unfortunately I can't edit my post. Hopefully this works. Regarding your question, infinity, perhaps I'm not reading the diagram correctly. I just don't understand how the 1 amp 240V in-line fuse comes into play?

 

[jango]

The fuse only sees the main relay coil power
not the heater load
the hi limit drops out the main coil
the sensor cycles the main coil to maintain temperature

Thanks for the reply, Ingenieur. I'm assuming this means the wiring that goes through the Hi Limit switch can be #10 ga. or smaller for that matter, since it is protected in series by the 1 amp 240V in-line fuse?

 

[Ingenieur]

Sorry for the sideways photo, unfortunately I can't edit my post. Hopefully this works. Regarding your question, infinity, perhaps I'm not reading the diagram correctly. I just don't understand how the 1 amp 240V in-line fuse comes into play?

View attachment 17994 View attachment 17995

the fuse protects the relay coil
the heater current goes thru the relay contacts
the fuse/hi limit and relay contact/heater are in parallel with the line power

 

[Ingenieur]

Thanks for the reply, Ingenieur. I'm assuming this means the wiring that goes through the Hi Limit switch can be #10 ga. or smaller for that matter, since it is protected in series by the 1 amp 240V in-line fuse?

Yes
I would use 14
but 16 or 18 will be ok
must be rated for 300 v

 

[controlled]

Thanks for the reply, Ingenieur. I'm assuming this means the wiring that goes through the Hi Limit switch can be #10 ga. or smaller for that matter, since it is protected in series by the 1 amp 240V in-line fuse?

I would say the wiring that goes through the HL is factory wiring.

 

[Jraef]

Sorry for the sideways photo, unfortunately I can't edit my post. Hopefully this works. Regarding your question, infinity, perhaps I'm not reading the diagram correctly. I just don't understand how the 1 amp 240V in-line fuse comes into play?

View attachment 17994 View attachment 17995

I think what's happening here is that you were reading the diagram wrong. You were thinking that the incoming power comes INTO that box on the bottom that is labeled "Control" at L1 and L2, then is then routed, INTERNALLY, up to the L1 and L2 terminals at the top portion that says "Incoming Supply". If that were the case, then yes, the fuse ends up in series with the heater elements (and the coil ends up in series too by the way). But if you bring your incoming lines to where is says Power Supply L1 & L2, THEN follow the wires down to the "Control" box, it makes more sense and the fuse is no longer feeding anything other than the coil of the relay.

 

[kwired]

The fuse is in a control circuit portion of the equipment not in a conductor directly supplying the heater circuit.