I am looking to hook up my electric heater. I have a line that was used for an electric dryer and not being used. Can I divert the wires to the heater? I would like to hook it up with 2 hot wires with the jumpers like in the pic, and not 4 wires..the box has older fuses. What size fuse would I need?
That upside-down diagram seems to indicate you need a 60A circuit to run this heater, but a typical electric clothes dryer (in the US) only has a 30A circuit. I say circuit because you can't just change the fuse/breaker without increasing the size of the wires.
You will have to look closer at the specifications for this heater to determine the electrical requirements and then make sure that the wire size and breaker are correct for it.
Not and have it work too
This furnace wants an enormous 120 amps of electrical power just to function. I gather you do not have enough electrical service to plug it in.
Normally a furnace like this is used on a house with at least 200A of electrical service, if not 400A. If your house only has 125A or less electrical service, this furnace is not for you, and you really need to look at gas, or talk with the power company about upgrading your service.
As such, even if you could make it work somehow, the furnace would be "weak tea" and would not heat your house as you expect.
You can hack it, but it will be VERY weak
It would be possible for an electrical expert to modify it so the two 60A heaters are in series on one breaker instead of parallel on two. That will cause it to draw half the current, which will put it within the limits of the 30A wires you have going to your dryer.
Doing so is beyond your ability; get help.
Reusing the old dryer circuit
You must use exactly the same fuses that are already on the dryer circuit. Fuses and breakers protect wires.
- 15A fuse or breaker ----- protects 14 AWG copper and 12 AWG aluminum
- 20A fuse or breaker ----- protects 12 AWG copper and 10 AWG aluminum
- 30A fuse or breaker ---- protects 10 AWG copper and 8 AWG aluminum
That's it. You can't bump that just because you want to. If you do, you'll be asking your house to burn down.
If it was an electric dryer (rather large plug), it was most likely #10 copper wire, therefore a 30A fuse or breaker. However, that does not mean you can use it. Behind the socket there most be 2 or 3 insulated wires and a bare wire. If there is, then you can use it - move the bare wire to the ground bar in the panel.
If there is not a bare wire, then you must install a #10 bare wire from the service panel to the old dryer location and attach it to ground on both ends. Normally you can't just retrofit a single wire, but in this case you can because it's a ground. From that location lay new #10/3 cable to the furnace.
Looks to me as though this heater requires two 60A breakers, your dryer would only have one and it is most likely a 30A circuit, so the wire size will be inadequate for even 1/2 of your heater. You should do it per the instructions.