Question for the electricians on here

[Paulywood]

I have an old (100 years +) home and have been doing some improvements on it. My latest project was to tear out the lathe and plaster in the basement stairway and put in drywall. I also want to update the electrical in the basement as some of it is still knob and tube with porcelain boxes. When I tore out the lathe yesterday I had to disconnect the thermostat for the furnace as it is on the wall outside the stairwell. When I was putting it back together I traced the low voltage line down to the basement becasue there were 2 wires but only 1 was hooked up. Long story short, I have a wiring mess that I want to fix. Here is the way my furnace is wired:

There is heavy knob and tube wiring coming out of the box. It is run off a 10 amp breaker. This wire runs throughout the basement and most, if not all, of the outlets and lights are on this circuit. It runs into the far room and goes into an old fuse box. This box contains a 20 amp fuse. After leaving this box it runs back into the room that contains the furnace and panel. There it is spliced into a low voltage transformer that powers the thermostat. Then both the thermostat wire and the original power wire run to the furnace. I have a newer panel in the house (less than 10 years) and the furnace is a high efficiency model that is less than 15 years old. There are 7 empty slots in the panel. I have been trying to seperate circuits as I remodeled areas of the house. Here are my questions:

1. I believe that the 20 amp fuse box is useless and isn't doing anything. There is only a 10 amp circuit feeding it so the fuse would never melt. I want to remove this box. I want to remove this box and put the furnace on a seperate, dedicated breaker. The oulets and lights would be on there own breaker. Is there any reason I can't do this?

2. Since the furnace is being fed by a 10 amp breaker now, should I feed it off another 10 amp breaker?

3. How is the low voltage transformer supposed to be wired? Right now they literally have a taped off splice going into it. I haven't taken it apart to see how it is run but I know this is wrong. I think that they used to run the doorbell off the same transformer before but we eliminated it. Do I just run power from the box to the transformer, then continue on to the furnace, with low voltage power coming from the transformer to the furnace and thermostat? I am going to install a new, digital thermostat to replace the mercury one that is there now.

I know this is probably confusing but the wiring in parts of this house are a joke and I'm trying to get it right. Thanks for your help. I'm going to go pick up a new thermostat and some wire and boxes right now so if you can help I would appreciate it.

Nick

[Priority1]

Nick,

I was in the HVAC business. Typically a new furnace circuit would be 15 amps. The low voltage transformer powers the gas control valve. Most modern furnaces have a transformer and relay in the same location inside the furnace. The Thermostat is nothing more than a switch that controls the relay and or gas control valve. Do you have a new service for the house? If you're in doubt have someone look. If you need any help holler.

[Priority1]

Nick, Another thought. Most furnaces have a (SSU) a switch with a Edison based fuse close to what the amp draw of the furnace is. The switch is an electrical code requirement so the power can be turned off for service.

[Paulywood]

Thanks Frank. I have made some progress. I went and got a new thermostat and new wire for it since the old one had a few splices in it. After running the new wire I realized that it wasn't connected to the transformer, it was just spliced together there. Once the new wire was connected to the furnace and the new thermostat that part is taken care of. Now I am just working on the wiring for the furnace, lights and outlets. I pulled new wire for one room in the basement. This will be connected to a seperate breaker. The biggest issue I have is the fact that the power for the furnace is run off a 10 amp breaker right now. I'm not sure how many amps the breaker should actually be for the furnace. The 20 amp fuse box will be eliminated since there is no need for it. And the furnace will be on an independent circuit. At the end of all this there shouldn't be aby more knob and tube wiring in the basement. Everything will be grounded. The furnace was installed by a company in town so if I can't find the specs for it maybe they will be able to help me.

[Priority1]

When running any of the basement wiring don't staple the romex to the bottom of the joists. This type wire can't be run exposed. There is no problem using a 10A breaker with #14 wire just don't use a breaker higher than 15A. If I remember things correctly 15A for #14 wire: 20A for #12 wire: and 30A for #10 wire.

[Paulywood]

Well Frank, I'm actually stapling it to tree trunks, this is a really old house. I have been using #12 for the lights and outlets, just to be safe. You are supposed to run #12 if you have anything that produces heat (ie heater) so I just use it everywhere. I'll probably just go with the 10 amp breaker unless I find something that says to do it differently. I haven't had any issues with tripping the breaker so far and there are over 12 outlets/lights on the circuit along with the furnace so I don't foresee any problems sticking with the 10 amp. Thanks for your help.

[GLF]

Sorry Nick......been busy and have not been able to answer your questions.

The electrical code is very in depth about everything. It is there for your(everyones) safety.

Just because it produces heat does not mean it needs #12 wire. The key is the number of outlets/fixtures on a circuit. You are allowed to have 8 outlets/fixtures on a 15 amp circuit, and 10 outlets/fixtures on a 20 amp circuit.

The furnace has to be on a dedicated circuit, and I believe Frank is correct on it having to be a 15amp circuit.

Check the wire size before you replace the 10amp breaker with a bigger breaker. Frank is correct on the ampacities for wire size.

You do not want to splice your wires. If you must splice them together, it needs to be inside a junction box(4 square).

Outlets.....black to gold, white to silver, and copper wire to gound/green screw.

[Paulywood]

I guess I was misinformed on the wire Mike. That's what an electrician told me when I was working on my kitchen, he recommended the #12 instead of #14 for the outlets because of the toaster. Anyway, I'm replacing all of the wiring in the basement in order to eliminate the old knob and tube. I'm assuming using the #12 isn't going to hurt anything as opposed to the #14. I have extra slots available in the service panel so I can change the breakers/circuits out to anything I want. I won't be splicing anything, I'm trying to eliminate areas that have been spliced in. I pulled wire for one room today and will be doing the furnace tomorrow. I just don't know if I should leave it on a 10 amp breaker or upgrade to 15 amp. I can't find the manual, might have to call the Trane dealer tomorrow.

[GLF]

The kitchen requires two 20amp circuits. The code requires your furnace to be a dedicated 15amp circuit.

[Priority1]

Nick,

No matter if your floor joist are trees or milled 2X8,10,12, or the new I-joists it's not legal to staple wire to the bottom of them. If it's not practical to drill the joist you may want to run the wire in a conduit. Not following the code could come back and haunt you if you ever decide to sell the house. I know you are making things better by eliminating the old knob and tube but you still have to follow the code and accepted wiring practices.