Does this sound safe?

[ironhat]

The shop in my garage is fed from a 50 amp breaker in the house. Every time I use the 3650 table saw with shop vac and four double tube fluorescent fixtures on, the lights dim a great deal on start up. Can I blame this on the cold temps in the shop, to some extent (40*F)? I had a licensed electrician check everything during construction and he OKed the supply line and made the hookups in the box. Incidentally, all of the above devices are on separate circuits. I know the guy and trust him but I have a real fear of electrical fires. Opinion please.
TIA,
Chiz

[drumpriest]

I'm not entirely surprised by this. Your table saw uses quite a bit more power at startup than it does once it's up to speed. This spike of power requirement is probably what's causing your light issue.

[onedash]

i dont know much about electricity besides its expensive but the house I rent has aluminum wiring and I havent had much trouble in the shop but in the house when I run the vac or shampoer the lights dim. most of the switches are screwy. When I turn them off the light stays on until I let go of the switch. So in the off position as long as its kinda pushed the light will stay on. I had one outlet in the garage that was for copper wire and the wire corroded and started smoking. So the electrician came and put a new outlet in. He used a coper outlet but ran a coper wire and pigtailed it to the aluminum with some compound to prevent problems. I have come to the conclusion that aluminim wire sucks and shouldnt even be sold. Maybe the reason I have less problems in the garage is because they are much closer to the breaker. You should see the wires in the garage. They are all going at angles across the rafters. Its nuts. im sure its probably not up to code.

[JimD]

Two 40W tubes pull less than an amp. A shop vac should be no more than 6 amps. Your BT3100 pulls no more than 20amps, even at startup (I doubt it pulls more than 15 and have used it on a 15 amp circuit). Even being generous with the extimate of the loads, this is no more than 30amps. There should be no voltage drop that would dim lights on three separate circuits. If the lights and the BT3100 are on the same circuit, the lights could dim. Maybe the lights dim if the lights and the shop vac are on the same circuit. Otherwise you have a bad connection or an undersized wire somewhere. I have my BT3100 on a 20 am circuit and my lights and DC on a different 15 amp circuit. The DC will dim the lights but the BT3100 has no effect.

Jim

[LarryG]

I'm interpreting your description to mean you have a 50A double breaker feeding a subpanel in your <s>gara</s>shop. If so you need to get your electrician to move the lighting circuit breaker to the opposite leg from the tools that have high-amp start-up loads.

I had the same problem when I rewired my shop space. Originally my 2HP HF dust collector was on the same leg as the lights, and switching it on would kill the lights. Moving the breaker for the lights to the other leg solved the problem instantly.

[ironhat]

I'm not quite sue how to answer you on that one Larry. The 60a breaker in the house is big but I don't know about it being double. It feeds a subpanel in the garage which has multiple circuits which the electrician wired in according to the liklihood of things being used at the same time. I'll ask him about the 'leg' situation in the sub. I'm ignorant when it come to panel boxes. Thanks for the info all. Time to talk to Tom the electrician.

[stewchi]

Second what Larry said.
Whenever I used my CMS in the garage when the temp was below 40deg it would go completely dark for a few seconds. My procedure was: Turn on the saw, stand very still until lights come on the continue with cut. In the summer the lights would dim but not to the same extent as in cold temp. I had cheap shop lights, better ballasts are not as affected by the cold. I only had one circuit in the garage so no chance of changing circuits easily for me.

[Hellrazor]

Your lighting should not be on the outlet circuits anyway.

4 fixtures x 2 lamps x 40watts = 320watts/120v = 2.7amps

You should put your table saw on a dedicated 20amp circuit.

[LCHIEN]

I've not measured it but the saw may draw as much as 5 or 6 times the running load at startup for a period too short to trip the breaker but long enough to briefly quench the flourescents esp. if the ligths are cold and their threshhold lowered.

I think the advice to move the lights to the other log if possible will help a lot.

ONEDASH:
regarding aluminum wiring. This was used a lot in construction in the mid-70's when there was a copper shortage. The results were so bad I believe it is now outlawed for new construction (as you wished).
The problem turned out to be the thermal expansion and contraction of the aluminum from on-off cycles and resultant oxidation made the aluminum make poor contact with the terminals on many of the switches and outlets. Of course then it heated up more and got worse fast. The result was often: Noisy contacts, hot contacts, scorch marks around outlets, and outright fires. I would NEVER buy a '70's house with aluminum wire.
What you need to do is be vigilant. One frequently used method was to carry an operating AM radio tuned between stations and put it close to any outlet and switch carrying current. If the radio picked up an increase of noise close to the outlet, then it was getting loose and dangerous. The solution is to make sure the outlets and switches had the specialty (CO-ALR? I think, your electrical suppl house should know) copper-aluminum type contacts and these are now very expensive and special order and cost maybe $8-10 each compared with $1 or $2 for regular copper only, or get this special paste for coating the contacts that will help prevent the oxidation bewteen any copper terminals and the aluminum. I think you mentioned your electrician used this when splicing to a copper wire. Good for him.

[gjat]

What you are experiencing is voltage drop due to load. A motor always draws more amps until it is up to speed unless you have a special starter system (think 'soft start' on a router). Cold affects flourescent lights and how the electrical charge excites the florescent coating which creates the glow. You have seperate circuits from a sub-panel, but they all feed from the one 50amp feed from your main panel. The saw starting up is sucking all the possible amps it can get from the 50 amp feed to your shop which causes a voltage drop to the light ballasts, droping it's voltage, reducing the charge to the tubes which are already dimmed due to the cold. You are nowhere near having a problem unless the conductors are undersized for the breaker, which I doubt, the conductor is just a little undersized when calcuated for voltage drop and power factor.