Lights 15 amp circuit dims when hot tub motor kicks, 60amp circuit?

[chadtoth24]

I have an extra 200 amp panel in aux garage and only exterior lights and hot tub are on it right now. Everything my hot tub motor kicks on, the 15amp light circuit with lights dims for a second. The tub is on a 60amp circuit. How can this happen? I thought the purpose of separate circuits is to avoid this.

 

[chadtoth24]

I have an extra 200 amp panel in aux garage and only exterior lights and hot tub are on it right now. Everything my hot tub motor kicks on, the 15amp light circuit with lights dims for a second. The tub is on a 60amp circuit. How can this happen? I thought the purpose of separate circuits is to avoid this.

Everytime the tub motor kicks, not everything

 

[pc1966]

Well somewhere you have some common impedance that is allowing the voltage in the aux garage to drop when the load is applied. Motors have a high start-up current which makes them the most common reason.

However, if it really is a 200A capable panel there is no excuse as the tub can't be taking a sizeable chunk of that much. Usually the reason is the supplying cable is not thick enough for the length even if it meets the current carying capacity ('ampicity' I think is the USA expression), but more worryingly it can be down to a bad connection and that presents a fire hazard due to it heating up.

I see you are down as USA location, so maybe one of the American members such as @Megawatt will be along with a bit more country specific advice.

 

[chadtoth24]

Well somewhere you have some common impedance that is allowing the voltage in the aux garage to drop when the load is applied. Motors have a high start-up current which makes them the most common reason.

However, if it really is a 200A capable panel there is no excuse as the tub can't be taking a sizeable chunk of that much. Usually the reason is the supplying cable is not thick enough for the length even if it meets the current carying capacity ('ampicity' I think is the USA expression), but more worryingly it can be down to a bad connection and that presents a fire hazard due to it heating up.

I see you are down as USA location, so maybe one of the American members such as @Megawatt will be along with a bit more country specific

 

[MFS Electrical]

I have an extra 200 amp panel in aux garage and only exterior lights and hot tub are on it right now. Everything my hot tub motor kicks on, the 15amp light circuit with lights dims for a second. The tub is on a 60amp circuit. How can this happen? I thought the purpose of separate circuits is to avoid this.

It could be that the main cables feeding your house are a little on the small side.
Its fairly common for high amperage inductive loads to cause a momentary dip in lighting. It doesn't take much difference in voltage to affect lighting.

 

[Strima]

Voltages could be low at the panels which would cause lights to dim when a heavy inductive load starts. Motors need a bit more of a kick to get them going and draw a lot of current when starting, this current has to come from somewhere.

 

[Megawatt]

I have an extra 200 amp panel in aux garage and only exterior lights and hot tub are on it right now. Everything my hot tub motor kicks on, the 15amp light circuit with lights dims for a second. The tub is on a 60amp circuit. How can this happen? I thought the purpose of separate circuits is to avoid this.

Even though you have a 200 amp panel, what size breaker is feeding it. All hot tubs I’ve wired was on a GFCI breaker which you didn’t mention. Not only the motor pulls a high current on the start up which has been mentioned above the heating elements also pull a high current. If your lights are dimming then it sounds like you don’t have big enough wire feeding the panel