my House lights dim momentarily when the Spa kicks on.

It is a 220 V Spa Pack I installed 12 or more months ago

How old is your house and what is your mains circuit panel maximum capacity?

What you're seeing are the effects of pump motor start up current - which is always high, but after it gets going the amperage draw goes down to a normal level.

The spa is on a seperate metered low cost 220 V service thats runs the spa and a house hot water heater only. The service is about 20 years old and seperates at the meter. Both the house and Spa meters share the same service drop.

The service is 60Amps and the wire to the spa was changed with the spa pack. A 50 AMP SQ D GFCI Box is a foot or so away from the SPA Pack.

The dimming also occurs when I turn on the 110V blower only or the higher speed of the pump only. The Spa Pack is set for heat only when the timer call is on. Not for on for heat call

Thanks ABR

Same explanation applies. Your service drop or mains (pole) transformer is a little on the weak side.