Dual grow room = twice the number of lights - possible?

Im about to start a grow in a room on a 10 amp/220V circuit, and I'm hoping to be able to run two alternating rooms on 12/12.

I haven't measured the voltage yet, but most likely its somewhere between 210 and 230, which means I have 2100W to 2300W to play with. Using only 80%, that comes to 1680W to 1840W.

If I maximize it with two rooms of 3-4 x 400w in each room, that means I don't have any extra watts for a space heater for when the lights are off. Keeping the extraction fans on alternating timers, is it possible to vent hot air from the lit room to the dark room, just to keep the temperature up?
I'm aware that there could be some RH issues, but this is not to design the perfect room, just to get things going.. - possible?

Do I need the extraction fan running when the room is dark, as long as it gets some circulation from the lit room? If I have two smaller "bathroom style" fans, blowing each way, I wouldnt have any issues with negative pressure working against the extraction fan.. or?

Do I need to start the lights on separate timers, a minute apart, or will the fuse be able to hold during startup, using 80% of the total amps?

Will be using magnetic ballast btw.

How do I edit my post?

Space heater with no one there = fire.

Been awhile but some winters space heater fires are on the news. Plus thet glow = hermies.

Perhaps space heater is not the right word.. read: "heating device"

Thet grow?

Ah, glow.. nevermind

How do I edit my posts? Am I blind, or is it not possible?

Can't edit until you reach a certain number of posts. Can't remember how many.

smart start digital ballasts

smart start digital ballasts

https://www.soldigital.co.uk/howitworks.php?pID=2

Magnetic ballast are double amps on start up !

back to back will work

back to back will work

use a contactor switch over

Regarding ventilation if you use humidistat/temp controls
you will benefit from from extra c02 from the dark room
I ran back to back like this, In winter months with cold dry air outside the fan was quite low speed
very good C02 levels .A

10 amp circuit ?

10 amp circuit ?

when you say 10 amp circuit you mean the fuse or cable size or meter ?
which of the above is the restriction ?

I found when i moved country luckily same 220 voltage and 50 herts
But small meters 15 amp or 30 amp
but upon investigation they are actually 15 to 45 amp and 30 to 60 amp capable depends on cable size to the meter from street.A

fans in rooms back to back

fans in rooms back to back

youll need figure out how to switch fans over exhausting on temp speed control lights on room but circulating the lights off room in and out of lights on room then reverse it on light switch overs.!

I use 2 fans circ between rooms 24/7 on hand set speed control.
and exhaust far end each room up high exhaust fans and low intake level fans temperature speed controlled you can tweak it as you go A