I want to connect two 110vac relay in series across 230v ac supply.is it possible

 

no buy the correct relays

 

Not that I recommend doing it or ever did it, but you asked if it's possible.

I don't see why it should not be "possible". Two coils that have a certain impedance at mains frequency in series...

 

If they are identical relays, it should work ok.

 

Two identical 110V relays connected in series across a 230V supply might work, but there would be some potential safety issues:

• The insulation between the coil and other parts of the relay may not be sufficient to withstand 230V AC in the long term.
• Each coil would receive typically 115V, which is 4.5% higher than the rated voltage. More significantly, relay coil impedances are not usually very precise. If the coils had for instance 10% tolerance and each are at opposite extremes, the higher impedance coil can get 126.5V, or 15% over rating.

Finally there is a possible functional issue: I do not know how significant it may be. Some AC relays and solenoids exhibit a significant rise in impedance upon pulling in. If (for instance due to manufacturing tolerances) one of the relays was faster to operate than the other, could it be possible that the rise in impedance would leave the slower relay with insufficient current to pull in at all?