In message , Steve
writes
On Sun, 06 May 2018 16:31:18 +0100
Harry Bloomfield wrote:

Tim Lamb formulated on Sunday :
That is what we have. Key release on the external crank access.
Very low geared so it only opens slowly.

Mine is painfully slow to hand crank too, but fine when powered. I
only found out how slow when I tried it out of curiosity, luckily I
have never had a failure. I suppose if I lost power often, I would
either make a battery backup system (it is 24v DC), or make an
attachment to fit my battery drill to crank it.

I've cranked them with an Allen key in a cordless drill.

Mine is 6.4mm 1/4"? square section and about 18" long. I suppose they
have to consider cavity wall thickness for built in jobs.

--
Tim Lamb