This is an email I sent out last year. Hope it helps.
Preparing for the Winter - Feeding
It is considered that for overwintering, hives should have at least 30lbs of honey on them, preferably more. If this is not the case, then you will need to feed your bees.
A full national frame weighs about 5 pounds and a 14 x 12 frame full of honey weighs 7 pounds. If this all gets too confusing then bear in mind that if you can easily lift your brood box up, then the bees do not have enough honey. If the hive weighs a lot and you find it difficult to lift up, then the chances are they will be alright for food.
We still are not at the end of September so you still have time to feed the bees if necessary. A thick syrup is recommended. You can make this up easily by using a 1 kg bag of sugar and a litre of near boiling water (or 2lbs of sugar to one pint) and then multiply up the quantities for the extra weight you want to put onto your hives. The weather is still warm enough for them to be able to convert this sugar into stores.
I have started to see bees with K wings in my hives. This is an indication of acarine mite. However I am not too worried as I treated the bees with Api life Var and so the varroacide will have killed the Acarine as well.
Malcolm Wilkie August 31st 2017