OG Confusion

[likesbeer]

I'm confused (some say easily ) but the problem is I have just done my third extract brew and each time the OG is way higher than expected. My first recipe (strong xmas ale) which I got from the helpful tinternet I did as a half brew length and put it down to poor measurement. My 2nd was (strong (not xmas) ale) similar to the first but a full brew length but I missed the chrismas spices. Again OG much higher than expected/calculated. I only have a 20l stock pot so I boil around 10-15l and then water down.
Yesterdays which I will call left overs was an experiment to reduce the strength and lighten up the strong ale above recipe is;
170g black malt
170g choclate malt
170g crystal malt
3kg LME pale
(and as it was running out of time I chucked in 200g black treacle)

beer engine says OG should be 1.047 (I was aiming for 1.050 and would have added a little DME ~300g to bring it up to that point) as previous brews were higher than expected instead of putting all ingedient in the boil I waited until cooled measured OG and was then going to adjust with the DME.
But the reading I got was 1.062 at ~20C, previously when measuring I did hot and then adjusted for temp but incase I was messing that up I waited till cool.
The other two brews finished very high (just over 1.020) which I put down to the yeast giving up and getting drunk.

I calculated the grams sugar per litre and checked a chart I have and came to the same result as beer engine (no surprise there) any ideas what might be causing my high OG readings? it doesnt seem possible to me that sugar is being generated from nowhere I am sure I am weighing accuratly at least this time (with the exception of the 1.5kg tins)
Is it possible for a hydro to go wrong? Its given expected sensible numbers for the kits I have done previously
HELP!

[Jim]

You say you're using the beer engine to work out your OG? What setting have you got for the efficiency? For extract brewing it needs to be pretty high, cos you won't get any mash losses, just losses from what's in the hops and dead space in your boiler.

It's worth checking that your hydro reads 1.000 in plain water at 20C, though.

[likesbeer]

Thanks Jim for the quick response, I've just re-checked the hydro and in tap water it was about 2 points off 1 but the tap water was around 10C so correcting for that takes it back to 1.
I was using the default value of 75% as I didnt know any better but even putting it up to 90% only changed it by a couple of points to 1.048 not the 1.062 I got.
If I'm working sugar content properly 3kg LME = 2kg sugar + 200g from the treacle + (very rough) 300g from the speciality grains that I steeped for 30 mins that gives approx 110g per litre roughly equating to 1.042 close to what beer engine came up with!!!!
Maybe I need glasses and it wasnt 1.062 but I checked twice and with previous atempts also being higher than expected I was wondering if there is something I can be doing wrong that might give a higher reading. The only step I can think of is the steeping as adding extract and boiling even I cant mess that up.

For the steep I leave for 30 mins in ~68C water enough water so the it can cover the bag (3-4l) after 30 mins use a seive and leave to drain in the top while adding the other fermentables also run 1 or 2 litres of hot 70Cish water through the grains to rins them a little. Then I boil adding hops irish moss etc at the required time.

Am I doing something wrong here?

[sib67]

Could the volume of wort collected in your FV be low?

[likesbeer]

I guess thats possible, its a standard cheapy 5 gallon jobby with no graduations I have marked up 40 pints on the side in 10 pint steps, its roughly 2 inches from the top so I would have said its close to the 23litre mark maybe not spot on but not far off. All the kits I've done have been pretty much spot on what the instructions said it would so not sure