The castle I have can be divided into 2 or 4 compartments. But, it sounds like I should either set it to 2 or make my own for 3.
Well - I'd recommend not making too much work for yourself first time out - if you already have 2's, then work with those this coming season and test the idea out using 2x nucs, before developing it further.
I've found that two nucs over a pair of QX's works well - these are a couple of divided Cloake Boards (dimensioned for two 5-frame nuc boxes over our 11-frame brood boxes), which I can either use as pukka Cloake Boards (spin the hive around, make the upper chambers queenless using slides to start emergency cells, etc) or simply rely upon the QX's without slides to stimulate supersedure cells:
There are two further compelling reasons to use an intermediate box between the QX's which I haven't yet mentioned ...
The first comes from Walter Kelly's 'How to Grow Queens' (1942-ish)
FUNDAMENTALS OF MY SYSTEM
(1) Bees above a queen excluder, with the queen below, consider themselves queenless. To prove this, take any strong colony and move eggs and brood above the excluder, and they will proceed (during a honey flow) to build one or more queen cells and allow them to hatch out.
(2) The nurse bees that feed the young worker larva are the bees needed to start and finish queen cells. The bees drawing out comb and storing honey are not the bees for this job.
The simplest way, with the least disturbance to the colony, to get the nurse bees in a queenless state and to segregate them from the field workers and wax builders, is to move the eggs and unsealed brood above the excluder far enough in advance[*] so that these nurse bees will segregate themselves.
[*] i.e. well before the commencement of the operation - but also physically far enough apart to achieve an effective separation ?
The second follows on from this: if queen-rearing is conducted during a honey-flow, with back-to-back QX's then the little darlings will commence storing nectar within the queen-rearing box - which hasn't yet caused a crisis with my 5-frame nuc boxes, but could well do so if I were to use smaller nucs (as I'm planning to do this year). But - a super inserted between the QX's offers them a far more suitable place for nectar storage.
Do you keep the entrances to the queen castle open all the time
Yes(*) - protected by anti-robbing screens. In order to initially keep the through-draught to a minimum, I reduce the size of the bottom brood box bottom entrance as far as possible (consistent with the amount of traffic flow), and close the OMF (SBB). Later, when the queens begin laying - at the very first sign of bearding, I then open the OMF to provide maximum ventilation.
Also, do the workers bring enough pollen into the castle traveling through 2 excluders and across a honey super? I have to pull my mouse guards in the spring because they knock a lot of the pollen off and was wondering if the excluders would have the same result.
That's a good question, and a valid concern. I too wondered about this, albeit with a Joseph-Clemens queenless starter-finisher (which remains queenless all season long, and so needs a QX over the entrance to stop any lost virgins from entering) - so I made-up a rig to test this.
Here is a shot of the test rig I made (with a precision QX, 4.16mm spacing), with a drawer below to catch pollen grains in the same way as a pollen trap:
This was then fitted to a nuc hive and left in position for 10 days:
There was a LOT of traffic during those 10 days, and yet when I pulled the drawer open, there were just two pollen grains in there. Ok, so that was a vertical QX - but I can't see a horizontal QX being any different.
'best, LJ
(*) Although Kelly talks about total worker-bee separation, I've found that in practice - as soon as the colony detects that there exists an upper entrance to the hive - a small cohort of guard bees set-up station behind each upper entrance (these being 22mm circular holes). At night - especially when chilly - I've observed these bees jammed solidly within the hole, effectively blocking it off.