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Installing a Watlow 935A
PID On A Bunn ES-1A
For the uninitiated,
here's an introduction to the Bunn Espress, model ES-1A 1-group
commercial espresso machine.
Summing up the review of the ES-1A, it has everything an espresso geek
could want in a home espresso machine;
- Size & weight
- Temperature stability
- Pre-infusion
- Clean design (makes working on it a piece of cake)
- E61-type group head
- And much more
So, let's start by choosing the parts needed for the PID kit.
¹The Watlow models to
look for are 120VAC; 935A-1CC0 or 935A-1CD0. Avoid the
935A-1CC1 and 935A-1CD1 as these require a
24VDC power source.
Now, let's decide what to remove from the ES-1A & what will no
longer be needed.
- Remove all top, side, & back panels.
- Disconnect the copper tubes to the pressure stat, disconnect the
wires to the pstat, remove the pressure stat & set it aside.
- Loosen the large screw clamp (thing radiator hose clamp) holding the
thermostats against the boiler.
- Cut the wire on either side of the thermostat & set them aside.
Assemble the PID kit.
- The
Hammond 1216
panel-mount enclosure is equipped with two inserts or end
panels, one plastic & one aluminum.
- Cut a hole in the insert you'll use to accommodate the PID (I
mounted mine to one side, leaving room for the fuse holder).
- Cut a hole in the insert to mount the fuse holder.
- Cut a hole n the bottom of the enclosure for the fan (optional) .
- Line the edge of the hole with double-sided adhesive to mount the
fan.
- The area of the front panel just above where the pumps mounts behind
it is the best place to install the enclosure.
- Using a cutting wheel, remove the metal on the front panel to mount
the enclosure.
Wiring, or rather altering the wiring of, the Bunn ES-1A to
accommodate the use of a PID.
Here is a
simplified view of a wiring diagram, showing the changes needed for
this conversion.
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