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BUNN Espress™
ES•2A™/ES•2SA™
FEATURES
IMPORTANT: None of the high pressure pumps found on the market can operate without water for a
period of more than approximately ONE MINUTE, After one minute of dry operation the pump will seize and
become unserviceable.
Should water be shut off disconnect pump from power supply immediately.
7
1
12
2
9
3
4
10
11
6
P-158
Group head (Espresso extraction chamber)
The group head-espresso extraction chamber is where the coffee infusion takes place. After extraction,
an electric pressure valve automatically discharges the accumulated pressure. When the coil (12) of the
electro-valve receives an electric current, causing the plunger (10) to move, thus closing the discharge valve
(2) and opening the water intake valve (9) allowing the water to pass towards the shower (4) through the
sprayer (3). This is when the brewing process (infusion) begins.
The bubbling effect is produced by an interchange between air, contained in a bubble formed in the
chamber, and water which progressively increases it’s pressure on that bubble. The mixture of air and water
produced then falls on coffee previously dampened by the infusion process. When the liquid extraction
process of the coffee is complete, excess pressure contained in the filter holder is then released through a
discharge valve (2). The atomizer (1) directs the water being discharged to the opening to avoid it’s splashing
outward.
WATER TREATMENT
It is essential to treat water entering the brewer to prevent lime scale build up in the boiler tank and other
plumbing. Recommended treatments are reverse osmosis or softening. Polyphosphate type treatment for
scale reduction, which works well on conventional coffee brewers, is not effective for espresso equipment.