Main Dome Page

Dome Pressure Switch Trouble-Shooting

Please take a few minutes to view the following:

Note: A dome that is not pressurizing properly is most likely suffering from
excessive air loss, not a defective switch. If switch is not activating, check
for air loss First. Pressure switches seldom have to be field adjusted.

Your dome may be experiencing 1 or more of  these conditions.

1. On brand new installations (where the dome has been up for 3 days or less) the interior
air flap has not yet had adequate time to conform to the deck and create a sufficient air seal.

2. Pool water is not yet up to normal operating temperature.

3. The excessive loss of air through deck drains, pool water level overflow drains,  automatic
pool cover sumps, or other areas where air might escape from the dome.
 

When the aluminum flap is hanging
completely vertical, there is no air
moving through the white PVC tube.
The dome is probably resting on the
water at this point
 
 
 

.

Example 1:
on position
As the air pressure increases within the
dome, the bottom of the hinged air flap
moves back to the rear of the housing. 

Please Note: with the switch properly set up
(with the back of the switch in place) and 
looking through the large hole in the back of 
the switch at the bottom, you should note the
following:

A. The air flap, or pressure plate will remain 
motionless until there is adequate pressure 
to make it swing to the rear of the box. This 
is a sudden motion. As this happens the back 
of the glass bulb will strike the top of the metal
housing.Thsi causes a "jarring" action which 
combined with the change in angle of the glass 
bulb causes the mercury to flow to the front end
of the glass bulb, breaking contact and consequently turning the blower off.(see right) Again if you do not witness this action the dome is not getting to pressure and air loss is the most 
likely culprit.

B. Once the switch has turned off and as air pressure decreases, the pressure plate will begin to swing forward slowly (unlike the manner in which it swings to the rear). Once the pressure 
plate swings fully to the vertical position (example- 1) the mercury will flow to the rear of the glass tube, establish contact and activate the blower. Once the pressure plate has slowly moved tward the front of the housing, the final plus/minus 3/8" of te travel will be "free fall" causing the pressure plate to strike the front of the box which also facilitates "jarring" the mercury causing it to flow to the rear of the glass tube. 

Again: field adjustments, IE: changing the angle of the mercury switch is a last resort adjustment.
 

 
 Example 2:
off position

Slide the disc upward to DECREASE
the pressure of the dome.

Slide the disc downward to INCREASE
the pressure in the dome.

Adjustments: Door should always remain
all the way open except when increasing
pressure due to high wind conditions.