83 Ill. Adm. Code 501.150
Fixed Factor Delivery
Section 501.150 Fixed Factor Delivery
a) A
utility's regulator for fixed factor delivery shall control the delivery
pressure at the outlet of the meter to ± 1% of the absolute billing pressure
(delivery pressure (psi) + atmospheric pressure) over the range of expected
regulator inlet pressures and customer load requirements. For example, for a 10
psig service and assuming an atmospheric pressure of 14.4 psi, the regulator
shall control the delivery pressure at the outlet of the meter between 10.244
psig and 9.756 psig.
b) A
utility may use fixed-factor delivery at delivery pressures of less than or
equal to 15 psig. At pressures above 15 psig, a utility shall not use fixed
factor delivery except for company-use metering that was in place on January 1,
2017.
c) A
utility shall determine fixed factors for billing by measuring the pressure at
the meter outlet with a calibrated pressure instrument while the regulator is
delivering a steady flow to the meter, but at a flow rate that is less than 90%
of the meter's capacity at the designated fixed-factor operating pressure.
d) Whenever
a utility performs regulator or meter set maintenance that can affect the
established fixed factor, the utility shall reestablish and reset the fixed
factor if the reading falls outside of the allowable delivery pressure variations
in subsection (a).
e) A
utility shall verify that the regulator's delivery pressure meets the
requirements of subsection (a) at least every 36 months. If a utility documents
conditions at the meter that prevent verification, then the utility may delay
verification until those conditions cease to exist or for four months,
whichever is shorter. If a utility delays verification, it shall maintain for
three years documentation of the conditions that prevented verification within
the required 36 months and provide the documentation to an authorized
representative of the Commission when requested.
f) A
utility is not required to conduct the verification of the regulator's delivery
pressure in subsection (e) for residential rate classes if those locations
serve a customer at a pressure of 5.0 psi or less and the utility uses a meter
with a rated capacity under 700 cubic feet per hour (at ½ inch differential) to
measure the residential customer's usage.
g) A
utility is not required to conduct the verification of the regulator's delivery
pressure in subsection (e) for non-residential rate classes if those locations
serve a customer at a pressure of 2.0 psi or less and the utility uses a meter
with a rated capacity under 700 cubic feet per hour (at ½ inch differential) to
measure the non‑residential customer's usage.