Manifolding; Common Faults - Rheem 613050 Service Instructions Manual

Mixing or crossed connections
If an automatic dishwasher, washing machine, flick mixer tap, tempering valve or thermostatic mixing valve is
installed there is always the possibility that the cold water could mix with the hot water through a faulty or
incorrectly installed valve. This is referred to as a cross connection. The complaints of insufficient hot water,
water too cold or excessive discharge from the pressure relief valve may be attributed to a cross connection.
The method of checking for a cross connection is:
1. Turn off the stopcock on the cold water supply to the water heater.
2. Open a hot tap. If water flow is persistent and cold a cross connection exists.

Manifolding

Very often complaints surrounding insufficient hot water in commercial installations can be attributed to poor
manifolding. In order for the water heaters to operate simultaneously the water flow through all the tanks must
be the same to ensure the temperature drop is equal across the tanks. In a worst-case scenario it is possible
for 2 or 3 of the water heaters in a bank to almost never operate. This results in an overall loss of heat input to
the water moving through the building and can be confused as the installation being undersized or a
malfunction of the water heaters. The principle of Equa-Flow is to ensure the demand on each water heater in
the bank is the same as any other. To achieve this, the following are necessary:
1. The cold water manifold must be designed to balance the flow to each unit i.e. each branch line must be
the same diameter and length and be fitted with identical ball or gate valves.
2. The hot water manifold must be designed to balance the flow from each unit i.e. each branch line must
be the same diameter and length and be fitted with identical ball or gate valves.
TM014 Rheem Heavy Duty Electric Service Instructions REV: A
Date of Issue: 10/7/2002

COMMON FAULTS

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