Weil-McLain AQUA PLUS GL-E223-ADOC 0311 - Manual (Page 29)

AQUA PLUS
indirect
-
fired water heaters
— Product Manual
Troubleshooting
(continued)
1 Undersized water heater?
• There are many methods of sizing various applications, i.e. ASHRAE sizing tables or ASPE domestic water
heating design manual.
• Confirm the water demand required for the application.
• Confirm the flow rates of the fixtures.
• For example, was the tank sized for shower heads at 2.0 gpm, while the actual heads are 5.0 gpm?
• Use a bucket and a stopwatch to determine fixture flow rates.
• Evaluate the hot water usage pattern for a day.
• Is the peak demand unusually high for the application?
• Has the demand for domestic hot water changed since the system was installed?
• A bathroom remodeling project with a newly installed whirlpool tub will substantially change the
domestic water demand.
2 Boiler system improperly sized?
• Can the boiler provide the required output to meet the domestic water load? Determine the boiler domestic
water capacity, GPH, by the following:
Boiler DHW capacity, GPH =
Boiler output Btuh
Temp. rise °F x 8.33
[Temp. rise °F = Required DHW temp. °F – Incoming temp. °F]
[8.33 = Density of water (lbs/gal) x 1 Btu / lb-°F]
• Example — A single family home with a 3.0 GPM shower fixture and a 150,000 Btuh output boiler ca-
pacity.
• The shower demand of 3.0 GPM equals 180 GPH (60 times the GPM).
• Is the boiler capacity enough to deliver this hot water flow at 115°F for an extended period? Determine
the boiler capacity:
Boiler DHW capacity, GPH =
150,000 Btuh
(115°F – 50°F) x 8.33
= 277 GPH
• The boiler is capable of delivering 277 GPH (or 4.6 GPM) continuously, which is enough for this
application.
• Measure the BTU input to the boiler by clocking the gas meter or finding the oil flow rate based on nozzle
size and pump pressure.
• Does the hot water system need to be wired for domestic priority? For systems in which either the storage or
BTU’s available are marginal it is recommended to wire the domestic water heater in a priority manner.
• Is the boiler piping to the water heater properly sized to allow the required flow rate for maximum BTU
transfer? The temperature differential of the boiler supply and return water should be 20°F to 30°F.
Insufficient hot water
Part number GL-E223-ADOC 0311
29