Trinity Lx
│
Installation and Operation Instructions
Lx – WH Series
44
Thermostatic Mixing Valve
- When the system requires water at temperatures higher
than required for other uses, such as high temperature applications typically greater than
46
o
C (115
o
F), a means such as a thermostatic mixing valve shall be installed to temper
the water for those uses in order to reduce scald hazard potential. Anit-scald devices such
as a thermostatic mixing valve allows potable water to be stored at a higher temperature
to limit bacteria growth, and allows water at the tap to be delivered at a lower
temperature to prevent scalds. Failure to follow these instructions may result in serious
injury or death.
Water stored at temperatures between 68-113ºF is ideal for bacteria growth (see Table
10-1); therefore consuming water from a Water Heater is not recommended. Consuming
water from a Water Heater may cause illness or death.
Legislation and Guidelines
- At the time this document was written, standards and
guidelines regulating the prevention of Legionella in the United States and Canada were
mostly voluntary. The American Society of Heating, Refrigerating and Air-Conditioning
Engineers, Inc. (ASHRAE) is currently in the process of converting its guideline entitled
"Minimizing the Risk of Legionellosis Associated with Building Water Systems"
(ASHRAE Guideline 12-2000) into an official standard. Consult with your local
authorities as to recommended guidelines for controlling Legionella in potable water
systems.
General Guidelines
- In the absence of a National standard or local codes, the following are general guidelines
for “good practice” on maintaining, monitoring and operating your potable water system:
Store hot water at temperatures > 60
o
C (140
o
F) for “water (potable) heating only” applications.
Store hot water at temperatures > 80
o
C (176
o
F) for “combined space heating” applications.
Store and distribute cold water at temperatures below 20
o
C (68
o
F).
System supply for uses other than high temperature applications typically greater than 46
o
C (115
o
F) shall be
equipped with a thermostatic mixing valve on the hot water outlet to reduce potential scald hazards.
Clean aerators and nozzles on water fixtures on a regular basis to reduce scale build-up.
Clean storage tanks and remove sediment. Flush storage tanks and piping systems regularly for 10-30
minutes at high water temperatures (depending on guidelines used) to rid the system of sediment and scale
that develops, typically in the bottom of storage tanks where water temperature is coolest and piping runs
where water can stagnate.
Abandoned water lines should be capped off at the distribution main, not at the most convenient place.
Avoid dead-ends in piping system. If unavoidable, provide a drainage port in these areas at the lowest point
to flush out stagnant water regularity.
Insulate DHW recirculation lines and keep pipe runs as short as possible.
Recommend annual water testing of water in your tank and piping system(s) to monitor water conditions.
Keep a maintenance record of when your water heater and storage tank were cleaned, piping systems
flushed and who did the service work.
Table 10-1 How Water Temperature relates to Legionella and Scald Hazard
Water Temperature
1
Legionella Bacteria
1
Water Temperature
2,5
Exposure Time vs Burn
5
158-176
o
F
70-80
o
C
Disinfection range
158
o
F
70
o
C
1 second - 2
nd
or 3
rd
degree burn
140-149
o
F
60-65
o
C
Bacteria die within minutes
140
o
F
60
o
C
5 seconds - 2
nd
or 3
rd
degree burn
122-131
o
F
50-55
o
C
Bacteria die within hours
131
o
F
55
o
C
5 seconds - 1
st
degree burn
68-113
o
F
20-45
o
C
Bacteria thrive and multiply
122
o
F
50
o
C
1 minute - 1
st
degree burn
below 68
o
F below 20
o
C Bacteria is dormant
111
o
F
44
o
C
5 hours - 1
st
degree burn
3,4
Notes:
1
Published by Chartered Institute of Plumbing and Heating Engineering, Databyte series, "Safe Hot Water Temperatures".
2
The elderly and small children are susceptible to bad burns at shorter exposure times than listed in this table.
3
A thermostatic mixing valve should be installed on DHW storage tanks when outlet temperatures exceed 115
o
F [46
o
C].
4
Typical water temperature for bathing or showering range between 98-113
o
F [37-45
o
C].
5
Temperature-Time-Burn Chart published by John Hopkins University, excluding notes.
