11
In-service tests
Purpose
The purpose of in-service tests is to regularly monitor
and record the performance of the thermostatic
mixing valve. Deterioration in performance can
indicate the need for service work on the valve and/
or the water supplies.
Procedure
1.
Carry out the procedure
2.
(a) to (c) on page
10 using the same measuring equipment, or
equipment to the same specifications.
2.
If the mixed water temperature has changed
significantly from the previous test results (e.g. >
1 K), record the change and before re-adjusting
the mixed water temperature check:
a) that any in-line or integral strainers are
clean
b) any in-line or integral check valves or other
anti-backsiphonage devices are in good
working order
c) any isolating valves are fully open
3.
With an acceptable mixed water temperature,
complete the procedure
2.
(a) to (c) on page
10.
4.
If at step
2.
(e) on page 10 the final mixed water
temperature is greater than the values in Table
A and / or the maximum temperature exceeds
the corresponding value from the previous test
results by more than about 2 K, the need for
service work is indicated.
NOTE: In-service tests should be carried out with
a frequency which identifies a need for service
work before an unsafe water temperature can
result. In the absence of any other instruction
or guidance, the procedure described in
„Frequency of in-service tests“ may be used.
Frequency of in-service tests
TMV3*
General
In the absence of any other instruction or guidance
on the means of determining the appropriate
frequency of in-service testing, the following
procedure may be used:
1.
6 to 8 weeks after commissioning carry out the
tests given in
2.
on page 10.
2.
12 to 15 weeks after commissioning carry out
the tests given in
2.
on page 10.
3.
Depending on the results of
1.
and
4.
several
possibilities exist:
a) If no significant changes (e.g. <
1 K) in
mixed water temperatures are recorded
between commissioning and
1.
, or between
commissioning and
4.
the next in-service test
can be deferred to 24 to 28 weeks after
commissioning.
b) If small changes (e.g. 1 to 2 K) in mixed
water temperatures are recorded in only one
of these periods, necessitating adjustment of
the mixed water temperature, then the next
in-service test can be deferred to 24 to 28
weeks after commissioning.
c) If small changes (e.g. 1 to 2 K) in mixed
water temperatures are recorded in both of
these periods, necessitating adjustment of
the mixed water temperature, then the next
in-service test should be carried out at 18
to 21 weeks after commissioning.
d) If significant changes (e.g. > 2 K) in mixed
water temperatures are recorded in either
of these periods, necessitating service
work, then the next in-service test should
be carried out at 18 to 21 weeks after
commissioning.
4.
The general principle to be observed after the
first 2 or 3 in-service tests is that the intervals
of future tests should be set to those which
previous tests have shown can be achieved
with no more than a small change in mixed
water temperature.
*TMV2: The frequency of performing the in-service
tests is 1 year maximum.
