CSA C900-1:2021 pdf download.Thermal energy meters一Part 1:General requirements
The registration device itself or an appropriate associated software for use by the consumer shall allow to verify the correct assignment of single interval values or sums of interval values to rates (like the maximum consumption or the sum of consumption during daily periods), if such processed values serve as basis for the price to pay.
And if applicable other registers can also be displayed.
5.10.5 MPE
5.10.5.1 Clock
If applicable for the instrument:
For frequent time based tariff switches between registers (e.g. for day and night tariff) within a billing period, the deviation from legal time shall be one of the following three options.
Option 1: deviation less than 1 h/year
Option 2: deviation less than 6 min from legal time
Option 3: deviation less than 7 s from legal time
NOTE The above chosen maximum time deviations are derived from the physical inertia (thermal capacity to be heated or cooled) of the heat conveying liquid, within the heat and cooling circuits.For periodic interval registers for a billing period (e.g. hourly, daily, weekly or monthly registers), the time deviation shall not be more than 1 % of the length of this period. In this case the deviation of the internal clock from legal time is the accumulated deviation of all measurement periods.
6.1.1 All the constituent elements of thermal energy meters shall be solidly constructed of materials having appropriate qualities to resist the various forms of corrosion and wear which occur under rated operating conditions, especially those due to impurities in the heat conveying liquid.Correctly installed meters shall also be able to withstand normal external influences. Meters shall, in all circumstances, withstand the maximum admissible pressure and the temperatures for which they are designed, without malfunction.
6.2 Requirements outside the limiting values of the flow rate When the true value of the flow rate is less than a threshold value declared by the manufacturer, no registration is allowed.
The flow rate through a“nominally" closed valve or the movement of liquid in the pipe behind a closed valve caused by thermal expansion and contraction should not be recorded.
For flow rates greater than qs, the behaviour of the meter, e.g. by producing spurious or zero signals shall be declared by the manufacturer. Flow rates greater than qs until declared maximum flow shall not result in an error greater than 10 % of the actual flow rate.CSA C900-1 pdf download.