Display And Connectors - Micronics Portaflow 222 User Manual

Portaflow 222 & 333 User Manual Micronics
1.5

Display and Connectors

The Portaflow unit is microprocessor-controlled, operated through a menu system using an inbuilt
LCD display and keypad. It can display the instantaneous fluid flow rate or velocity, together with
totalised values.
The instrument can also provide a variable current or variable 'pulse' (volumetric, energy (PF333
only), or flow frequency) output that is proportional to the detected flow rate. In addition to this, the
instrument can also be used to signal alarm conditions such as flow too high, too low or a volume
being exceeded. This output can be calibrated to suit a particular flow range and used with a range
of external interface devices, such as those found in BMS or site monitoring systems. The three
isolated outputs provided can be configured as required in any order and with any functionality as
just mentioned.
Portaflow 333 units can be used to measure energy and power. They are supplied with RTD probes
which, when properly placed, can be used to calculate energy lost or absorbed in a heater or chiller
circuit. It does this by measuring the difference in temperature between the probes, which are
usually placed on the flow and return pipes at the point of source. The unit is calibrated for ordinary
3
water but is also capable of making an estimate when the system contains a proportion of glycol .
Obviously, since this method of energy calculation relies on measuring the temperature on the
outside of the pipe, the assumption made is that the temperature drop between the fluid and the
outside wall is the same at both measurement points. With careful selection of measurement points
on pipes whose wall and lining are good thermal conductors, a reasonable degree of accuracy in
the measurement of the temperature differential is possible, however with pipe materials that are
poor thermal conductors (e.g. plastic, epoxy etc.) it is recommended that PT100 pocket sensors be
used instead. With the careful choice of sensor type and installation method, it may be possible to
install these sensors without having to interrupt flow.
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The proportions of water glycol are selected when choosing Fluid Type. The assumption is that the type of
glycol is ethylene (C H O ) with a Specific Heat Capacity (SHC) of 3.77kJ/kg⁰K, and a Relative Density (RD)
2 6 2
of 1.05 @25⁰C.
It has also been found that the SHC of ethylene glycol-based additives varies significantly by brand. For this
reason, and because the exact proportion and type of glycol being used are often not known, the energy
values obtained when using a glycol/water mix should be considered at best, only an estimate.
The SHC and RD for other fluid types should also be considered approximate. Published data for these other
fluids often varies significantly and is dependent on many factors that are outside the scope of this instrument
to compensate for.
Page 8 Issue 1.0 March 2021