HIUs

Control Heating Return Temperatures

Consistent low return temperatures reduces costs, for the developer, the installer and the network operator.
The challenge for the designer is to satisfy everyone’s expectations and needs, including that of the user who is used to traditional high temperature radiant heating.
CP1 2020 Code of Practice lists:
  • Wall mounted room thermostat.
  • Electronic TRV heads to add timed heating periods.
  • TRV heads must be gas or liquid sensors.
  • Tamperproof return temperature limiters.
  • Pressure Independent Thermostatic Radiator Valves.
  • Using a programmable room thermostat is good solution to adding time control for a single zoned heating system.
  • Zoning of the heating is only required on large apartments and homes with a floor area greater than 150M2 *
  • Maximum design flow temperatures to be 70C, with a return temperature not exceeding 40C.
  • Bypass’s and automatic bypass’s not recommended.

To achieve the design return temperatures the system should be properly balanced and time of commissioning, and have fitted control valves that will maintain that balance during operation.

* Part L Building Regulation

Pressure Independent Thermostatic Radiator Valves (PTRV)

The Inta PTRV is a radiator valve that performs the functions of a thermostatic valve and a differential pressure regulator.

Each pre-settable thermostatic valve comes with six pre-set Kv values.

The valve comes complete with the EN215, class A efficiency rated Inta i-therm TRV valve
head.

Positioning of radiator valves for best efficiency

Reference CP1 2020 code of practice

Most efficient. Inlet at top, out at bottom.
Both valves on the same side of the radiator

Configuration for long radiators.
Inlet always at the top.

The code does not advise connections both at the bottom of the radiator, as efficiency drops by over 10%.

The flow rate pre-setting limits the maximum flow passing through the radiator and thereby ensures simple and effective radiator circuit balancing. The differential pressure regulator integral with the rad valve maintains a constant pressure differential so therefore maintaining the set flow rate.

Pre-settable dial up
Kvs settings for PTRV
Thermostatic head
temperature settings
125 l/h*7°C
235 l/h110°C
355 l/h215°C
480 l/h320°C
595 l/h425°C
6120 l/h530°C
Heat Load WFlow l/h
Kv Setting
600W20°C251
800W20°C34.52
1200W20°C53.883
1800W20°C77.854
2200W20°C94.85
2800W20°C120.686

Examples for setting the PTRV, min pressure for constant flow 0.1 bar. Heating is 60/40 with calculated *flow rated using the formula:

PositionFlow rate (l/h)
125
235
355
480
595
6120

Pre-setting instructions

The values required for pre-setting the PTRV can be easily set by using the adjustment tool available as an accessory. Set the flow rate that is to be kept at a constant value by selecting the corresponding number on the
pre-setting scale on the body of the valve.

  1. Remove the plastic cap.
  2. Turn with the tool clockwise to the position to be selected.
  3. The position will be seen on the tool through the viewing gap
  4. Refer to the tables and graph for the flow rates aligned with the
    position value.

Example calculation

Heating load = 600W

For this example, the ΔT is 15°C

Formula

Calculation

Minimum pressure to maintain constant flow = 10 kPa (0.1 bar). Set position 3