Short Description

Thermostatic Mixing Valves are used to mix hot and cold supply water in required proportions to maintain the warm water outlet at a constant temperature. In addition to the temperature control function the valves incorporate a safety function that shuts off all water flow in the event of cold water being shut off.

More Details

TMV's are used to prevent scalding which can be caused by incorrect adjustment or inability to manipulate conventional taps. They are available as built in or exposed wall mounted units and have controls for adjusting the temperature and/or the volume of the water passing through the units.

TMV's are designed to deliver warm or mixed water, to an even, preset temperature and to compensate for any disturbance of pressure and/or temperature on the hot and cold water inlet services.

Installations can vary from supplying a single outlet, eg shower, with local temperature adjustment and flow control, to supplying multiple outlets eg a group of baths, showers and wash basins. In these multiple installations the warm water is supplied, together with cold water for local mixing and flow control, ie the mixing valve controls the maximum temperature for safety reasons

Thermostatic Mixing Valves are used in many commercial and industrial situations eg. Hospitals both public and private, nursing homes, hostels, hotels and motels, aged care facilities, educational facilities, government and non government homes for disabled, jails and detention centres, etc.

The appropriate outlet temperature depends on the intended usage and is, in a lot of instances, established by Health Regulations or Industry Codes of Practice.
Operating and control parameters are nominated by AS 4032 "Thermostatic mixing valves - Materials, design and performance requirements"
Installation requirements are covered by AS 3500 "National Plumbing Code"

. Legislation in NSW requires new hot water systems to be set at 50 degrees C. At this temperature it would take 5 minutes for a child to burn. (At 65 - 80 degrees C - takes 1 -2 seconds for a child to receive 3rd degree burns.)

. 43.5C is the maximum hot water settings for new childhood centres, primary & secondary schools ( A normal hot shower is 40 degrees C)

. TMVs for commercial or health care buildings are supplied with lockshield tamper proof covers. The thermostat must be located away from unauthorised access and not be able to be adjusted externally. These TMVs must be serviced annually.

TMVs may be:
(1) Exposed (valves for surface mounted situations)
(2) Fully recessed (valves fully concealed behind a faceplate)
(3) Pre-assembled stainless steel cabinets (for healthcare buildings)

Features

. Safety stop buttons (allow a maximum temperature setting - for a setting to be any higher the safety stop button must be pushed in as the control is turned).
. Lever control or 'crystal' plastic or metal knob control.
. Thermostats can control one outlet, the whole bathroom or whole house.
. Electronically programmable hot water system which provides hot water at a set temperature to the whole house. (Temperature is set via two remote controls with digital displays).

For further information check the Yellow Pages of the telephone book.
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Factors To Consider

. Ease of installation
. Cost of installation
. Compatibility with water pressure system (some only work on mains
pressure hot water)
. Ease of grasping controls
. Ease of adjusting controls
. Ease of maintenance