TMV2/3 APPROVAL

SCOPE

The Thermostatic mixing valve approval administered by BuildCert provides an independent third party certification for thermostatic mixing valves against the requirements of the NHS Estates Model Engineering Specification D 08 (TMV 3 approval), and the requirements of BS EN 1111 and 1287 (TMV 2 approval).  Both documents specify exacting requirements that a thermostatic valve must comply with.  The NHS Estates document D 08 is primarily for Thermostatic Mixing Valves installed within healthcare properties that supply hot water to a point of use that is used by less able members of the NHS facility.  Because of the exacting performance requirements of the document D 08 and the need to maintain and monitor the performance of the Thermostatic Mixing Valves on a regular basis, TMV3 approved valves are considered to provide a higher level of protection against scalding.  For people who are less able and therefore not able to react quickly to a change in the water temperature the installation of TMV3 approved valves has resulted in a decline in the number of reported scalding incidents. 

Within the domestic market there is a similar risk to all members of a household from scalding especially for the younger and older residents.  Within the last two years this issue has been raised by a number of organisations including the Child Accident Prevention Trust (CAPT) and

Social housing groups.  Because of these concerns recommendations will be included within the requirements for social housing projects that hot water must be thermostatically controlled.  To ensure that suitable valves are available BuildCert has developed a TMV 2 approval that uses BS EN 1111 and 1287 to set the minimum performance levels of the valves.  Peripheral requirements for identification and supporting documentation (this detail is included within D 08 but not in BS EN 1111 or 1287) have been developed for the TMV2 approval based upon the requirements of the TMV3.

Both approval Schemes and the requirements of the approval have been fully supported and influenced by NHS Estates and manufacturers of Thermostatic Mixing Valves and their trade association TMVA.  

Types of valves

Recommended maximum mixed water outlet temperatures TMV2/3

The BuildCert/TMV Scheme recommends the maximum mixed hot water temperatures for safe use for the following installations: - 

Thermostatic Mixing Valves TMV 2 (Type 2)

The TMV2 approval confirms that the Type 2 valve complies to BS EN 1111 and or 1287 and that the manufacturer and distributor have in place a suitable quality control system.  Due to demand from industry and housing sectors such as CAPT the requirement to install a TMV2 approved thermostatic mixing valves will be recommended within the Housing Associations guidance document.  This document requires that all social housing be fitted with thermostatic mixing valves to reduce the incidents of scalding.

Type 2 Thermostatic Mixing Valves are suitable for use when the hot and cold water supplies to the valves are within the limits specified in Table 1 and where the mixed water temperature is set during commissioning at the appropriate temperature for its intended use,  (see recommendations above).

Table 1: Conditions for Normal Use 

Thermostatic Mixing Valves TMV 3 (Type 3)

Type 3 Thermostatic Mixing Valves are suitable for use when the hot and cold water supplies to the valves are within the limits specified in Table 2 below for each operating range and where the mixed water temperature is set during commissioning at the appropriate temperature for its intended use (designation) see Table 3 below). 

Only thermostatic mixing valves with no user-accessible adjustment of the mixed water temperature should be used where more than one outlet may discharge simultaneously when operated by more than one user at the same time.

Type 3 Thermostatic mixing valves having user-accessible adjustment may not be used for supplying two different maximum mixed water temperatures, e.g. Shower/Bath Mixers unless the movement of the diverter mechanism or some other device will automatically adjust the temperature to the maximum mixed water temperature allowed for that mixed water outlet. 

The maximum nominal size of mixing valves covered by this standard is DN25. 

Table 2: Conditions for Normal Use

Designation 

Some valves will be suitable for a number of purposes (or across a range of designations).

Table 3: Designation Codes

Marking

All valves complying with the TMV Scheme will be permanently and legibly marked with the manufacturers name or identification mark or a unique model reference, to enable the designation of the product to be compared with corresponding information in the approval letter.  The approval letter will describe the markings of each valve; any valve deviating from the unique model reference referred to in the approval letter should not be regarded as a Type 2 or 3 Valve.

Installation and maintenance documentation

The Scheme requires that all approved valves must include with the supplied valve an installation and maintenance document.  This document will detail the operating conditions of the valve, its temperature differential, installation requirements, method of adjusting the mixed outlet temperature, commissioning procedure and test procedure.  For full details see the appropriate web site (TMV2 I&M Documents, TMV3 I&M Documents)  

Certification

All valves certified as suitable for use as Type 2 or 3 Valves have undergone third party testing and certification against the requirements of BS EN 1111 BS EN 1287 (Type 2) or the NHS Estates Model Engineering Specification D 08 (Type 3).

Each manufacturer claiming compliance will be able to provide purchasers with a copy of an acceptance letter and certification of acceptance.  This certificate will remain valid for a period of five years subject to successful periodic auditing of the product.  The acceptance letter will indicate the means of identification and the conditions of use high or low pressure and for TMV 3 approval the exact conditions of use (designation codes) for which the valve is acceptable.

The TMV Scheme must be informed of any modifications to a valve, the modification may require that the valve be re-tested to ensure continuing compliance.   

NOTE: All valves complying with the requirements of the Scheme will satisfy the requirements of the Water Supply (Water Fittings) Regulations 1999 and the Water Byelaws 2000 in Scotland and Northern Ireland and will therefore have Water Regulations Scheme Approval.