HORNE TMVs may be used with combi-boilers or instantaneous water heaters, with one important caveat.
Due to the fact that, with these devices, outlet temperature can be heavily influenced by flow-rate; the commissioning instructions should be very carefully followed.
It is especially important when commissioning the TMV that it is adjusted DOWN to temperature. For example, to set the TMV to 41°C, first adjust the valve so water outputs at 46°C. Then adjust the valve down to 41°C. This will ensure that the TMV is not mistakenly left on an over-high setting due to the incoming water at commissioning being only 41°C.
Failure to follow this procedure could easily result in a situation where the TMV does not protect the user from scalding.
Normally, Yes. The HORNE point-of-use TMVs, up to and including DN20, will usually maintain an outlet temperature very near to the set-point (the temperature set by the adjusting screw) irrespective of supply pressure. This is due to it incorporating a high-precision slide-valve, which will prevent the passing of extremely hot or cold water. This can be verified by isolating at either of the inlets and observing flow cessation at the outlet (supply failure test).
In some circumstances, however, there may be a 'transient' flow with slightly less-desirable temperatures. This is because the valve can take a second or two to 'catch up' with changing pipework/system conditions.
The use of unbalanced pressure supplies, in conjunction with low-flow terminal fittings, can sometimes cause a situation where the TMV is in a permanent state of 'catch-up'. This manifests itself as a pulsing of the flow at the outlet. It does not cause a hazard but may be considered undesirable.
In order to prevent this pulsing, either...
1> Specify terminal fittings which can pass at least 6 litres per minute at the lower of the 2 supply pressures, OR
2> Ensure that the supply pressures are nominally balanced.
Note that spray and infra-red taps normally pass very low flowrates and, if these are used, we recommend that the supply pressures are balanced.
Also, in order to minimise start transients, we recommend that there is at least 500mm of copper pipe (table 'Y' is best) between the TMV and the terminal fitting. Start transients are more noticeable with infra-red taps as they start when the user's hands are already under the flow.
A thermostatic mixing valve or shower valve is an automatic proportioning device. It has a thermostat element that expands or contracts in response to changes in the inlet water supplies temperature and pressures. As it expands/contracts, it moves a slide valve, which alters the amount of cold and hot water entering the valve's mixing chamber to maintain a steady temperature at the outlet. The animation on every Thermostatic Mixing Valve page shows this process and also how the valve reacts when there is a slow decline and failure of the cold water supply.
Hot on the left and cold on the right, as seen by the user of the shower.
The low level servicing valves may be closed. Check that the arrows on the actuators at the side of the panel are facing up and down (open), not forward and back (closed).
This is dependent on the available water supply pressures and temperatures, the number of outlets and also the required flow rate at each outlet. The Horne Valve Sizing Tool is a tool that will help you to determine the correct size of valve for your application.
See here for Installation, Commissioning, Operation and maintenance instructions for all product families. The Maintenance & Support section of the site where routine procedures are shown in narrated video clips.
Yes, Horne TMVs are not orientation sensitive and can be mounted any way up. Just make sure that you leave adequate room for servicing the valve (access to strainers and to remove the cover).
The deadleg is the section of pipe between the TMV and the outlet it is serving. The deadleg will cool to ambient temperatures when the outlet is not in use and may provide favourable conditions for Legionella and other waterborne bacteria to proliferate. The deadleg should, therefore, be kept to a minimum and must not exceed 2m in healthcare applications.
Stagnation of water should also be reduced by regularly flushing infrequently used outlets.
In order to minimise start transients, we recommend that there is 300-500mm of copper pipe (table 'Y' is best) between the TMV and the terminal fitting.
Start transients are more noticeable with infra-red taps as they start when the user's hands are already under the flow.
Some healthcare regulations may recommend a distance shorter than this due to the risk of retrograde contamination, but this should be balanced with the need to minimise start-transients for a safe and comfortable handwashing experience.
For an ideal healthcare handwashing solution, use our Optitherm tap coupled with an ILTDU. The thermostatic mechanism in the Optitherm tap is specifically designed to operate directly at the outlet; also the ILTDU is specifically designed to disinfect all downstream pipework, thermostatic mixing valve, its ancillary fittings and the outlet.
Yes, spares kits are available for all valves made within the last 10 years, and many older ones too. Generally a Seals Kit (fit every 3 years) and a Seals and Thermostat Element Kit (fit every 6 years) are available. Full spares lists can be viewed here.
See here for Installation, Commissioning, Operation and Maintenance Instructions for all product families.
The Hot and Cold supplies may be connected the wrong way around.
It is also possible that the valve is passing more flow than it is designed to, in which case it will run cold. See the sizing chart for the appropriate TMV for maximum flow-rates.
The Hot and Cold supplies may be connected the wrong way around.
See dimension drawings for each product.
We always recommend that the circulator pump is positioned on the flow. A full explanation for this is given in our Blog post Circulator Location - Flow vs Return
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