electric waterheater

[mugsy]

hi guys, want to know if you need on expansion on a Ariston Europrisma 10 litres 2 kw. On the web site it says that you need one if your cold water draw off is close to the heater but does'nt say what distance.I'm piping a flat and will be servicing a sink and basin and is only about 1 meter away . I have but these under sink water heaters before that was servicing around seven basins but no expansion vessel. Was this because the pipe lenghts were alot longer, allowing for expasion. thanks

 

[Roger Welton]

for what it costs i would stick one in to be safe

 

[SimonG]

It's normally between 2.5m and 3.0m from unit to draw off without needing an expansion vessel.

 

[mugsy]

Thanks lads will do that

 

[AWheating]

did one a few weeks back (cant remember the make) which needed 2.5m min, so expansion vessel was fitted.

 

[ecowarm]

You can take the pipe the long way round to the tap to achive the required distance

 

[Whn1]

2.5 I think, ive fitted one before where I had no space for an expansion vessel so like ecowarm said I took the pipe the long way round.

 

[ecowarm]

Also if you need say 2.5m you can run in 22mm so you only need 1.25m approx.

 

[Whn1]

Or 42mm, I can't be bothered to work out the distance though.

 

[Guest123]

2.8m is the minimum for your heater. Why not fit an unvented instantaneous water heater instead? No expansion vessel required, connects directly to any tap and heats water instantly from the mains, a bit like a electric shower does. Works with 3.5 bar pressure and I recommend them.Wire to a fused spur box.

 

[archiedale]

never fitted a unvented under sink water heater but is a prv required ?

 

[Guest123]

never fitted a unvented under sink water heater but is a prv required ?

Only if pressure is above 3.5 bar on most heaters. Check manufacturers instructions specific to each heater. The instantaneous ones are better because they heat water on demand instead of heating stored water.

 

[lbp plg & htg]

Needs discharge then though!

 

[Guest123]

Needs discharge then though!

An Instantaneous water heater heats water as it flows through it from the cold mains and is connected directly to a standard tap. No expansion vessel is required. However, if a non return valve is fitted in the inlet feed to the heater, then a pressure reducing valve set at 3.5 bar maximum and a 6 bar presssure relief valve with a discharge to a drain must be fitted. Under normal installation without a non return valve, then these are not required, neither is a discharge to a drain.
An unvented UTC (under the counter) water heater differs from an instantaneous UTC water heater in that it requires a volume of stored water to be contained in the heater that is then heated inside the heater. Once this hot water is used up, it must then store and heat more water and depending on the kw output of the unit, this can take up to 25 minutes to reach a usable temperature. This type of heater will require an expansion vessel for runs of less than 2.8 meters in 15mm pipework, plus a tundish and discharge to a drain and a pressure relief valve.

The advantages of an unvented instantaneous heater is that it heats water on demand, i.e instantly, and does not require any additional kit such as an expansion vessel etc. while an unvented UTC heater must store and then heat water before use and normally requires an expansion vessel, drainage discharge etc.

An instananeous water heater can be installed anywhere, where a hot water cylinder and a boiler is not present. They are terrific for supplying hot water to a mixer shower and/or wash basins. For a good and satisfactory supply of instant hot water, don't install one under 9.5kw.