Pyrox Vaillant instant gas water heater Temperature control problem

[MasterPlumbersKeymaster]

I have a problem with my heater and even though I got a plumber from Pulse, he couldnt fix it . I realise that he did not have the experience as he kept going to the car to refer to the dwgs. The heater gets hot but the temperature keeps fluctating after some time. I did not have this problem for the last 5 years. The plumber who came said that the heat exchanger was okay and he changed the diaphragm. This made the water get hot but after sometime the temperature starts fluctuating again. Can anybody give me some advice or help me contact an experienced gas appliance repairer who knows this model and lives in the south eastern part of Melbourne.

[racefanoneParticipant]

Contact Hogart-Neva or Energosbit.I think what you have is a European made heater.

» This message has been edited by racefanone on 30 May 2002

[nevParticipant]

With all mechanically controlled (not connected to 240V power) instantanious hot water units, the water goes into the water section (Brass bit at bottom), The water pushes against the diaphragm which raises the gas valve( Turning the gas burner on) and regulates the water(Slowing the flow of water down to give it enough time to heat up the water).
With a new diaphragm inside the unit there should be no fluctuations after the initial 20 seconds or so of flow of water.
Any fluctuation in water flow can cause a change in temperature such as:
Someone turning on another tap, hot or cold.
Plastic tap washers in the hot water tap being used.(this is caused by the washer expanding with heat and slowing the water flow through the tap causing a change in temperature).
Old galvanised steel pipework. (not enough water pressure to hold the diaphragm at full gas pressure)
Water saver shower rose (these are designed to reduce water flow (these hot water units require full water flow through the outlet to work correctly.)
Blocked water filters in tap outlets (these also restrict water flow).

The correct way to run a shower with this type of hot water unit is, turn the hot water to full flow and adjust the temperature with the cold water tap.
Hope this helps.
A good company in your area capable of fixing your unit is Harmony heating.

[Author]

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