Worcester Bosch 280 - Hot Water Temperature, very Hot!

Hi – I have recently bought a house that has a Worcester Bosch 280 Combi boiler fitted and am experiencing an issue with the hot water temperature – if I run the hot tap for a couple of minutes the hot water gets up to temperature and becomes very hot, whilst this is great for washing up, I think it’s causing me issues with a thermostatic shower valve.

I have tried turning the temperature dial on the front of the boiler to minimum in the hope that the water temperature would decrease, but it doesn’t – even after leaving it running for 5 mins or so it is the still the same very hot temperature - is there a thermostat, or sensor for the hot water in the boiler that can easily be checked and replaced?

Any help appreciated

That dial only does the heating IIRC>

Relax - most posters on here are perpetually moaning that combi's don't make enough hot water

Thanks Dan - is there a way to reduce the temperature of the hot water output?

nope...well.. not strictly true, but you either need to get the flow rate increased through the boiler - or get an RGI who can do things with the gas input - but I don't recommend it.

You should be getting 11.4 litres per minute through the boiler - and that will give you a 35 degree temperature rise.

Run the bath full tilt and go and measure the number of seconds it takes you gas meter's little red dial to spin once.

If you gas meter does have a little red dial. Take a reading. then take it again two minutes later with the bath running.

Use a measuring jug or volume-known bucket to confirm the flow rate.

To be fair the flow is pretty good - no complaints really, so I guess that's a job for tomorrow then!... No doubt be back on tomorrow evening.

The problem that I'm having is that I've fitted a new thermostatic shower valve and it seems to be reacting severley to the hot water - basically as soon as I turn the temperature mixing valve on the shower to introduce the hot water, the thermostatic valve seems to open fully and shuts off all cold - meaning I've either got a hot or cold shower - nothing in between. This is the second (replacement) thermostatic valve also, so I'm confident that it's not faulty.

My theory - and please shoot me down if you the know what the problem is - is that the water temperature is above the operating range of the thermostatic valve and as such is causing the valve to either open or shut.

I'm going to get a thermometer tomorrow (bought a medical one today - only goes to 45 degrees!) - so can measure the water temperature.

I thought that these boilers were only supposed to supply water up to 55 degrees, which is why I thought there may a faulty sensor or a way to turn the water temperature up/down?

The problem is the shower valve - it's either faulty or installed incorrectly.
The whole point of them being that they accept very hot water, and blend this with the cold to ensure a constant output temperature.

Different valves will have different specifications, but all should be able to operate correctly with the hot water input up to 65C, and it is highly unlikely the water from your boiler is at that temperature. In many cases, they will work with higher inlet temperatures.

From your description, the valve is not operating correctly.
Where is the cold supplied from - it should be from the mains supply, and therefore at the same pressure as the cold.

Sorry - wan't paying attention.

hhhmmm... perhaps the boiler is not modulating properly?

A fast reacting thermostat on the hot pipe from the boiler will demonstrate a stable temperature, and with a reduced throughput from a tap, you should see the flame go up and down as the controller in the boiler compensates to maintain a steady xx degrees. It will shut the burner down if the hot water goes over 70 degrees.

Annoyingly fir us, the bit of the manual that I think has the factory hot water setting is blacked out

more testing tomorrow then - thanks again Dan

8)