Hot water cold after 1 shower

[karlpestell]

Hi All

Got a problem with our hot water/heating whereby the hot water goes cold after 1 shower (average time running water).

We have a Worcester Bosch boiler with cylinder and cold water tank etc etc. the shower is an aqualisa power shower which obviously is powerful and does pump the water faster, but I wouldn't expect this to drain the tank.

After one shower, we'd wait for 20 mins or so and the water would still not be hot.

New 3 port valve fitted recently and tested with just hot water/heating and all fine.

Any ideas?

 

[mfarrow]

What is the set temperature of the cylinder thermostat?

What is the set flow temperature from the boiler when calling for hot water?

Is the controller correctly calling for hot water heating when the thermostat clicks closed, and the boiler continues heating until the thermostat is satisfied?

You may need to increase one or both of the above two settings to ensure respectively that you have enough hot water in the tank for the second shower (less will have been used because more cold mixing would be going on), and the replenishment rate is high enough.

 

[karlpestell]

Increased the cylinder stat a few weeks back to 75 ish in the hope that would get around the issue.

I've got no idea round the calling for hot water, how do I find that?

As far as I know it's working, but I'm no heating engineer and can only go based on the tests I've done in terms of turning off the heating and doing only water, vice versa, then both and once. All of these work fine via the 3 port valve.

There is a dial on the boiler itself, tried turning that up too, but not sure if that's water or heating related... Or both?!?!

 

[mfarrow]

What the dial does depends on the WB boiler you have. Turning the cylinder stat to 75 will only mean the boiler/pump are being told to heat the water cylinder indefinitely - it is highly likely your boiler is set lower than that temperature, so all you're doing is cycling water round the coil, with the boiler thinking it's up to temperature and not doing a lot for most of the time.

Your boiler needs to be set at least 10 degrees higher than your cylinder. Knowing what both are doing is critical to getting it right. If you don't know your boiler set temperature turn the thermostat down to 60 for now and stop wearing out your heating system.

 

[ALCPlumbing]

Is your cylinder thermostat located far enough down the cylinder. It needs to be between about 2/3s and 3/4s of the down from the top of the cylinder. Or about halfway between the flow and return to the coil. If the stat is much higher than this you won't be getting a full cylinder of hot water. Otherwise I would suggest that the stat is faulty and is being satisfied much earlier than it should. Is your boiler turned up high enough?

 

[JohnD]

What colour and size is your hot water cylinder? (This is not a joke)
How near the bottom is the thermostat?
No point in turning the cylinder stat above 60C
What temperature is your boiler set to?
Was it any better before you had the radiators on?

Run your shower into a bucket and time it. How many litres per minute does it deliver?
How many minutes is "average time?"

 

[karlpestell]

Hi

Thanks for the replies, much appreciated.

I am not at home at the moment but looking online, it looks like we have a Worcester Bosch Greenstar 18Ri boiler. Based on the literature online, it says the temp gauge on the front of the boiler ranges from 35 to 82°C. I'd say its about half way so set to around 60°C.

Ill check cylinder when home.

Thermostat is sitting around a third up from the bottom.

I will lower the stst down to 60 when home again.

To be honest, I think the water was better when the rads werent on, but never tried it to test... can do, no problems.

I will test the output tonight... its a fairly good flow rate due to the pump.

Thanks again.

 

[JohnD]

do you remember what colour the cylinder is?

 

[karlpestell]

do you remember what colour the cylinder is?

I will look tonight... I wouldnt like to guess.