Luke Warm Water from Hot Tap

[tyzer007]

Hello - and thank you in advance for your help on this one.

We have a Salamander Homeboost pump fitted to the mains supply to our flat. We have tanked hot water which is heated by our Valliant Ecosystem 30KW boiler. The flat has 3 bathrooms upstairs, 1 downstairs and kitchen taps.

When the Homeboost pump is on, we check the temp coming from the tank (37C) and when we disconnect the hot tap from the kitchen mixer tap and check the temp it is 16C. The same is true for one of the upstairs bathrooms. The problem seems worse for the bathtub where there are dedicated hot and cold taps compared to the mixer tap for the shower.

When the pump is not turned on, the temperature in the kitchen and affected bathroom is Ok - but not as good as the hot temperature from the other 3 bathrooms.

We think that the issue may be a mixer tap that is allowing the hot and cold to intermingle. But we don't know how to trace this to identify for sure.

According to Thames Water we are in a Pressure Managed area which means our water pressure is fine daytime, but that in the evening Thames drops the pressure and then we need a boost.

Any help is diagnosing this problem is much appreciated. Thank you!

 

[moonlight]

Just out of interest what is your cylinder stat set at?

 

[tyzer007]

Just out of interest what is your cylinder stat set at?

I don’t know where to look for that. No obvious controls without removing covers.

 

[moonlight]

Sorry its nothing you will be able to check without removing covers. It will need to be check by someone qualified. How do you know the water leaving the cylinder is 37c?

 

[tyzer007]

Sorry its nothing you will be able to check without removing covers. It will need to be check by someone qualified. How do you know the water leaving the cylinder is 37c?

Heat probe gun (IR) pointed at the pipe ...

 

[moonlight]

If your cylinder is fully heated to 60-65c I am surprised it is only leaving at 37c is that at the top of the cylinder?

 

[tyzer007]

If your cylinder is fully heated to 60-65c I am surprised it is only leaving at 37c is that at the top of the cylinder?

From the top of the cylinder

 

[moonlight]

I think it might be a good idea to get a g3 qualified engineer in to check the controls etc on your cylinder.
I have to leave now but will try and see how you get on later. Good luck.

 

[tyzer007]

I think it might be a good idea to get a g3 qualified engineer in to check the controls etc on your cylinder.
I have to leave now but will try and see how you get on later. Good luck.

Really appreciate all the help

 

[tyzer007]

Thank you to everyone who has added great help.

Last night I checked and there is no external thermostat on the megaflow tank. There is a thermostat for the immersion heater set to 4.

The Valliant EcoTec boiler has a flow temp set at 74C. On the front panel there is no symbol for “tap heat” only the boiler symbol.

This makes me wonder how the tank temp is regulated. Any ideas? And yes, this still doesn’t solve the problem of potential backflow in the piping...

Thanks again

 

[Riley]

There absolutely will be a thermostat on the cylinder. The boiler you have is likely what is known as a heat only boiler. This means that it will receive a call to heat water in the central heating or water inside a coil within your cylinder or both. This will be controlled by valves allowing the water to circulate through the radiators or through the coil in the cylinder. It will also be controlled by thermostats which will tell the boiler to turn on and off

 

[moonlight]

Have you not had the shower checked yet?
The thermostat will be on the cylinder, but not something you should be touching. You may also have a faulty valve on the cylinder but again something you are not qualified to look at, so please call in a qualified person to check these problems for you.

 

[Sondstrom]

The water is heated through the boiler (plus we have an immersion heater)

My message above was not accurate. What I meant to say was that the water leaving the tank (after being heated via the boiler) is 37C. When I check just the hot supply (isolate the cold) at the kitchen sink it’s at 16C making me think that the cold has mixed with the hot before it gets to the kitchen.

Sorry for my sloppy message

What’s the circulation temperature of the pipework from the boiler to the cylinder coil? It sounds like the first issue to sort out is why your hot water is only body temperature in the cylinder. I’d want to get the cylinder temperature to 65° or more before messing around with pipework, taps, valves & showers. It’s also worth checking your temperature equipment. 37° is body temperature: does the hot water from the top of the cylinder feel about the same temperature as your hand? It might seem like a daft thing to check but that temperature from the cylinder is surprisingly low.

 

[tyzer007]

What’s the circulation temperature of the pipework from the boiler to the cylinder coil? It sounds like the first issue to sort out is why your hot water is only body temperature in the cylinder. I’d want to get the cylinder temperature to 65° or more before messing around with pipework, taps, valves & showers. It’s also worth checking your temperature equipment. 37° is body temperature: does the hot water from the top of the cylinder feel about the same temperature as your hand? It might seem like a daft thing to check but that temperature from the cylinder is surprisingly low.

Thanks for this. The temperature of the pipes coming into the tank is approximately 65C. The boiler is set to 74C (so the actual water temp to the tank's heat exchanger seems right.) - I spoke to Megaflow and they suggested that it was either a thermostat issue or corrosion/blockage for the heat exchanger coils within the tank.

By turning on the immersion heater we got the water from the top of the tank up to 65C - so now the water coming out is absolutely hot!

 

[Riley]

Is your boiler and cylinder miles apart

 

[Sondstrom]

Is there much difference in the temperature of the flow into the cylinder and the return from it? It’s best tested from cold and the pipework should be notably cooler from the cylinder when it first kicks up and the difference in temperature will decrease as the cylinder gets hotter. If there’s not much difference then try putting some sludge remover in the heating system to give it a bit of a clean but be sure to then drain down completely and refill with inhibitor. You could even disconnect it completely and see what the coil in the cylinder looks like from the pipework connection to it.
An easy check on the thermostat is to test the continuity across the switch and turn it up and down and try to gauge whether it clicks at the right sort of temperature. If you’ve not had the immersion on and the tank is about 35° then you should hear the switch click at around that temperature on the dial.

 

[Sondstrom]

NB. Only do the continuity test on the thermostat if you know what you’re doing and make sure all of the relevant electrics is turned off.