Luke warm hot water Alpha CB 24

[Chelt_Plumber]

In brief
Customer calls with luke warm hot water
Ran the tap and hot water was going down the flow pipe, i changed the diverter valve.

hot water stops going down the flow pipe, but still luke warm hot water

changed the domestic heat exchanger and flow switch, still no change

thermistors are fine

burner pressure is fine

no under gassing

flow rate is 9.5lm

any ideas?

 

[tamz]

Main heat exchanger. Feel the pipes.

 

[Chelt_Plumber]

red hot, 82 degrees from the main HE

plus you can hardly touch Domestic HE as its that hot

ALpha don't know either, they end up fobbing me off with MCW temp is so low due to the weather. (its been mild here for weeks)

 

[tamz]

Could be, as although the weather is mild the water temp is still down. Still only 7-8 deg here. The 9.5 output is on a 35º rise plus it may drop a degree or 2 before it reaches the taps. What actual temp have you got at taps?

 

[Chelt_Plumber]

not sure, but if you hold the dhw pipe coming from the domestic HE, it feels about about 25-30 degrees

 

[Chelt_Plumber]

basically you cant bathe in the water its not warm enough

 

[tamz]

How much do you have to slow the flow to get it up to temp?

 

[Chelt_Plumber]

to about 5 l/m and if you turn another hot tap on one of them stops

 

[tamz]

A 24 is not great but you should get more than that. You would need to accurately measure the inlet and outlet temps to check it properly but something is not right

 

[Alpha man]

What colour are the thermistor bodys?,

Have you adjusted the seasonality valve down?

Was the replacement DHW heat exchanger brand new?

Had this myself several times, only real way around it is just to slow the hw tap down quiet a bit!!

 

[Chelt_Plumber]

Hi Alpha man, the heat exchanger was brand new, as were the other parts, in the end i restricted the flow coming in by unscrewing a flathead type screw head on the PRV on the MCW inlet, it seems to have done the trick but the customer has noticed the drop in pressure, the strange thing is, is that in the big freeze we had this year and last year it was fine.