Range flowmax thermal store.

[siricosm]

Assuming the starting temperature was 75C, was the final temperature around 50C?

Do you happen to know the flow rate when you did the experiment?

Does anyone know the kW rating for the DHW coil in this tank?

 

[Jolead]

Assuming the starting temperature was 75C, was the final temperature around 50C?

Do you happen to know the flow rate when you did the experiment?

Does anyone know the kW rating for the DHW coil in this tank?

Yes my mains from my garden tap is low at 6lpm which is what I had the unit hooked up to. I would say the customer had 20lpm plus. My hot water from the unit started flowing at 50 degrees c. After 150l drawn off it had dropped to 33 degrees.

 

[siricosm]

Sorry I was not so clear, I meant the final tank temperature after your experiment was finished, which I would estimate was a bit less than 50C.

If my calculations are correct, then the coil in that tank is only operating at around 17kW (at T40), if one ignores any slight leakage through the blender valve. Unfortunately I can't find the rating for the power of the coil in that tank, for some reason the manufacturers don't seem to provide that, so it is hard to tell if it is working properly. 17kW seems kind of low for a DHW coil, maybe it has developed some scale?

 

[John.g]

Don't know if this is valid or not, if the coil exit temp has to be say 6C lower than the store temp then the final store temp will be 46C (for HW temp of 40C) and a 210 litre store will give 179 litres of HW at 40C from cold water at 6C.
If the store is only heated to 60C then it will only give 87 litres of HW at 40C.
Is this the point you are making?. that the store may not be heating up properly?.

 

[siricosm]

If the store temperature started at 75C and after drawing 150 liters (avg 42.37C) it should drop to around 49C based on the numbers given. However, after 150 liters it was only producing 33C water at the relatively slow flow rate of 6l/min. This might suggest the heat exchanger is not working properly, perhaps scaled?

 

[John.g]

It certainly seems fouled as it gave 3 showers originally as against 1 now.
At 33C the coil (at 6LPM) was a "11.3kw" coil, wonder how these store coils are rated, all coils will loose capacity when the store temp drops, much the same as the heating coil in a DHW cylinder, my "standard" coil will emit ~ 8.5kw with cylinder water at 15C but only ~ 2.5kw with cylinder water at 55C (boiler flow temp 70C), rapid heat recovery coils are rated with a fixed boiler temp of ~ 85C and a certain flow rate and some stores are maintained at 75C by direct gas/oil heating.