DHW issue with DPS heatbank

[Johnykp]

Good evening guys, I've been in my current house for just over 12months and can't seem to fix the issue we have. We only seen to get half a bath of hot water before the water goes lukewarm. I have a Worcester 30cdi boiler and a dps cpc250-abbdi-laab heat bank. The system supplies 14 rads over 3 floors and 3 ufh zones, I have never had an issue with the CH. I have tried all sorts of different things but to go avail. Any ideas what could be causing the water to go Lukewarm after about 10mins?

Both stats are set at 70,the Combi sits about 84-88c, the DHW pump is a new grundfos ups2, the heat exchanger pump is a wilo rs26/6-3. The Combi has had a full service check with so issues . The system is running at 2bar and there is magnaclean installed. Both heat exchangers are 100kw.

Thanks in advance

 

[picasso]

You sure the store is full of water ?

 

[Johnykp]

Yeah, I've checked that,its full

 

[Johnykp]

Could it be an issue of 2 different pumps?

 

[picasso]

The blending valves can cause this, see if the pipe feeding it is hot when the water goes lukewarm.

 

[Dan Robinson]

What is the flow rate through the taps.

What is the actual output of the boiler when it kicks in?

If the boiler is not running full tilt the store could be depleting very quickly and not replenished by the boiler.

I Would go with either the blending valve or the boiler plate being clogged. But really one would need to make proper measurements.