WB Greenstar 35 cdi combi --- Inadequate DHW --- HELP!

[SafeWithGas]

Only raises 10.5 LPM through 18 degrees C on max - Extensive investigations - gas pressures, fan pressure, sensors, pump, clean plate exchanger all prove correct. WB Tech' spent an hour with me on site and say it's either the main or fan PCB but they won't commit as to which. Anyone had similar problem??? Regards to all, Sam

 

[shorticus]

Only just found your post, lets see if we can help.

As you're no doubt aware you should be getting 14-15 l/m with a temp rise of 35 degrees from a 35kw, is the 10.5 l/m the highest flow rate you can achieve?

 

[mylesy]

Is it piped up correctly?

 

[aggis]

What's the water pressure like? if it's too high, the water will pass through the boiler too quickly not making temperature. Have had this a few times.

 

[SimonJohns]

I'd recommend doing a flow rate on the cold to make sure your getting te 15l a min before you blame te boiler for bot giving you enough

I can't see the fan affecting this

Pcb maybe???

 

[mylesy]

There's a service mode on the CDI which tells you the flow rate passing the turbine, think it's 4B or something. Plus try isolating the cold underneath the boiler and turn a hot tap on. If it still comes out you have cross flow. If the flow is low it should be really hot as it can raise 10 Lt/min by 45 degrees. Only if it's going through more than it can handle it would be cooler, which is unlikely too as they have a restrictor. Could be the hot water thermostat?? Whats the flow temp getting too? If it's 80 ish there plenty to heat hot water. Are you in a hard water area, could be scaled up back plate. Hard to tell without being there

 

[SafeWithGas]

Hi All, Thanks for replies............. I should have added that this boiler is 5 yrs old and until 6 weeks or so ago the client reports that the HW performance was fine..................? 10.5 lpm is the flow from the kitchen HW tap adjacent fully open.

 

[shorticus]

Hi All, Thanks for replies............. I should have added that this boiler is 5 yrs old and until 6 weeks or so ago the client reports that the HW performance was fine..................? 10.5 lpm is the flow from the kitchen HW tap adjacent fully open.

What's the flow like at the cold tap? And I know you said that the plate heat exchanger is clean but have you had it out and checked/cleaned it, also, what's the condition of the system water? If the cold tap is giving a good flow maybe there's a blockage in the hw flow path either within the boiler or perhaps the cold feed to it...