Help with Worcester Greenstar 30Si DHW temp

[AshRyles25]

Hi,

Is anyone able to give me some advice on a potential problem with a Worcester combi we looked at today please.

Customer reported hot water on bath only getting luke warm. On first inspection we found the diverter valve passing heat down the central heating flow, so we've cleaned all the crap off the paddle on the diverter and given the plate hex a clean (which was pretty clean anyway). Diverter valve now working as it should but still only luke warm at the bath taps.

When reducing the flow down to 6l/m it starts to get hotter but MI's state it should be giving a temp rise of 40C at 10l/m, which it isn't getting anywhere near.

DHW temp sensor has been tested and giving correct readings. Boiler sounds as though its fired at full rate when the taps running. Flue gases were adjusted to MI's recommendations and gas rate fine.

We tried to get a temp reading of the primary hot pipe coming from the top of the heat exchanger and looks to be reaching 50C maximum. Surely this should be a lot hotter if its then got to heat DHW in the plate. Maybe the primary flow NTC sensor???? Anyone had anything similar of offer advice?

Much appreciated

Ash

 

[ShaunCorbs]

Water mains temperature of 10 dc if so at a 40 rise that’s 50

common issue with bath taps they require a lot of flow normally fit a 10lpm flow restrictor on the hot outlet / inlet to the bath to both cold and hot

 

[AshRyles25]

Water mains temperature of 10 dc if so at a 40 rise that’s 50

common issue with bath taps they require a lot of flow normally fit a 10lpm flow restrictor on the hot outlet / inlet to the bath to both cold and hot

Cheers for the reply Shaun, the 50C is the primary flow loop temp from main hex going through the plate hex, not the hot temp at tap. Not even reaching 30C at the tap when the bath taps throttled down to 10l/m. Cold temp was 10C so with a 40C rise we should be getting 50C but not even hitting 30C.

 

[ShaunCorbs]

Was the temp dials up eg 4-5 ?

What did it gas rate out at on hot water ?

 

[AshRyles25]

Was the temp dials up eg 4-5 ?

What did it gas rate out at on hot water ?

Temp knob was set to maximum. To be honest I didn't think to gas rate the DHW, just gas rated on service mode which came out at 29kw. We tested the NTC primary sensor on top of the main hex which was giving a resistance reading matching 70-75C, yet a couple of inch away on the pipework the temperature was only 50C, not sure if that's a reasonable temperature loss as the sensor is actually in the top of the main hex and the primary pipe just outside it?

 

[ShaunCorbs]

No would expect 70 if the sensor is saying 75 etc but a 20 dc differential is a bit much