THERMSAVER 70/90 LOW DHW FLOW/PRESSURE

[NACD]

Re Thermsaver 70/90 external boiler. The boiler is working fine on the heating side but the dhw flow/pressure is very poor(approx 40 mins to fill a bath).Can anyone suggest a reason for this .The mains feed to the boiler is 3 bar with a flow rate of approximately 17litres / min which seems more than adequate.This is a soft water area and the boiler is regularly serviced.Any help with this problem would be much appreciated.

 

[oilhead]

Where is the thermostatic blending valve set? If on max, then can you manage with a lower setting? None of the literature gives a performance figure, but most oil combis are pretty good. One other point, as an external boiler, how much insulation do you have around it? Also, what temperature are you running the boiler at? The incoming water to an external boiler will be significantly lower than an internal one, which also affects the delivery temperature.

 

[Boilerman2]

Slow running Hot Taps = Scaled up plate Heat exchanger (very common on oil combis in hard water areas!!)

 

[NACD]

Thanks Oilhead for your reply, the boiler is well insulated and I think the mixer valve is set to maximum I also think the boiler is set to 60 deg.Do you think the flow will increase if I drop the temperature by say 5 deg?.Iwill try and get these settings changed and see if the flow increases.

Thanks Boilerman 2 for your reply somone else has suggested the heat exchanger might be the problem ,but this is a soft water area so scale is not a big problem here .Could it still be possible that the heat exchanger has become blocked by other means and would you advise replacing with a new one?.

 

[oilhead]

How does the hot flow (volume & pressure) compare with the cold flow. If broadly similar, then heat exchanger probably is o.k. Turn up the boiler temp to 70-75 and see if it makes any difference. Firebird boilers which have an automatic DHW stat get the store up to 90C.