I have a Potterton 24 combi which is 3 years old. It has no problem providing heating but has an intermitent problem where it doesn't provide water of a high enough temperature at the bath. The boiler comes on okay when the tap is turned on but you can't always have a bath due to the low temerature. I would be grateful for any suggestions.
Combi hot water problem
- Thread starter GPM123
- Start date
J
jonseyrs
What is the hot water like at the other taps?
If boiler is a few years old and it has been fine up until recently then it could be a scaled heat exchanger
If boiler is a few years old and it has been fine up until recently then it could be a scaled heat exchanger
My conclusion is the flow rate is sometimes too high at the bath to heat the water enough. Turn down the flow rate!
I am speculating that variations in supply pressure due to area or neighbour demand is causing different flow rates at different times.
Your boiler will only heat 8 litres per minute!
Can you measure the flow rate to this bath tap?
Tony
I am speculating that variations in supply pressure due to area or neighbour demand is causing different flow rates at different times.
Your boiler will only heat 8 litres per minute!
Can you measure the flow rate to this bath tap?
Tony
no such animal
balls try 9
novel as the boiler don't exist
why not change or throttle down the offending tap
i rest my case
J
jonseyrs
If for the past 3 years your hot water has been fine at the bath hot tap and recently the temperature has got worse then this is due to a lightly scaled heat exchanger regardless of the basin and kitchen tap. Cranking the flow rate down will work but it will shorely get worse over time. If the bath tap has always been poor since day 1 then the flow rate is highly likely to be the probelm at the bath tap.
I doubt you have a scale inhibitor on the cold mains supply to the boiler.
I doubt you have a scale inhibitor on the cold mains supply to the boiler.
kevplumb said:
The boiler can only manage about 8 litres per minute in this context. Of course at 35°C rise it will give 9.3 li/min
People expect to fill a bath with water at about 45°C to take account of loss of heat in heating the bath itself and cooling during the 10-15 min waiting until its full.
With water coming in at about 5°C that requires a temperature rise of 40°C and so the boiler will only give about 8 li/min.
Tony
J
jonseyrs
Yet nobody knows if the boiler has been like this since day 1 
I have reduced the flow rate and the temperature increases. I think this may be the problem, however I have to reduce the flow substantially for the temperature to rise significantly. This is not a problem I have had in the past.
Thanks for the responses
Thanks for the responses
Perhaps the incoming water temperature has not been so cold before?
Why not measure the flow rate in litres per minute so we can confirm that we are correct.
Re Chris's posting that Potterton "claim" 9.8 li/min at 35°C we all suspected that potty didn't understand physics. Odd that they got it right before on the Lynx and Puma though! Perhaps they got a new writer?
Tony
Why not measure the flow rate in litres per minute so we can confirm that we are correct.
Re Chris's posting that Potterton "claim" 9.8 li/min at 35°C we all suspected that potty didn't understand physics. Odd that they got it right before on the Lynx and Puma though! Perhaps they got a new writer?
Tony
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