Hot water low temperature and pressure. (Diagram, photos and data provided).

[e5c3d4]

My hot water temperature is low. This varies at different flow rates.

At 8lpm it is around 37deg (c)
At 2lpm it is around 49deg (c)

8lpm is around the max flow rate. It is around the same flow rate / temperature at all taps (upstairs bath / upstairs sink / downstairs kitchen / downstairs toilet sink).

I have attached a diagram of the pipework going to the upstairs bath (the first outlet). This also shows the type, width and length of pipe.

I’ve also attached a photo of this pipework.

All dials on the boiler are set to max (water temp / central heating temp / hot water pre heat on). Boiler pressure is 1.6 bar.

Boiler: Independent C30 combo. Boiler was serviced in Feb. The engineer seemed to think the boiler was fine. The only figures on the report are: Operating pressure: 21.5 mbr min, 18 mar max.



Any thoughts very much appreciated.

 

[e5c3d4]

Thanks for the replies received. It’s really helpful.

Following on from my first post, I’ve now done more investigation. I’ve taken flow rate / temp readings at the boiler and just before the taps that feed the shower (to make sure the taps aren’t slowing things down).

Boiler:

Cold in: 15 lpm
Hot out (domestic hot water): 10lpm / 39 deg

Bath (pre tap that feeds the shower)

Cold: 15lpm
Hot: 8lpm / 35 deg

Does this suggest a problem with my boiler? As above, a recent service didn’t flag anything. I’d say it’s only 5-10 yrs old.

Thanks again.

 

[CBW]

Thanks for the replies received. It’s really helpful.

To be fair, there wasn’t much of a question. If you’re getting those temperatures, providing you’ve taken the incoming cold temperature then it does point to the boiler, but could be a few things.

 

[old duffer]

where does 50% of the water go? 15 in and 10 out.....

 

[Johntheo5]

Thanks for the replies received. It’s really helpful.

Following on from my first post, I’ve now done more investigation. I’ve taken flow rate / temp readings at the boiler and just before the taps that feed the shower (to make sure the taps aren’t slowing things down).

Boiler:

Cold in: 15 lpm
Hot out (domestic hot water): 10lpm / 39 deg

Bath (pre tap that feeds the shower)

Cold: 15lpm
Hot: 8lpm / 35 deg

Does this suggest a problem with my boiler? As above, a recent service didn’t flag anything. I’d say it’s only 5-10 yrs old.

Thanks again.

My mains is 11.0C just now so a 30kw boiler should flow 8.4LPM at 60C.

A flowrate of 15LPM at 39C = boiler output of 29.3kw or 19.5kw at 10LPM+39C
A flowrate of 8LPM at 35C = boiler output of 13.4kw