Lukewarm shower/bath, poor hot water flow

[Christop]

Hi, I have had an ongoing issue with a shower/bath mixer that appears to be getting worse.

The system runs of a combi boiler.

The temperatures of the bath/shower water is lukewarm at best, measured earlier as around 32 deg max and this fluctuates. The thermostatic cartridge was recently replaced due to being clogged with scale (very hard water area - the whole water system was only installed ~2 years earlier) and is configured to max heat.

The shower is concealed but I have removed the front plate and exposed the outlets. Flow rate of cold water coming out is much higher that warm (I would guess about 3-4 times as much).

I don't have an issue with other taps in the house - hot water is too hot to touch but clearly the flow rate is much lower.

I am wondering what the likely cause is with my limited plumbing experience. As stated the cartridge was recently replaced and there is a big imbalance in the flows, but shouldn't the cartridge "balance" the amount it takes in?

Is it normal for the hot water flow to be that much lower than cold water flow? Would the issue be caused by a possible blockage in the boiler (considering the hardness of the water) or could the supply pipes be blocked?

Grateful for any advice.

 

[Christop]

Ok but rather than reducing the flow of the cold water, how do I increase the flow of the hot water? I have been 3-4 bar of pressure going into the house, so why is the flow of the hot and cold at the shower/bath so different? Is this just a natural result of the pipes and the boiler? Or is there a blockage somewhere?

 

[Radioman]

Depends on how the conversion to a combined was done and it's also a function of the combi to reduce the flow and pressure of the hot. Try it and see what happens, you can reduce the flow rate of the cold but not the static pressure. This is why some valves are ported for combi and some for gravity etc.

 

[Plumbstar Tom]

afraid you cannot really improve the hot flow without the expense of moving to a fully unvented systems which will be a 4 figure sum I'm guessing. Its the way combis work, slow the flow to heat it up. You could have 10bar going into the house an it wouldn't help

 

[Christop]

Understood, but the instructions from the boiler (Ideal iMini 30kw - again can't post the link) say that the boiler can put out 12.4 l/min. At the moment its closer to 3 l/min based on what the bath puts out at hottest setting.