Hot Water Only Warm in Bathroom

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Time to get a thermometer. Normally the HW temp at the sink would be unfettered and similar to the HIU. Check that temp. 50-51deg at the HIU source is about right.

Then check output at the basin, if the TMV is set correctly then that shouldn't rise any higher than 48deg. Can you post a pic of the TMV (blending valve) behind the basin, close enough to show any markings?
The shower mixer up to the temp lock shouldn't be much higher than 38Deg, with the temp rising once you press the lock and turn it up further. When the button is pressed on the shower mixer and turned up, if the hw temp to the shower is higher, then the shower temp should rise, if it doesn't then that is being restricted by the incoming hw temp or the thermo valve itself.
 
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If the temperature leaving the HIU is still 50/51C then that should be adequate to give at least 45C after the bathroom basin TMV if its set to this temperature, can you shut off the cold water to the kitchen and bathroom and just feel the outlet from the basin tap, if the HIU outlet is 50/51C and the basin TMV setting is say 38/40C then you will get no water from the basin tap , if you do it means that the HIU outlet temperature isn't 50/51C, but if you still (and you should) get hot water from the kitchen tap then it obviously is the bathroom basin TMV and shower TMV that are set too low.
So turned off cold water feed at the HIU and tried both kitchen and basin/shower and after turning off cold pipe no hot water was coming through on both the bathroom or kitchen but cold water was at both. I touched the pipes in HIU and ones I turned off were cold while other 2 felt hot so was the correct taps. Not sure how this system works though as HIU feeds hot water and underfloor heating only while cold water and waste is via standard pipes and billed via water company instead of heat network.
I not removed the tiles so cant feel the pipes.
 
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Time to get a thermometer. Normally the HW temp at the sink would be unfettered and similar to the HIU. Check that temp. 50-51deg at the HIU source is about right.

Then check output at the basin, if the TMV is set correctly then that shouldn't rise any higher than 48deg. Can you post a pic of the TMV (blending valve) behind the basin, close enough to show any markings?
The shower mixer up to the temp lock shouldn't be much higher than 38Deg, with the temp rising once you press the lock and turn it up further. When the button is pressed on the shower mixer and turned up, if the hw temp to the shower is higher, then the shower temp should rise, if it doesn't then that is being restricted by the incoming hw temp or the thermo valve itself.
Hi
I not removed the tiles under basin so not actually seen the TMV under basin. Only been turning tap and shower on and off.
So currently on the mixer shower if you put temp dial to max without pressing button then its warm and if you press button and turn it up further temp does not change.
 
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I not removed the tiles under basin so not actually seen the TMV under basin
TMV's (blending valves) are meant to be accessible so they are serviceable and should be able to be adjusted if necessary, so something isn't right there.
if you press button and turn it up further temp does not change.
If that's the case then the valve isn't able to increase the temperature any more, so I would suspect that the HW isn't getting to the shower hot enough. Is it a bar mixer?
 
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TMV's (blending valves) are meant to be accessible so they are serviceable and should be able to be adjusted if necessary, so something isn't right there.

If that's the case then the valve isn't able to increase the temperature any more, so I would suspect that the HW isn't getting to the shower hot enough. Is it a bar mixer?
The tile has magnets so need to remove silicone filler and then it can come off but not tried it yet. Worried I will crack it haha I am hopeless at DIY

Its a thermostatic shower mixer yes so has its own tempreature regulator. You can remove the temp control dial and then access the cartridge and the temp control valve that way.
 
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If its a bar mixer then one side of the bar (the left) may get pretty hot (unless it's a run cool valve) and the right side will be cold, how hot does it get?

You may be at the point whereby you now need to get a professional in to start tracing the pipework back and see if its the outlet at issue or not.
 
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If its a bar mixer then one side of the bar (the left) may get pretty hot (unless it's a run cool valve) and the right side will be cold, how hot does it get?

You may be at the point whereby you now need to get a professional in to start tracing the pipework back and see if its the outlet at issue or not.
Its not a bar. Its a concealed unit as below:
 
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;)

OK, so it's going to be working back through the pipework from the outlets, to establish where the HW temp limiting is occurring
Ok thanks
That wont be easy as only place to access the HW pipe is under basin. According to developer the bathroom was a pod and it has 2 hot water feeds one for shower mixer which has thermostatic adjustment and then another to basin with TMV. I may just ask plumber to adjust the thermostatic max setting on mixer and see if that helps. If it does then we also need to adjust the TMV. If it does not work then out of ideas as the pipe from basin does not go to shower so adjusting TMV wont effect the shower mixer haha
 

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