Combi boiler hot water pipe run in 22mm

[benjiman]

Hi all,

Ive got a 25kw combi boiler which supplies a shower with existing 22mm pipework. (Both hold and cold)

Ive put a thermostatic bath mixer on. When I put the mixer to hot the water doesnt come out super hot, more like 38 degree hot. When put in the pre set 38 degree again its cooler than what it should be.

When the hot water is on the temp on boiler shows 60 degrees..however it doesnt get to that at the shower mixer.

Is this due to the use of 22mm pipework?

When the boiler shows a temp of 60 degrees for the hw, does that mean its physically pushing out water at that rate?

Has use of the 22mm pipe works caused too much flow going through the boiler so it cant cope with the heating the water quick enough when going through the 22mm pipe?

 

[Madrab]

Well ... it could be ... is the 22mm pipe insulated? How far away from the boiler is it? Firstly I'd check the output temp and HW flow from the boiler, use the closest non thermostatic hot water outlet and see what the temp actually is, you'll probably find that it wont be 60deg at the tap.

Then you may need to calibrate your mixer, run it over a probe thermometer, set it to 38deg on the dial and see what it's outputting.

Where in the UK are you and what boiler is it?

 

[benjiman]

Its a main eco 25. Main pressure is very good, 2.5 bar.
Pipes are insulated. Its a 3 meter run to the boiler, the bath room is literally next door to the kitchen where boiler is.

On a normal hot tap the temp in hot enough that you can only touch it for a few seconds.

Although the max temp on boiler has been set to 60 degrees, ive noticed when using the bath mixer that it went up to 70 degrees at one point. Why would this be of the max has been set to 60? Something to do with the flow that is being requested from the bath mixer?

Ill get hold of a temperature sensor and try what you suggested.

 

[polesapart]

Adjust the mixer max temperature setting as advised above.

The mixer installation leaflet should tell you how.

 

[kidgreen61]

If the water is hot to taps, but not shower, then there lies your problem.
As said, re-calibrate valve, often just a simple matter of removing knob and refitting a couple of splines clockwise or anticlock, whichever is appropriate.

 

[oldbuffer]

1. It will have nothing to do with the pipe being 22 mm. That might account for a delay in getting hot, but not for never getting hot.
2. As others have said, set your new mixer shower to give 38 degrees when the knob / dial is up against the override stop.
3. Make sure any filters to mixer are clear, and that any non-return valves are operating correctly.
4. If this fails, check whether or not there is a Thermostatic Mixing Valve (TMV) in the hot feed to the bath mixer, particularly if a relatively new build.

 

[benjiman]

Thanks to all who replied.

I did as suggested and it has done the trick! I thought these mixers were set correctly out of the box but obviously not!