Hot water going cold

[Johntheo5]

Of course. Tomorrow I will send a video.

What I did was I ran the hot water (mixer tap) in the kitchen - had it running full.

Then I opened that blue value fully and the water flow was very high (from boiler I can see the kitchen tap)… that’s when the temperature on the front of the boiler went from like 55 to 0 instantly and as I continued running the hot water the display remained at 0 and the water remained cold until I started to close it down… I had to fiddle with it for a bit though as the boiler was hissing at some points so I kind of moved the value until that hissing went away and the boiler sounded happy…

I’m not sure though, that’s the only value the plumber told me about. So I do not touch any others!!!

Is the "55 to 0" display the one showing 54 in post #30 attachment? and does yours actually display 0 or does the display just go blank"
You might also take a photo of that blue valve when its opened fully.

 

[Jbcory74]

Can’t add video… this is the hot water display kitchen tab is running. Took photo and now the boiler display is on 53 and water is hot…

Will post another photo now two secs…

 

[Jbcory74]

Valve when the water is at 53-56 on display

 

[Jbcory74]

Valve opened and this is now the display… hot water tab in kitchen is now cold!

 

[Jbcory74]

Let’s see if this video works…

Linked to Google Drive…

https://drive.google.com/file/d/1ThoScm3CFjTmQRGzw2WqUlswJ8FsaGba/view?usp=drivesdk

I’ve just run the shower (and the water went warm then ran cold again)

 

[Johntheo5]

Thanks, saw the video, must go out for 2 hrs or so but can you do a few more tests
One: ensure the kitchen tap mixer is turned to fully hot then shut the valve fully, check that water stops flowing from the kitchen tap, also open the BATH HW tap to ckeck for (no) flow, then shut it.
Repeat the two video tests above that gave 0 and ~ 50/55C and get a container of any known size and time in seconds how long it takes to fill in both cases.

 

[Jbcory74]

Kitchen hot water tap one full - boiler valve now off and kitchen hot water has stopped

Bath HW not working either with valve closed

Same as the bathroom sink - no hot water

 

[Jbcory74]

4 seconds and 40

This is the hot water in kitchen when it’s actually hot

 

[Jbcory74]

Video

https://drive.google.com/file/d/1HdfR33SOLtUiegOdhX_MVswklJXRppEO/view?usp=drivesdk

 

[CountryFan]

When it goes to 00 on the boiler display and goes cold, does the boiler fire back up at all?

 

[Jbcory74]

Not at all. That’s when the flow is fully open.

But I’ve never let it run for like 10 minutes only just 2-3 minutes but it doesn’t move from 0!!

When it goes to 00 on the boiler display and goes cold, does the boiler fire back up at all?

 

[CountryFan]

Not at all. That’s when the flow is fully open.

But I’ve never let it run for like 10 minutes only just 2-3 minutes but it doesn’t move from 0!!

If you’ve checked every hot water outlet when the valve is closed and not water is at the outlets, it’s either overheating and needs chance to cool down or could be an issue with the flow sensor.

 

[Jbcory74]

I will try this now…

When it comes to mixer taps I just set them to as hot as possible yeah?? Will report back now!!

 

[Jbcory74]

Update.. I can’t the washing machine is on now will once that’s complete!!

 

[Johntheo5]

4 seconds and 40

This is the hot water in kitchen when it’s actually hot

Thats around 8.52LPM and requires ~ 22kW in heating from 18C to 55C so quite normal IMO, did you do the kitchen tap flowtest with the valve full open and HW temp at 0?

The minimum flowrequired to fire/keep the boiler firing is ~ 2/2.5LPM so the flow switch shouldn't be a problem but on the other hand the bath tap which should have a much higer flowrate when full open doesn't run cold, can you measure this flowrate as well.