Hot water going cold

[Jbcory74]

Oh ok, well the en-suite mixer bar seems like it’s a bit worn and loose not like before - it’s only 3 years old might be that???

Can be any mixer

 

[Jbcory74]

Hahahaha he is not!!!

Is your partner in the SAS?

Andy

 

[CountryFan]

Oh ok, well the en-suite mixer bar seems like it’s a bit worn and loose not like before - it’s only 3 years old might be that???

Could be any of them. Needs to be traced by the method I stated earlier. No I’m not local to Herefordshire

 

[Johntheo5]

There are a few fairly easy tests you can do yourself if you are up for it assuming you have single HW taps (without mixers) especially a bath HW tap.
If you have, open the bath HW tap fully, ensure the boiler DHW temperature is at its max, 65C?, measure the HW temp if you have a household thermometer, run the HW into a container for exactly 30 secs, then measure it with a 1pint milk bottle, X 1.136 to give the flowrate in LPM. While letting the HW running, take a photo of the gas meter and exactly 3 minutes later (to the very second) take another reading, shut off the HW tap.
The (my) mains temp is 18C just now so easy to do a few calcs oince you do your tests and then maybe do a few more at lower flowrates like say 17.0LPM which should give a HW temp of 50C from any 38kW boiler.

 

[Jbcory74]

This is a bit too complicated for me… but I can send to the plumber lol

Thank you though!

We have some just one HW tap - the bath, but all the rest are mixers!

There are a few fairly easy tests you can do yourself if you are up for it assuming you have single HW taps (without mixers) especially a bath HW tap.
If you have, open the bath HW tap fully, ensure the boiler DHW temperature is at its max, 65C?, measure the HW temp if you have a household thermometer, run the HW into a container for exactly 30 secs, then measure it with a 1pint milk bottle, X 1.136 to give the flowrate in LPM. While letting the HW running, take a photo of the gas meter and exactly 3 minutes later (to the very second) take another reading, shut off the HW tap.
The (my) mains temp is 18C just now so easy to do a few calcs oince you do your tests and then maybe do a few more at lower flowrates like say 17.0LPM which should give a HW temp of 50C from any 38kW boiler.

 

[Johntheo5]

Can you just open this (bath tap) fully, does the boiler fire up, remain firing, and does the water feel hot or lukewarm or does it go hot & cold.

 

[Jbcory74]

It is boiling hot… and remains it… but it’s not very high pressure.

There have been instances when it’s come cold and then back hot though. The shower is affected the most!!

I have lowered the temperature though in the boiler because the plumber said the system couldn’t deal with heating water on the fast flow… it’s in like 55 degrees now.

Can you just open this (bath tap) fully, does the boiler fire up, remain firing, and does the water feel hot or lukewarm or does it go hot & cold.

 

[robinbanks]

Or any non mixer hot tap, or even multiple taps, mixer or otherwise, set to hot

We want to know, when there is no restriction on flow of hot water from the boiler, and no TMV fiddling with the flow, what does the water temperature do? Stabilise high? Stabilise warm? Fluctuate? Etc

Also, if you can get a bucket/s and measure how much water comes out in a minute it could be helpful info

 

[HERTS P&D]

Hahahaha he is not!!!

You would say that!

Andy

 

[Jbcory74]

When you say no restriction on flow…

Does this need to be fully open?

Or any non mixer hot tap, or even multiple taps, mixer or otherwise, set to hot

We want to know, when there is no restriction on flow of hot water from the boiler, and no TMV fiddling with the flow, what does the water temperature do? Stabilise high? Stabilise warm? Fluctuate? Etc

Also, if you can get a bucket/s and measure how much water comes out in a minute it could be helpful info

 

[Johntheo5]

It is boiling hot… and remains it… but it’s not very high pressure.

There have been instances when it’s come cold and then back hot though. The shower is affected the most!!

I have lowered the temperature though in the boiler because the plumber said the system couldn’t deal with heating water on the fast flow… it’s in like 55 degrees now.

You won't have any pressure when its "falling" out of a bath tap spout but you can still have a very high flowrate. OK then, assuming its now shut off get someone to listen by the boiler and open the same tap very slowly until the boiler fires up and stays firing, then run into any known volume container and measure the time in seconds to do so.

 

[Jbcory74]

I will test properly tomorrow…

But have just under the boiler opened up the flow rate … and the boiler just shuts down (not actually) but the hot water display on the front goes to 0 and will not go warm at all…

 

[Johntheo5]

The valve you are pointing to is the cold mains into the boiler and should be fully open, the short piece of copper pipe connects into the CH return and is used for topping up the pressure in the boiler via the other isolating valve which is shut.
Can you post a photo of this "hot water display on the front goes to 0 and will not go warm at all…" also any other gauges on the boiler front.

 

[Jbcory74]

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!!!

 

[Johntheo5]

OK, thanks, can have another look tomorrow but think you need someone who knows what they are doing, will have a look at the attached later.