Vaillant Turbomax 282e diaphragm

[Johntheo5]

I was reading a few bits and pieces on other threads/sites, this boiler apparently doesn't have a DHW flow temperature sensor but derives it from the primary flow and return sensors, one poster said the boiler cycled when both of these approached 75C, a new PCB finally cured his problem.
The DHW setting range is apparently 35C to 65C., setting 1 to 9? on your boiler so the recommended setting of 6 should be 50C.
I would suggest opening the hot tap fully, turn the boiler DHW control to minimum, 1 = 35C, measure this flow rate and temperature (if possible or estimate it) if the boiler runs continuously take a photo of the gas meter and say after exctly 120 secs take another photo, a few calcs will then tell something.

 

[Johnking]

I was reading a few bits and pieces on other threads/sites, this boiler apparently doesn't have a DHW flow temperature sensor but derives it from the primary flow and return sensors, one poster said the boiler cycled when both of these approached 75C, a new PCB finally cured his problem.
The DHW setting range is apparently 35C to 65C., setting 1 to 9? on your boiler so the recommended setting of 6 should be 50C.
I would suggest opening the hot tap fully, turn the boiler DHW control to minimum, 1 = 35C, measure this flow rate and temperature (if possible or estimate it) if the boiler runs continuously take a photo of the gas meter and say after exctly 120 secs take another photo, a few calcs will then tell something.

Thank you. I will have to leave this for a bit now as I'm on hols but I'll do all that when I get back and @ you. I appreciate the help!

 

[Johnking]

Just returning to this as I said I would and mostly when people say that you just see the end of the thread!

Having swapped out the shower head for one that permits a greater flow, my shower is fine. I've not stress tested it by getting toilets flushed etc, but I'm optimistic. Also slightly peeved that I spent so much time and money on the boiler, which was likely fine.

 

[Johntheo5]

What flowrate does the boiler show when the shower is running at 8LPM, it showed 6.5LPM with a ~ measured shower flowrate of 5LPM, post #22.

 

[Johnking]

I don't understand the question!

 

[Johntheo5]

I don't understand the question!

I was incorrectly reading that the 6.5LPM at the boiler was actually displayed as a boiler flowrate but obviously not,

This (and sorry earlier person for not trying) has helped. The minimun flow at the boiler is 6.5l/m. In the upstairs shower I was getting about 5l/m with the thermostatic mixer at ful-hot, and the same at full-cold. BUT I tried it with the shower head off and I got the full 12l/m so swapped it with a different head and that's giving me 8l/m so I'm hopeful.

Just returning to this as I said I would and mostly when people say that you just see the end of the thread!
Having swapped out the shower head for one that permits a greater flow, my shower is fine. I've not stress tested it by getting toilets flushed etc, but I'm optimistic. Also slightly peeved that I spent so much time and money on the boiler, which was likely fine.

Yes, I get the cycling. The tap (next to the boiler) is a two lever mixer and I noticed it was putting cold water back pressure on the DHW so I added a check valve to the DHW on the tap.

You have increased the shower flow to 8LPM by installing a different spray head and adding a check valve to the DHW on the tap, if you keep opening this tap slowly then the boiler should (now) fire up at say a minimum of 3 to 3.5LPM, say 3.5LPM, (theoretically, should fire at 2.7LPM) the temperature will then rise to 63.5C with a boiler min output of 11kw and a now mains temp of 18.5C, maybe you should try this but set the DHW control setpoint to max, 65C or index 9 on your boiler?.