WORCESTER 24i RSF L combi

[paulbrooking]

Hi New to forum.
The 24i is giving hot water that changes temp with flow, an "boiler engineer" tells me this is normal, but because of this the shower wont work properly. The manual says the burner is modulated on hot water between 7.5 & 23 KW. I have roughly measured the heat power at the hot water tap (from flow and temp rise) and it is about 15KW at tap full on and about 14.5KW at min flow, measurement could be a bit out but it seems to me it is not modulating as it should.
With the shower I have and the flow rate with water full on the boiler power which seems to be constant is too much for the required temp rise. Is this boiler working as a 24i should ?
help please.
Paul

 

[Agile]

Probably not!

But modulation depends on having the gas characteristics correctly set in the boiler.

That's unlikely unless you have had the boiler services by an "enthusiast" boiler engineer!

A boiler I visited today had been maintained by British Gas and had the power input set about 35% low!

It also had a fault misidentified and blamed on a need for a power flush which was quoted for at about £700. The actual fault was a £35 part!

Tony

 

[paulbrooking]

Thanks Tony,
The thing I was really trying to get answered is if with this particular boiler type, the modulator will keep the water at a constant temp. (as it sounds to me it should from the manual). I have measured the water temp. on a completely unrelated combi, and it stays constant as the flow rate is changed. With this boiler in question that won't work properly with a shower, the output power remains constant and the water temp goes up as the flow is reduced.

Paul

 

[Dan Robinson]

It is supposed to try, but these boilers are pretty low rent so not going to be very sophisticated. It could also be upset by lime scale.

I would suggest you leave measuring the energy consumption to professionals .

 

[paulbrooking]

Thanks Dan,
yes I would not expect it to be perfect, but it does not seem to make any effort to adjust the output. I had to measure it myself because I need to get the shower working, and the info the boiler man is giving me does not seem correct. From my experience some plumbers do not really understand things. It was easy to measure by filling a measuring jug with water, timing it and measuring the cold water and hot water temperatures.
I found that it would be impossible for the boiler to work with the shower I have because the constant power out put of the boiler would result in a shower temperature that is too high with the flow rate of the shower. I have solved it by drilling out the holes in the shower head to increase the flow rate to one which is compatible with the boiler output.
The "expert" was telling me to fit a pressure reducing valve in the cold supply to the shower to enable better control, but this could not possibly work as i have explained.
Maybe I don't need to bother about whether the modulator needs fixing on the boiler now, but it would be interesting to know exactly how the boiler should perform.
Paul.

 

[algas]

My Daughter inherited a 24i when she bought her house, although I have serviced it the modulation on h/w mode is a little hit & miss this is due to the boiler having a twin pass heat exchanger or bi thermic I think they call them now, a half decent thermostatic shower will work well.

 

[TCCHeating]

I have measured the water temp. on a completely unrelated combi, and it stays constant as the flow rate is changed. With this boiler in question that won't work properly with a shower, the output power remains constant and the water temp goes up as the flow is reduced.

Paul

As far as i remember the 24 rsf doesnt have a temp control for hot water. It will just work on a 35 degrees rise up to a maximum temp of 55-60 degrees.

So if your cold water enters the boiler at say 10 degrees. You would expect the hot water to be 45 degrees at full flow. Therefore by reducing the water flow at the tap it is completely normal for the water temp to rise on your boiler. It should only start modulating when the hot water temp reaches the 55-60 degrees maximum

 

[paulbrooking]

Thanks aglass & TCC heating,
Yes this could be the answer that the modulator is only intended to come in above a certain temp, rather than regulate the temp. (well obviously it can only turn the power down so at high flow rates it could be off regulation). There is only one temp control (I presume only for CH) and it has no effect on HW temp. But even so I think it may not be working properly because as I slowly close the hot tap the water temperature increases right up to the point where the boiler cuts out, the water temp never gets to a point where it remains stable as I continue to close the tap. If the boiler was regulating properly would not there be at least some range where the flow rate can be changed and the temp. remains constant ?
But the temp that the boiler cuts out at does seem to be variable.

Paul

 

[Agile]

Your boiler is intended to modulate to control the hot water output temperature and has the appropriate DHW temperature sensor.

My view is that it has not been set up correctly.

Unfortunately you are probably too far away for me to directly help! You need a competent boiler engineer, not a plumber and not a boiler installer!

Tony

 

[paulbrooking]

Thanks Tony, that is what thought was probably the case.

I think I will leave it for the time being, with the shower I have it is working OK



Paul