Vaillant ecotech 831 - Not up to the job?

[D_Hailsham]

Why are people pointing to the boiler, when the fault is clearly a CIRCULATION/BALNCING ISSUE

Because you will never get the balancing right if the boiler is not properly set up for the available rads output.

 

[sambotc]

Is it microbore pipework with manifolds?

If circulation was OK, then all radiators would get to a similar temp but boiler would cut in and out on stat, slowing down the whole heating process.

Could even just be air if the installer hasn't cleared it properly.

Try turning all but 1 of the downstairs radiators off, if it heats up, turn it off and repeat on another until all are getting hot on there own.

 

[mickyg]

Why are people pointing to the boiler, when the fault is clearly a CIRCULATION/BALNCING ISSUE

Because you will never get the balancing right if the boiler is not properly set up for the available rads output.

Unfortunately some people don't actually work in the industry and just read about it. That leaves them without the crucial real life experience! This is nothing to do with range rating the boiler, it won't matter. Let me explain for you.
Ecotec boilers Will modulate down to the correct demand as required automatically without the need to be range rated. If the customer has more than about 8kw of output the boiler won't cause a problem and will heat all the rads sufficiently. Range rating helps the boiler perform better by capping its maximum on first fire but not doing it will not cause any problems.

 

[Boilerman2]

What the F**K has boiler output got to do with it the OP took out a 19Kw boiler and replaced it with a 6-31Kw FULLY MODULATING unit so lets start looking at system circulation perleese

 

[mickyg]

What the F**K has boiler output got to do with it the OP took out a 19Kw boiler and replaced it with a 6-31Kw FULLY MODULATING unit so lets start looking at system circulation perleese

calm down dear. Hopefully my explanation will help our bookworm friend mr hailsham. I think its pretty clear there's an issue with balancing or circulation to everyone who actually works in the industry

 

[Boilerman2]

That's the problem with wannabee's trying to answer OPs it just muddies the water so to speak

 

[D_Hailsham]

Range rating helps the boiler perform better by capping its maximum on first fire but not doing it will not cause any problems.

You have hit the nail on the head; it's all about the first fire. The problem is that every time the boiler restarts it is treated as a first fire so, if the water gets heated up faster than the rads can dissipate the heat, the water temperature will rise to quickly and the boiler thermostat will kick in.

If you don't think this will cause any problems, there are plenty of cases on here where the problem was resolved by capping the maximum output of the boiler.

 

[Boilerman2]

You clearly have no idea about the workings of an intelliegnt pre-mix burner as used on vaillant and other boilers if the water in the boiler was rising rapidly, the boiler would modulate down, if when modulated the heat was still not dissapating then the CIRCULATION OF THE SYSTEM IS IN SERIOUS DOUBT and that my friend is the CRUX of the problem of course by now your insane ramblings will have confused the OP beyond belief

 

[Biggles..]

i only mentioned it in the first instance because as the installer did such a good job of powerflush,ph test,balancing i was worried that he could actually have rated it lower than required causeing constant firing and low temp.

I'll stick with my very first post and still say balancing issue as the boiler and pump are more than capable.

BM2 the boiler isnt 6-31 for central heating

lee

 

[sambotc]

Not on an ecotec

My heat output equals about 8kw and I have/had no problems using factory setting (MAX@24kw)

The boiler will recognise a sharp temp increase and adjust accordingly.

Check my post on page 1, it's in black and white direct from the MI.

Sam

 

[D_Hailsham]

an intelligent pre-mix burner as used on vaillant and other boilers if the water in the boiler was rising rapidly, the boiler would modulate down,

Now who's talking theory? I don't know what the reaction time of the typical modulating burner is, but I bet it's not instantaneous - after all it is a mechanical device.

If you have a 30kW boiler and only 15kW of rads, the water temperature will rise very quickly, irrespective of how good the circulation is.

My heat output equals about 8kw and I have/had no problems using factory setting (MAX@24kw)

But is it modulating down to 8kw or continually cycling?

 

[sambotc]

It modulates down when it gets a return temp higher/quicker than it would expect at full output. As far as I know it can then calculate what output matches the rate at which the return temp is rising towards max temp and choose the correct output to suit. Someone correct me there if i'm wrong.

The boiler does not cut in and out unless it is the CM927 telling it to do so, all my rad's get hot at the same rate because there is sufficent circulation to do so.

I really can't see how your theory makes sense? If the output was to high, what would stop the downstairs radiators getting hot? The pump is still circulating so if the pipework to said radiators is unobstructed what is the cause?

Just incase you missed it the first time:

Untitled

• sambotc
• 7 Mar 2010
• 1

Sam

 

[Agile]

The boiler does not cut in and out unless it is the CM927 telling it to do so, all my rad's get hot at the same rate because there is sufficent circulation to do so.

Sam

I think that you may be crediting the boiler with rather more intelligence than it actually has!

In your case I am sure your rads are well balanced and so the system performs as expected.

Just imagine for a moment that the OP's rads are not balanced and just one is wide open and returns hot water to the return. The boiler will rapidly shut down. Even more rapidly if not range rated.

I agree the underlying fault is the lack of balance but range rating the boiler will keep it on for longer.

So it needs range rating as well as balancing.

Furthermore range rating will increase efficiency by condensing more.

Tony

 

[sambotc]

But the boiler does this automatically.

The root cause is the circulation, why range rate the ****ing thing to suit the upstairs working only?

I've just watched my boiler operate (I know, but the misses has dancing on ice on the TV, so this seemed like good entertainment in comparison)

The boiler fires on full for 5 seconds, the return temp is obviously high as the heating has been on all night. The boiler then drops right back to low and slowly ramps up again as it calculates what is necessary to match flow with output.

 

[goon3r]

So...ive just got in from a nice sunday meal and beer with the missus to find world war 3 on my original post!! calm down boys.... were all friends here


To answer some of earlier questions
- Yes, downstairs rads are drop fed despite boiler now being placed downstairs.
- Is it microbore pipework - not a clue mate
- Mr Hailsham... There obviously isnt a TRV on the rad where the thermostat is located. schoolboy error isnt that one? The CH output wasnt taken into account as i was told the boiler was more than capable of coping with size of house. I called the gassafe engineer today and he told me he actually balanced system to try to address issue. The boiler doesnt seem to be cycling exactly as you say. It fires up to the temp displayed on the boiler, cuts out when it reaches that temperature then only comes back on when temp drops significantly.

Let me give you all the latest

I turned on system whilst i went out and turned down all rads upstairs via the TRV's. When i came back the Rads downstairs are all getting much warmer (fully opened) but not with the intensity of upstairs rads. seems with prolonged usage it is getting better but the issue is still there. Im guessing as said many times earlier this points to a balancing problem.

Lastly - Can i close book on rating the boiler? seems like it isnt required?