ecoFIT pure 830 temperature control

[Wibbly]

I have chosen to set the CH temp to 63, but often find the water temp is displayed as high as 66, even when heat is staill being called for. Is this to be expected/normal?

 

[Deleted member 120897]

Quite possibly pump overrun?

 

[Wibbly]

Could be, but it's a modulating boiler and CH is still calling for heat. It's as if it can't control the temp well.

 

[John.g]

I have chosen to set the CH temp to 63, but often find the water temp is displayed as high as 66, even when heat is staill being called for. Is this to be expected/normal?

The displayed temperature is often taken from the cylinder top whereas the cylinder stat is installed ~ 1/4 the way up the cylinder, this is to start heating the water as soon as a relatively small volume is drawn off, say 30/50 litres. The coil is heating from the top down so your stat might call for heat at (63-5) 58C even though the cylinder top is slill at 63C and by the time the stat is satisfied again at 63C then the cylinder top wil be higher, in your case by 3C, 66C.
I use a spare contact on my solar controller + PT1000 (very accurate) sensors to open/close the coil motorized valve at 55/60C, the sensor temperature is exactly60C at shut off but the cylinder top varies between 62/64C depending on hot water drawoff.
Probably if the circulation through the coil was from the bottom to the top then there may be little or no variation?.

 

[John.g]

Sorry, misread you post, forget above.

The boiler should maintain the SP but will only do this if its minimum output is > the CH demand, if not, then it will continue to rise to normally SP+5C so will then cut out if it reaches 68C in your case

 

[Deleted member 120897]

If it’s relatively new, the link may have been left in.

 

[Timmy D]

If it’s relatively new, the link may have been left in.

I don’t think the issue is with the boiler on constantly (link could be correct for this problem), but with the boiler temp over shooting the set flow temp.

 

[Deleted member 120897]

I don’t think the issue is with the boiler on constantly (link could be correct for this problem), but with the boiler temp over shooting the set flow temp.

Thanks, I was going off the curve ball of

Could be, but it's a modulating boiler and CH is still calling for heat. It's as if it can't control the temp well.

 

[John.g]

I don’t think the issue is with the boiler on constantly (link could be correct for this problem), but with the boiler temp over shooting the set flow temp.

So shouldn't stop the burner firing at SP temperature or it is and just going overtemp a little after burner shutdown?

 

[Timmy D]

So shouldn't stop the burner firing at SP temperature or it is and just going overtemp a little after burner shutdown?

I’m unsure.

We need more info really.

TBH, without other problems, I probably wouldn’t spend anytime fixing what is pretty much a non issue.

 

[John.g]

I wouldn't be too happy with that, especially in the summer with no demand for CH and boiler firing constantly on/off on its own stat, there may well be a wire coming from the programmer to the boiler link via the roostats and Mot. valves and just remove the link and insert in the 0V terminal at the boiler.?., like this one in a recent thread.

 

[Wibbly]

I’m unsure.

We need more info really.

TBH, without other problems, I probably wouldn’t spend anytime fixing what is pretty much a non issue.

The boiler shuts down when the stat no longer calls for heat. It occurs when the house is below the house/stat SP but the boiler water temp rises above the boiler's SP for water temp.

@John.g 's explanation above sounds reasonable "The boiler should maintain the SP but will only do this if its minimum output is > the CH demand, if not, then it will continue to rise to normally SP+5C so will then cut out if it reaches 68C in your case". But this is supposed to be a modulating boiler and the radiators are still hot when this happens, suggesting heat output and demand from the boiler is still quite high. Difficult to tell to be honest...

As you say though, if it's not considered broke no point in trying to fix it. I suppose the slightly higher running temp is not materially going to affect its efficiency re condensating?

 

[Deleted member 123817]

I mightn't, have worded that quite correctly but. If the rads heat demand is say 4kw and the boiler min output is 5 kw then the boiler temp will continue to rise until SP+5C , the burner will then cut out, the pump should continue to run the burner will then refire after the anti cycle time has elapsed and the cycle is repeated

 

[Wibbly]

I mightn't, have worded that quite correctly but. If the rads heat demand is say 4kw and the boiler min output is 5 kw then the boiler temp will continue to rise until SP+5C , the burner will then cut out, the pump should continue to run the burner will then refire after the anti cycle time has elapsed and the cycle is repeated

Yeah and it's all subjective, sadly. With many rads as hot as ever to the touch, it 'feels' like the boiler should be working hard, but perhaps not. Will keep an eye on it. Thanks all for the responses, appreciated.

I also bunged a mail to Vaillant. Will update here if there's any/different conclusion.

 

[John.g]

Your's seems to have a relatively high minimum output of 6.3kw so will definitely cycle IMO during times of low demand with mild weather conditions.

 

[Wibbly]

So another short and to the to the point response from Vaillant... "The temperature on the boiler display is the temperature of the main heat exchanger."

So I guess the implication is that is not, necessarily, that representative of the water temp anyway.

 

[John.g]

I would think that (Vaillant) is correct, its the temperature of the water leaving the (main) heat exchanger, also known as the boiler flow temperature or just boiler temperature and the boiler display should show just that.