Gas Rate - Combi

[bwel]

Just checked the Gas Rate on my boilers in a) House and b) Annex. The House is a System Boiler and Annex is a Combi,

I've checked them both on CH over 120 sec, and I know I need to do the Combi with HW demand rather than CH, but came out with a high value on the Combi CH so I'm booking in a service.

The results are:
House (System Boiler) - Vaillant ecoTEC plus 630 (30kw)
- 6.01kw Gross

Annex (Combi) albeit set to CH demand for Gas rate test. - Vaillant TURBOmax Plus 828 E - (28kW)
- 20.17kW Gross

In both cases I did a few Gas Rate samples, but have taken the average of each boiler for the above.
The House Boiler definitely modulates and to be fair, had been on so return flow was already pretty high, and I think I recall the display showing a high modulation on the bar graph.

The Annex - TURBOmax 828, is not very sophisticated and does not give any feedback on modulation level. Equally, I think that boiler modulates after 2 min or so , so would not apply within the first 2min of gas rate test. Either way, it seems the 1 room, 3 rad Annex is a lot higher than my house that is much bigger.

I'll be informing the Gas eng of what my observations are, so he definitely checks the gas rate in the service, but I'm wondering if anybody would be concerned with the Annex Combi Gas Rate of 20kw with CH demand ? perhaps I'm being over cautious, but don’t want to be burning extra gas or ignoring a problem, so thought its worth having an additional service call even if its not due.

 

[Harry Bloomfield]

The House Boiler definitely modulates and to be fair, had been on so return flow was already pretty high, and I think I recall the display showing a high modulation on the bar graph.

Does the above paragraph not explain why there was such a big difference in instantaneous consumption?

 

[Johntheo5]

Combis have a lower output on CH vs HW, it should be in the instructions.

 

[FiremanT]

Just checked the Gas Rate on my boilers in a) House and b) Annex. The House is a System Boiler and Annex is a Combi,

I've checked them both on CH over 120 sec, and I know I need to do the Combi with HW demand rather than CH, but came out with a high value on the Combi CH so I'm booking in a service.

The results are:
House (System Boiler) - Vaillant ecoTEC plus 630 (30kw)
- 6.01kw Gross

Annex (Combi) albeit set to CH demand for Gas rate test. - Vaillant TURBOmax Plus 828 E - (28kW)
- 20.17kW Gross

In both cases I did a few Gas Rate samples, but have taken the average of each boiler for the above.
The House Boiler definitely modulates and to be fair, had been on so return flow was already pretty high, and I think I recall the display showing a high modulation on the bar graph.

The Annex - TURBOmax 828, is not very sophisticated and does not give any feedback on modulation level. Equally, I think that boiler modulates after 2 min or so , so would not apply within the first 2min of gas rate test. Either way, it seems the 1 room, 3 rad Annex is a lot higher than my house that is much bigger.

I'll be informing the Gas eng of what my observations are, so he definitely checks the gas rate in the service, but I'm wondering if anybody would be concerned with the Annex Combi Gas Rate of 20kw with CH demand ? perhaps I'm being over cautious, but don’t want to be burning extra gas or ignoring a problem, so thought its worth having an additional service call even if its not due.

The RGI will not be interested in your figures as they were not derived from a correct test. So are meaningless.
What makes you think a rate of 20.17Kw (although, in fact, a miscalculation) on a 28Kw boiler is high?

 

[bwel]

The RGI will not be interested in your figures as they were not derived from a correct test. So are meaningless.
What makes you think a rate of 20.17Kw (although, in fact, a miscalculation) on a 28Kw boiler is high?

The Engineer is only being called to check out the combi boiler is working properly and not over consuming gas. To be fair if it is consuming 20kw to feed 3kw of radiators do you think I am being over cautious ?

 

[bwel]

Does the above paragraph not explain why there was such a big difference in instantaneous consumption?

I have no concerns on the house boiler modulating, it was just a comparison.

The annex only has 3kw if radiators that were also warm at the time of the test. I’m just thinking 20kw of gas consumption to circulate through 3kw of radiators in a one room annex appeared very high.

 

[Madrab]

Without wishing to sound patronising but I think your understanding of how these systems work and how they would be tested/gas rated properly unfortunately isn't correct. The boiler needs to be run in a specific way under certain conditions to gas rate them correctly.

If you at all concerned then by all means get someone it to check them but as far as gas rates etc are concerned but I'd leave it to the GSR engineer to do all of that.

 

[bwel]

The RGI will not be interested in your figures as they were not derived from a correct test. So are meaningless.
What makes you think a rate of 20.17Kw (although, in fact, a miscalculation) on a 28Kw boiler is high?

It was just a question rather than a conclusion.

Given the Annex 2 min gas rate test was done on CH with the warm 3 rads, rather than in the DHW which would be expected to run at full rate, this raised my question in thoughts on getting an engineer in.

Are you rather thinking that the question was not really something I should be sufficiently concerned about ?

 

[roguetrader]

The Internet....
Has a lot to answer for.