Vaillant Sustain 28kw Combi Heat Input

richard978 · Jun 24, 2024

Could anyone tell me whether the Vaillant Sustain heat input is noted in gross or net please.

I was sure it was NET but someone has said it's gross which makes no sense at all. I work all my gas rates to NET so if I'm wrong my gas rates will be way out.

I've included the data badge.

ShaunCorbs · Jun 24, 2024

Will be Net as it would be a 25kw combi

richard978 · Jun 24, 2024

That's what I thought because it would not be a 28kw boiler now days with a gross figure. I was worried I'd got my figures all wrong.....

John.g · Jun 25, 2024

richard978 said:
That's what I thought because it would not be a 28kw boiler now days with a gross figure. I was worried I'd got my figures all wrong.....

If you mean the fuel input then that is the gross heating value, that's what you are paying for.
Yours, I think is a "28kw" and is limited to give 18.5kw to 20.1kw output to CH but gives 28kw output to HW (combi mode), it gives a DHW flowrate of 11.6LPm @ a dT of 35C which equals a output of 28.33kw, the fuel input, depending on whether partially condensing or not, probably not in DHW combi mode, might be ~ 32/33kw or approx 2.9/3.0m3/hr of N.gas. The sustain apparently gives the same CH output in the 24kw, the 28kw & the 34kw models but gives DHW outputs of 24.4kw, 28.5kw & 34.6kw.

Vaillant Sustain 28kw Combi Heat Input

richard978

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