IES-VE User Forum

Can someone please explain the difference between apachesim boiler load and boiler energy. I assume boiler loads are the heating plant sensible load x boiler efficiency. however, what is the boiler energy? i would have thought this was the same but the figure is actual higher than the boiler load. can anyone explain.

Mark

I believe the boiler load is the heat load that the boiler "sees", ie, the base demands plus the system losses associated with delivering heat to those end uses. The boiler energy is then derived by dividing by that load by the boiler's efficiency.

This is just my understanding and I welcome any further comments who may want to agree/disagree. Also, the Vista help file defines the variables so it may be worth a look.

Yep, got that and I see how it calculates boiler load and boiler energy. However, how does this relate to heating sensible load. If I have this how can I relate this to energy. I assumed that it is heating sensible loads x boiler efficacy would equate to boiler energy. But this doesn't quite work out this way.

Ok, here's an example:

Boiler Seasonal Efficiency - 0.9
System Delivery Efficiency - 0.85
SCoP = 0.9 x 0.85 = 0.765

Total Rooms Sensible Heating Load = 50kW
Aux Vent Heating Load = 150kW

Total Sensible Heating Load = 50+150 = 200kW

Boiler Load = Total Sensible Heating Load / System Delivery Efficiency = 200/0.85 = 235.3kW

Boiler Energy = Boiler Load / Boiler Seasonal Efficiency = 235.3/0.9 = 261.4kW

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The above is how it should work but it can sometimes be difficult to break it into those exact parts if you have multiple systems. Also, the aux vent load does not show up inside the room variables view and so is easily missed if applicable.

Thanks.