'Fabric and Ventilation' output -> "Ex mech vent&

koen.govers · Posts: 80

Hey,

"The zone heat balance" shows all fabric heat gains/losses, but suprisingly not all the ventilation heat losses; it only goes from "Glazing" to "External infiltration".
In 'display options' u can see all these heat gains/losses and 2 additional ones:
- "Ex mech vent" (standard; pink colour) - "Ex nat vent" (standard; dark green).
These options are chosen but somehow the "ex mech vent" isn't shown on the graph although i'm using mechanical ventilation.
Ive tested the output at building and zone level.
If i use 'customisation dialog ...' and go to the 'subsets' tab the options "Ext mech vent" and "Ext nat vent" just aren't there.
So, is this output removed in the recent versions? Or did i miss out on something?

Thanks in advance,
Hans

Laurent_Support · Posts: 292 Location: Vincennes

Hello Hans,

Do you see Air change per hour values under the heat balance graph?

Laurent

koen.govers · Posts: 80

Hey Laurent,

Ye I do see that graph.
But e.g. when I define natural instead of mechanical ventilation, I get that air change graph + in the 'Zone heat balance' "Ex nat vent" is shown.
When using mechanical ventilation, the air change graph is shown, but "Ex mech vent" in the zone heat balance isn't.
I think it's missing because the total 'Zone heat balance' adds nowhere near to zero (i know it doesn't add to zero which is explained in a technical note in help, but only somewhere near to it).
Feel free to correct if I'm seeing this wrong Smile

Well i hope this info helps you to understand what i mean. I've also send the file by mail.

Kind regards,

Hans

Andy Tindale · Posts: 1205 Location: Stroud

The cooling effect of the mechanical ventilation is accounted for in the Zone/Sys Sensible Cooling. This is defined in the documentation as:

... the sensible cooling effect on the zone of any air introduced into the zone through the HVAC system. It includes any 'free cooling' due to introduction of relatively cool outside air and the heating effect of any fans present. Cooling always shows as a negative heat gain in the results. It is therefore not the same as a cooling coil energy delivery when mechanical ventilation is involved. It is best thought of as the HVAC cooling contribution to the zone heat balance.

Regards,

Andy

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