Applying SFPs correctly

[Collie]

Hi,

When applying SFPs at system level, is that sufficient for IES to include it in the PArt L calc?
I always assumed it was but I recently QA'd a modelling report and found on the BRUKL that SFPs had been applied for every room at room level. They show up as local supply & exhaust on the document.

Slightly confused now, have I been doing it wrong? eek!

C

[PCully]

This isn't my strongest area I'm afraid but there is a bit on the Knowledge Base here http://www.iesve.com/support/knowledgebase/faq/2729

Have you sat our training recently? I'd expect in either the SBEM or ApacheSim Part L2 2010 training this topic would be covered as well.

Phil

[Collie]

Hi Phil,

Cheers, for that. If I understand that link correctly, it would appear my method in this instance is correct.
However, I'm afraid I've not done any IES training since Uni

[Jonnymac]

Hi

I have read the knowledge base FAQ.

I assume that if you set an SFP at system level, it does not appear on the SBEM BRUKL output document, why is this?

If you set the sfp at system level and have assigned that system to a particular zone, why does IES let you enter a zone level SFP and does this effectively increase the energy?

Also if you set the sfp at system level, does this account for the extract, again this does not appear on the SBEM BRUKL output document. Assuming that the SFP should take into account the supply and extract power, I take it the sfp for the exhaust isn't required if the exhaust is integral to the AHU and not a separate local exhaust fan.

[Collie]

Hi Johnny,

In my limited experience I've found that inputting the SFP at system level should register on the BRUKL providing you've selected mechanilcal ventilation system as the 'primary system'. This figure as I understand it, is a figure for the total system, (Supply & Return) so there should be no need to go to room level and input a local supply or exhaust unless they're present.

If you DO input an SFP at room level, it should register on the BRUKL too under the 'local mecahnical supply & exhaust' section just after the main systems breakdon section, (Page 3 maybe). If you enter a SFP AND a flow rate for the exhaust, this doesn't register on the BRUKL for some reason, I don't know why. When I've done this and queried the relevant rooms in Vista, the system is taking account of the vent so it is in there somewhere. More clarity required though definintely

Let me know if you find anymore out about this as it seems to be widely misunderstood and gets numerous different responses when I ask people about it.

Cheers,

C

[Complex Potential]

If the room is heated or cooled via the ventilation system then the appropriate system type should be selected (for example, a VAV or CAV system) and then the SFP must be defined within the system tab.

If the room has radiators, underfloor heating or some other local heat source with the mechanical vent only being used for fresh air then the SFPs should be defined at room level. You need to select the NCM radiator system type in such a case and then you will find the SFP box under system adjustment greyed out which will mean you have to input at room level.

The only slight oddity is the FCU system whereby the central AHU SFP must be entered via the main system tab but then the local terminal unit SFP must be entered at room level under the supply side.

If you have input at room level the SFPs will be displayed per room on the BRUKL I think.

CP

[RossThompson87]

Hi,

The IES FAQ does seem to explain it clearly.

However I think in this case the methodology is very harsh when using zone level SFPs.

When you study the behavior of the notional building it applies an SFP of 1.8 W/l/s for central systems, but just 0.9 W/l/s for the zone level.

I think this factor of two difference is where the confusion arrives over putting the full SFP or just that for the supply fan.

It seems almost impossible to find an AHU on the market that gets anywhere near a (full) SFP of 0.9 W/l/s, unless it is hugely oversized. Is there any way we can get in touch with BRE to get confirmation of why this figure is used? I have tried in the past with little success.

Ross

[Complex Potential]

Hi,

The IES FAQ does seem to explain it clearly.

However I think in this case the methodology is very harsh when using zone level SFPs.

When you study the behavior of the notional building it applies an SFP of 1.8 W/l/s for central systems, but just 0.9 W/l/s for the zone level.

I think this factor of two difference is where the confusion arrives over putting the full SFP or just that for the supply fan.

It seems almost impossible to find an AHU on the market that gets anywhere near a (full) SFP of 0.9 W/l/s, unless it is hugely oversized. Is there any way we can get in touch with BRE to get confirmation of why this figure is used? I have tried in the past with little success.
Ross

Ross

I have looked into this exact issue and have posted about it at length over here:

viewtopic.php?f=244&t=3823&p=9047&sid=c ... 96bf#p9047

I have included an update with a response I got from IES about my question but I would be very interested to hear your thoughts.

CP