[Bldg-sim] Energy efficieny: VRF + DOAS vs VRF + unconditioned Ventilation system

[Duggin, Cory]

It’s also worth noting that VRF FCU typically don’t have a lot of latent capacity, so they can only handle a limited amount of OA within a certain envelope.  There are VRF DOAS FCU that are designed to handle OA though.  These can be used if  you want to take advantage of heat recovery from the ventilation load.

Cory Duggin, PE, LEED AP BD+C
Associate/Energy Engineer
TLC Engineering for Architecture
direct:

615-346-1939



From: Bldg-sim [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Andrew Corney
Sent: Tuesday, July 21, 2015 10:32 AM
To: Santiago Velez <santiagogvelez at gmail.com>
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Energy efficieny: VRF + DOAS vs VRF + unconditioned Ventilation system

Hmm. Not sure but it seems likely that a wet coil could affect the efficiency performance of the VRF FCU.

From an energy perspective heat recovery centrally could be made to be very efficient. If you bring air in from outside and let the VRF system see it then you might not get those benefits and the ventilation load might be a lot higher. This could be offset for heating with a zone by zone MVHR system.

That said you could potentially have latent heat recovery at a central AHU where it would be very hard in an MVHR ventilation unit. In more extreme climates this could make a substantial difference. For example this could help rehumidify the air in very cold places or dehumidify the air in hot humid climates. The heat recovery would then be a direct saving against the coil load (although it would increase pressure drop in the DOAS system!).

On Tue, Jul 21, 2015 at 4:06 PM, Santiago Velez <santiagogvelez at gmail.com<mailto:santiagogvelez at gmail.com>> wrote:
Thanks Andrew, I wonder though if besides first cost or maintenance related issues there are any energy savings at all, and if so why is that the case. I Read about better performance of evaporator running with lower air temperature in a DOAS, but you still need energy to treat ventilation air in the DOAS system, so were are the savings coming from?



On 21 July 2015 at 10:39, Andrew Corney <andrew.corney at sefaira.com<mailto:andrew.corney at sefaira.com>> wrote:
Hi Santiago,

One benefit might be the ability to do the dehumidification remotely via the DOAS system. This could alleviate the maintenance of drip trays / condensate drains from your VRF fan coil units. You might also be able to down-spec the VRF fan coils that you are using as well (possibly reducing size).

Another benefit would be that it might be cheaper to do a higher performance style of heat recovery centrally that could help reduce heating energy in particular.

So there are 2 reasons!

cheers,

Andrew

On Tue, Jul 21, 2015 at 2:33 PM, Santiago Velez <santiagogvelez at gmail.com<mailto:santiagogvelez at gmail.com>> wrote:
Dear Group, Can someone enlighten me about the energy efficiency benefits of conditioning the ventilation air in a VRF + DOAS system, versus letting the VRF handle all the load (internal loads + Ventilation loads).
Thanks in advance.
Regards,
Santiago.

_______________________________________________
Bldg-sim mailing list
http://lists.onebuilding.org/listinfo.cgi/bldg-sim-onebuilding.org
To unsubscribe from this mailing list send  a blank message to BLDG-SIM-UNSUBSCRIBE at ONEBUILDING.ORG<mailto:BLDG-SIM-UNSUBSCRIBE at ONEBUILDING.ORG>



--
Andrew Corney
PE M.CIBSE M.ASHRAE
Product Manager - Sefaira Systems

Mobile: +44 (0)7887 059 722<tel:%2B44%20%280%297887%20059%20722>
Office: +44 (0)2037 147 619<tel:%2B44%20%280%292037%20147%20619>
Skype: andrew.corney.sefaira

Sefaira - Sustainability. Performance. Design.

For company contact and registration information, please visit: http://www.sefaira.com/info/contact

Check out our latest webinar showcasing the product here<https://vimeo.com/130461932>. Subscribe here<http://www.sefaira.com/subscribe-from-email/> to our bi-weekly newsletter.




--
Andrew Corney
PE M.CIBSE M.ASHRAE
Product Manager - Sefaira Systems

Mobile: +44 (0)7887 059 722
Office: +44 (0)2037 147 619
Skype: andrew.corney.sefaira

Sefaira - Sustainability. Performance. Design.

For company contact and registration information, please visit: http://www.sefaira.com/info/contact

Check out our latest webinar showcasing the product here<https://vimeo.com/130461932>. Subscribe here<http://www.sefaira.com/subscribe-from-email/> to our bi-weekly newsletter.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/attachments/20150727/04d1d0f2/attachment-0001.html>