[Bldg-sim] Energy efficieny: VRF + DOAS vs VRF + unconditioned Ventilation system
andrew.corney at sefaira.com
Tue Jul 21 08:32:01 PDT 2015
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
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>
> 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> 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
>> 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!
>> On Tue, Jul 21, 2015 at 2:33 PM, Santiago Velez <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.
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>> Andrew Corney
>> PE M.CIBSE M.ASHRAE
>> Product Manager - Sefaira Systems
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PE M.CIBSE M.ASHRAE
Product Manager - Sefaira Systems
Mobile: +44 (0)7887 059 722
Office: +44 (0)2037 147 619
Sefaira - Sustainability. Performance. Design.
*For company contact and registration information, please
*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.*
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