[Bldg-sim] Domestic Hot Water Heaters With VRF

[Nicholas Caton]

Interesting idea!



Whatever simulation package you choose to leverage, I think you may
anticipate blazing a new trail to some extent.  I am unaware of any
purpose-built tools for simulating the specific task at hand.  If anyone
*would* know of such tools, it might be the R&D departments for
manufacturers pushing such combination systems
(Toshiba/Mitsubishi/others?).  If time is on your side, sending a query up
the manufacturer chain might be worth your while.



At present, if you should opt to utilize eQuest/DOE2 for your study, VRF
with heat recovery function (“free heating/cooling” via zonal transfer) can
be *approximated* via post-processing of the hourly outputs.  Having tread
this path a number of times for different building types and having studied
various published/unpublished guidance for such procedures (one can source
such guidance in attachments within the [equest-users] archives), what
you’re considering exploring with DHW could be relatively simply layered
into the post-processing efforts with a small set of extra assumptions (and
a fair effort to accurately schedule/quantify DHW loads within the
simulation).  I’d want to get all the cutsheets in front of me and to have
the equipment rep(s) for the basis of design at-hand to ensure appropriate
safety factors and assumptions of system behavior are addressed at the
outset of the study.



Agnostic to your simulation package preferences/decision:  Thinking out
loud and considering how the potential for savings may inverse with the
season, especially for a climate like KS where the seasonal swings are
sustained and pronounced, it would be worthwhile to establish whether the
SHW/VRF systems might be “de-coupled” on a simple-seasonal or monitored
basis in a cost-effective / low-maintenance / buildable fashion.  If
feasible, I would plan to include quantifying the associated annual savings
potential for a simple ROI check with your results.



Let us know how it goes!



~Nick



*NICK CATON, P.E.*
*Owner*



*Caton Energy Consulting*
  1150 N. 192nd St., #4-202

  Shoreline, WA 98133
  office:  785.410.3317

www.catonenergy.com



*From:* Bldg-sim [mailto:bldg-sim-bounces at lists.onebuilding.org] *On Behalf
Of *Jim Dirkes
*Sent:* Thursday, May 07, 2015 12:26 PM
*To:* Hollon, Ben
*Cc:* bldg-sim at lists.onebuilding.org
*Subject:* Re: [Bldg-sim] Domestic Hot Water Heaters With VRF



I haven't done this yet, but.....

   - The VRF object in EnergyPlus allows a water-cooled condenser.  I
   suspect you could connect that water loop to a water heater without
   difficulty and adjust the water loop pump power to zero, etc.  The E+ water
   heater allows two energy sources (water and gas, for example) so when
   winter rolls around, the gas can take over ... or something like that.
   - I have modeled VRF (prior to E+ having the capability) as a
   water-source heat pump system.  The condenser loop could pass through a
   water heater or heat exchanger and accomplish your goal. (If you use this
   approach, the heat pump COP must be very high so compressor power is
   ~zero.  The condenser loop chiller / heater must have efficiency curves
   that are similar to the VRF system)



On Thu, May 7, 2015 at 3:11 PM, Hollon, Ben <bhollon at antella-inc.com> wrote:

Hi,



Has anyone ever had any experience with modeling a VRF system with
individual hot water heaters tied into the refrigerant loop?



We are debating in the office how this would be handled by an energy
modeling program. In the summer you could produce almost free hot water and
reduce the condensing unit load. But in the winter you would either need
greatly oversized condensing units or auxiliary heat. I'm not aware of this
level of functionality in an energy modeling program with domestic hot
water heating. We are thinking you would need to perform some amount of
calculations by hand with outputs from an energy model...



Also, has anyone had any positive or negative experiences with this in
terms of performance and operations?



Thanks!

<https://ee70db1b-a-1347254f-s-sites.googlegroups.com/a/antella-inc.com/cadstandards/other/Ant-Logo.jpg?attachauth=ANoY7crK3WoX4hU441SAa703fENBeWmmomx2fSEwMugePrx8z8UbHuYup2eh-hLOT4cCifwEfw-EWAzIKfrb50zUwHPiF0KXB-3KyY35c4CKX9033i50232S12FIWzuqbYM-NB1gCHyMd3lWot8TXxqNnFX24oedBXR2aqSvsFkMhpuy3RH-Ue-69vX4glR7HBtQScw8X_R1KwOLH0bh-eu-g2MF1uuWJ-jeHWzdoOweXgOBm4HdSN4%3D&attredirects=0>

*Ben Hollon, EIT, LEED*®* AP BD+C, MBA*

email:  bhollon at antella-inc.com <xxxxxx at antella-inc.com>






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