I'm trying to model a heat recovery device on a 100% OA VAV unit. The
supply air temperature setpoint is a constant 55 F throughout the year. To
maximize the savings, we will be locking out the heat recovery when the
outside air is between 55 and 72 F. When the outside drybulb is less than
55, we will have pre/re-heat savings, and when the outside drybulb is
greater than 72 we will have sensible cooling savings. The closest control
scheme that I can find to this in eQuest is to set ERV-RUN-CTRL = "OA
Exhaust DT", set ERV-RECOVER-MODE = "OA Cooling" and OA-EXHAUST-DT = 0.
But unfortunately, this will not pick up the heating savings.
Does anyone know of a better way to model this control?
Aaron
One way to do it would be to build a custom 8760h schedule using the schedule excel tool produced by EMIT (attached).
You output the outside temp of your meteo file and manually set them to On/Off according to the outside temps you mentionned below (0 between 55 and 72, 1 otherwise).
Then you import the schedule in your model and set your ERV to run according to this schedule.
It?s a little longer but it will do exactly what you want to.
[Bouthillette Parizeau]
Patrick Lapierre_ing.
plapierre at bpa.ca
De : Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] De la part de Aaron Powers
Envoy? : 14 mars 2016 12:56
? : equest-users at lists.onebuilding.org
Objet : [Equest-users] Heat Recovery Control
I'm trying to model a heat recovery device on a 100% OA VAV unit. The supply air temperature setpoint is a constant 55 F throughout the year. To maximize the savings, we will be locking out the heat recovery when the outside air is between 55 and 72 F. When the outside drybulb is less than 55, we will have pre/re-heat savings, and when the outside drybulb is greater than 72 we will have sensible cooling savings. The closest control scheme that I can find to this in eQuest is to set ERV-RUN-CTRL = "OA Exhaust DT", set ERV-RECOVER-MODE = "OA Cooling" and OA-EXHAUST-DT = 0. But unfortunately, this will not pick up the heating savings.
Does anyone know of a better way to model this control?
Aaron
I did exactly this for a recent job for the same reasons (lockouts between setpoints for heat recovery operation).
The only extra caution is ? this is actually very easy to do, but be mindful you?ll end up adding approximately 400 components to your model after import (between the day/week/annual schedules). If your model is already in or certain to reach ?overweight? territory in terms of loading/simulation times, it may be advisable to push this towards the end of your to-do list for model development (if feasible).
If you want to more quickly/lightly approximate the savings for all seasons, you could run an hourly of your exhaust air temps at the heat recovery to come up with an annual median, then consider that exhaust temperature in relation to your 55/72 ?lockout targets? to come up with an ?averaged absolute annual differential? to use in combination with ERV-RECOVER-MODE = OA-HEAT/COOL. This will deliberately overstate cooling recovery + understate heating recovery operation (or vice versa), but would hopefully ballpark what?s happening on an annual savings basis well enough.
You could also ?tune? the ?light? approach to adjust the delta input in combination with a model fork using the ?imported spoon-fed operation? approach (you may want to develop that schedule anyway for eventual import/use, so it wouldn?t be wasted time), but again I?d probably be inclined to ultimately land on that more ?locked in? solution and just plan my model development around doing that last or towards the end.
~Nick
---------------------------------------------------------------------------------------------------------------------------------------------
Nick Caton, P.E.
Senior Energy Engineer
Energy and Sustainability Services
North America Operations
Schneider Electric
D 913.564.6361
M 785.410.3317
E nicholas.caton at schneider-electric.com
F 913.564.6380
15200 Santa Fe Trail Drive
Suite 204
Lenexa, KS 66219
United States
*Please consider the environment before printing this e-mail
Thanks Nick and Patrick. Those are two much better options. Now I'm
curious to see what effect the 8760 schedule will have on performance since
I've always tried to stay clear of this method. Right now I have about
3500 components in the model, so adding another 52 + 365 components should
be relatively tolerable in terms of load time. I'd also like to see what
the effect on simulation time will be. The biggest drawback for me is that
the schedules section of the Component Tree will become very bloated and
possible un-navigatable, so I can see why this might need to wait until the
end.
It just occurred to me that I could also run 2 separate parametric runs:
one which locks out above the exhaust air temperature (72) and the other
that locks out 17 degrees below the exhaust temperature (55). I would
think the results should be additive.
Aaron
I don?t believe I?ve subjectively noticed a substantial effect on simulation times to worry about, but the real rub is in extra loading & BDL initialization time within the eQuest interface during simulation/parametric runs. (Possibly an important distinction for those of us tinkering with command-line doe2 applications.)
I also don?t believe I?ve ever ?broken? the component tree in length, though I wouldn?t put it past Aaron to find/share such a limit if it exists (& I mean that as a compliment)! Following EMIT-imported schedules, you?ll note schedules are handily always the last category under each tab?s component tree so other things aren?t pushed far out of view, and the consistent naming EMIT spits out makes those numerous week / day schedules pretty easy to distinguish from any named scheduling before/after import.
I have a hunch however since we?re talking about navigation pitfalls: it?s probable loading the spreadsheet view for day schedules will give eQuest a heart-attack if you import such schedules a few times over for one project ;-)!
~Nick
---------------------------------------------------------------------------------------------------------------------------------------------
Nick Caton, P.E.
Senior Energy Engineer
Energy and Sustainability Services
North America Operations
Schneider Electric
D 913.564.6361
M 785.410.3317
E nicholas.caton at schneider-electric.com
F 913.564.6380
15200 Santa Fe Trail Drive
Suite 204
Lenexa, KS 66219
United States
*Please consider the environment before printing this e-mail