Questions Regarding SS-N and SS-O Reprts and Unoccupied Heating and Hummidty Requirements

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Everyone, I have an indoor pool in Alaska. I have figured out how to model the pool's 24/7 latent load and required the pool area HVAC system to maintain 88 F even for Night Cycle. I also gave the pool HVAC the task of maintaining 60% max RH. The SS-C report shows the pool HVAC fan running 8747 hours out of the year, 2357 of those hours running during unoccupied hours. This is what I expected. I looked at the SS-O and SS-N reports for my pool area and pool HVAC and noticed that 6390 hours of temperature and relative humidity data are showing up, not 8740 hours. In other words all the 2357 unoccupied hours are not showing up. How do I verify if my pool HVAC system succeeded in managing to keep 88 F and below 60% RH during the unoccupied period? I assume it can manage the temperature problem, but how well did it manage the humidity problem? Or did it just bag the humidity problem, in which case, do I have to run the fan system 24/7 to get it to pay attention to the 60% max RH?
If I have to run the fan system 24/7 will that 0 value in the MinOA WD schedule keep the outside from coming on or do I need to change it to a positive number? If so, which positive number? 999?

Peculiar questions, I know.

Kathryn Kerns's picture
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Pools are interesting to model. We are working on a project right now with one. One challenge we have is how/where to get the heat recovery data from the equipment vendors that sell the systems that can provide condenser heat rejection for use in heating the pool. I'm sure we will figure that out at some point.

For your project, I would recommend creating an hourly report for that zone with zone temp and humidity. Then run eQuest, export hourly report, and then analyze to see what's going on.

Can you please let us know what you find out? The community at large might be interested in knowing.

Here are some "Thermal Zone" variables that might be useful for diagnosing the operation.

[cid:image002.jpg at 01CE3C7F.269DEC00]

Export hourly results:

[cid:image006.jpg at 01CE3C7F.269DEC00]

Regards,

JAH

James Hess's picture
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Everyone, after stumbling around a little, I discovered that
eQuest/DOE-2 does take into account the maximum relative humidity limit
during unoccupied hours and operates the zone HVAC fan energy, cooling
and heating with the OSA closed. I figured this out by running the fan
system 24/7 (it was running 24/7 anyway according to SS-C) and noticing
that the total energy consumption did not change. Humidity and
temperature data then appeared in SS-N and SS-O reports. I also found
some help files that state that 0 in the MinOA schedule means closed OSA
so I know there is no OSA going into the pool area at night. So the
model I had was working fine, I just couldn't prove it. Running the HVAC
system 24/7 proves it.

So, now I am at the point of introducing my dehumidifier system to the
pool zone. I am planning on using the pool PSZ HVAC cooling coil to
represent the dehumidifier cooling coil since the specified PSZ HVAC
does not use a cooling coil. What I would like to do, is decrease the
PSZ SUPPLY-KW/FLOW value during unoccupied hours to represent the lower
dehumidifier fan rate. Does anybody know how to do this? In other words,
I want the pool zone PSZ HVAC supply fan to run at 0.0007 kw/cfm during
the day and run at 0.0003 kw/cfm during unoccupied hours. If I can't
change SUPPLY-KW/FLOW, is there a way to develop a schedule that
DECREASES the electric load by some amount during unoccupied hours? I
have found ways to add a load, but not subtract.

Thanks in advance.

James, I am not sure what you are trying to do? Condenser heat rejection
from what? A water to air heat pump?

Kathryn Kerns

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Kathryn,

I'm not exactly sure what you are trying to model either. But, I think the only way (I can think of) to do what you are mentioning (or close to) is to create a custom fan power curve that provides the fan power values that you expect at the occupied and unoccupied (dehumidifier) airflows. I would then program a minimum airflow schedule that set the minimum airflow at one value during the occupied hours and then switched to a value equal to the dehumidifier airflow during unoccupied periods.

There's no way to add a negative value to a meter. I wish we could. I made that suggestion to the eQuest developers about 5 or 6 years ago, but never heard anything back. I agree it would be a nice option. We could add in solar PV or solar thermal estimates from other programs, for example.

As far as I know, you cannot set the fan kW/CFM value to a schedule.

Switching gears, what we are trying to model is by PoolPAK International, and best described here:

http://www.poolpak.com/index.php/search-product-2/poolpak-model-sr

and here:

http://www.poolpak.com/download/ppk/MK5_EG_PPK_REV-20120612.pdf

Basically, this unit will completely condition both temperature and humidity for the indoor pool environment. This equipment contains a refrigerant to water heat exchanger to preheat the pool water using condenser heat rejection. See the diagrams on page 10 (PDF 14) in the above referenced PDF. This is a good match because the majority of the pool heat loss is due to evaporation. This unit manages the pool room humidity using the refrigeration cycle while recycling condenser heat rejection back into the pool. Pretty cool. I don't think eQuest can model this heat recovery however, or at least I don't know how. We will probably end up with some kind of side exceptional calc based on heat recovery data provided by the mfg (PoolPAK). The idea is that the heat recovery will offset the gas usage of the conventional pool heating boiler, used in the Baseline (and Proposed as supplemental heater).

I was wondering if you were modeling anything like this, since this type of equipment seems standard for indoor pool environments?

Thanks!

Regards,

JAH

James Hess's picture
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James, thanks for the thought about the fan curve. That might do it.
However, I think what I am going to do is split my Natatorium in 2 zones
with a large air wall between the zones. One zone will handle the
outside air HAVC system with OSA requirements, and the other zone will
have no OSA and all of the pool evaporation load. This will solve my
different fan power problem and will represent my proposed system
better.

Your system looks like a heat pump horseshoe where you use the hot gas
to dehumidify and then what ever is left over heats the pool? I think I
have modeled something like this before with a DX coil and a downstream
hot water coil attached to an electric boiler that has a efficiency much
greater than 1, in other words, free, since it represents the hot gas
bypass. You have to make sure the DX coil and boiler sizes match the
horseshoe equipment capabilities. As for adding the pool load, the only
thing I can think to do is put a meter on the boiler and subtract
whatever amount you are using for dehumidification from the maximum
amount the hot gas can produce and say that is how much is available to
heat your pool. Maybe something like that?

Kathryn Kerns

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Kathryn,

10-4, both of your ideas sound like good ideas to me. We will give your recommendation a shot.

If we did as you suggested and sub-metered the reheat HGB/fake boiler output energy, I agree that subtracting this boiler output from the total condenser heat rejection provides a reasonable estimate of the heat recovery available for pool heating. We could do the math on an hourly basis in a spreadsheet and then totalize for the year to get a good estimate for annual pool energy savings. I think that is a good approach.

Thanks! :)

Regards,

JAH

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