[Equest-users] Modeling Reverse Acting TStat EF
Nicholas Caton via Equest-users
equest-users at lists.onebuilding.org
Wed Oct 19 12:43:45 PDT 2016
Immediate thought: Have you set a cooling thermostat schedule for the zone with 80F at all hours? That would explain both the lack of unmet hours and no calls for conditioning (fan operation).
If there is a thermostat schedule, did you confirm the fan is never operating via custom hourly output reporting? Do you have a system fan schedule forcing OFF behavior with zeroes and/or -1’s? If so, try forcing ON with 1’s and/or just not defining a fan schedule at all to permit system fan operations when called for.
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Nick Caton, P.E., BEMP
Senior Energy Engineer
Energy and Sustainability Services
Schneider Electric
D 913.564.6361
M 785.410.3317
E nicholas.caton at schneider-electric.com<mailto:nicholas.caton at schneider-electric.com>
F 913.564.6380
15200 Santa Fe Trail Drive
Suite 204
Lenexa, KS 66219
United States
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From: Darryl Kasun [mailto:darryl.kasun at gmail.com]
Sent: Wednesday, October 19, 2016 1:18 PM
To: Nicholas Caton <Nicholas.Caton at schneider-electric.com>
Cc: Brian Fountain <bfountain at greensim.com>; Julien MARREC <julien.marrec at gmail.com>; equest-users <equest-users at lists.onebuilding.org>
Subject: Re: [Equest-users] Modeling Reverse Acting TStat EF
Hi everyone,
Thanks again for all your input.
I've run into a snag. I cannot seem to get the fan to turn on when the temp > 80 degF. When I look at some of the reports I see that there is no reported unmet clg hours for this zone which is a red flag - not sure why this is. There is a sizable clg load in this zone: 65 MBH. I do see on the SS-F that the max zone temp hits 86.1 degF. Any thoughts?
On Tue, Oct 18, 2016 at 4:00 PM, Nicholas Caton <Nicholas.Caton at schneider-electric.com<mailto:Nicholas.Caton at schneider-electric.com>> wrote:
Hey Darryl,
This turned into a big response, but it seems the problem we’re trying to help solve is a moving target!
1. The advice to enter something nominal but tiny for cooling capacity, to avoid autosizing & prevent airstream cooling, is based on the earlier statement that you do not intend to cool the airstream making up the exhaust. Going the other route of just making it “free cooling” (EIR=0) goes against your goal of modeling reality as now the exhaust “makeup” airstream is being conditioned on its way in, resulting in milder interior temperatures for determining hourly zonal heat transfers. An equally viable alternative I generally prefer to “lock out” cooling operations by the way is an airside system COOLING-SCHEDULE with hourly values of zero. An expected side effect of of crippling/breaking your PSZ’s cooling capacity with a tiny number is that you will end up with a justifiable quantity of unmet cooling hours – so expect & make note of that swing in unmet hours so you can quantify & parse it out later for your own QC/documentation.
2. Based on the reference help entries, I’m concerned the night-cycle-ctrl inputs are intended specifically for the inverse case only (reacting only to provide heating when the system is off. I think the effect you’re looking for (turning on only when thermostat calls request it) can be achieved for PSZ by simply not defining a fan schedule (right-click, default that dropdown field). Either way, you can & should check/verify intended system operation via custom hourly reports for the associated system & control zone – include hourly zone temperatures, associated tstat setpoints, and something like fan operation/cfm to verify if the system is only operating when intended.
3. I’m not certain zonal exhaust inputs are necessary at all if you are modeling a 100% OA PSZ, but be cautious you aren’t ending up unintentionally “double-counting” fan energies between your PSZ fan power inputs and your zonal exhaust power inputs (or lack thereof). I think you can “zero out” the zonal kW/cfm or else make it a very tiny number if you do decide zonal exhaust inputs are needed.
Ah… The fact you intend to model hot water unit heaters probably throws a wrench into the advice/discussion so far…
“Furnace” generally implies gas combustion heating in doe2/eQUEST. That’s not what you want for hot water heating.
If it’s fair to assume the space is well-mixed during heating scenarios (i.e. not much stratification), then you can probably get by with accounting for the associated unit heater by specifying hot water baseboards with appropriate heating capacity in the zone. Have them controlled by a heating temperature schedule (sounds like you want this set to 60F all the time). You might want to specify the associated loop and boilers/meters first so that you can assign those in the same step. Downside to layering in baseboards as an approach is the unit heater fan energies won’t get picked up explicitly – the heat those contribute will instead be supplied by the HHW loop, and the energies associated with their fan operations for air circulation will not be picked up automatically. You could layer that in however (if it’s pertinent) by doing an hourly report to identify when baseboards are in operation (delivering heat), then assigning that to the space as an equipment load, capturing the heat contributions and electricity consumption.
If accounting for exhaust and unit heater fan energies operations separately/distinctly is a major priority… you’ll probably need to re-think the broader approach & system type selection. UHT is an attractive option for picking up unit heater operations explicitly and clearly on its own, but that system type affords no capacity to handle OA/exhaust. You’d either need to accomplish the exhaust/damper operations at the zonal level (spoon-feeding expected operations as a fractional or ON/OFF schedule since we’ve established thermostat schedules are not presently an option). You could alternatively pair UHT’s with an airside-system-based approach to the exhaust/damper operations (like the PSZ we’ve been discussing) if you split your zone/spaces geometrically to afford separations to assign different systems to, thermally connected with airwalls. Advantage to this approach is the flexibility to separate the conditioned volume if air mixing is not going to be stellar (stratification expected) during heating.
Hope this helps steer the ship!
~Nick
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Nick Caton, P.E., BEMP
Senior Energy Engineer
Energy and Sustainability Services
Schneider Electric
D 913.564.6361<tel:913.564.6361>
M 785.410.3317<tel:785.410.3317>
E nicholas.caton at schneider-electric.com<mailto:nicholas.caton at schneider-electric.com>
F 913.564.6380<tel:913.564.6380>
15200 Santa Fe Trail Drive
Suite 204
Lenexa, KS 66219
United States
[cid:image001.png at 01D189AB.58634A10]
From: Darryl Kasun [mailto:darryl.kasun at gmail.com<mailto:darryl.kasun at gmail.com>]
Sent: Monday, October 17, 2016 1:26 PM
To: Nicholas Caton <Nicholas.Caton at schneider-electric.com<mailto:Nicholas.Caton at schneider-electric.com>>
Cc: Brian Fountain <bfountain at greensim.com<mailto:bfountain at greensim.com>>; Julien MARREC <julien.marrec at gmail.com<mailto:julien.marrec at gmail.com>>; equest-users <equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>>
Subject: Re: [Equest-users] Modeling Reverse Acting TStat EF
Hi everyone - thank you so much for the replies. Just wanted to provide as a summary as to what I've modeled thus far - pls comment if you have any:
SYSTEM LEVEL:
- Modeled the reverse acting t-stat system as a PSZ with the following inputs at the system level:
- Control zone is the zone the supply fan serves
- Supply fan kW/CFM equals that of the EF
- Delta T across supply fan = 0
- Supply fan schedule is on/off type with default off for all hours
- Night Cycle Control: On Any
- min outside air ratio = 1.0
- CLG Cap left blank
- EIR = 0
ZONE LEVEL:
- HTG/CLG design temps are 60/80 degF;
- E/A control is "No Airflow Tracking"
- E/A flow matching the flow of the EF (11,000 CFM)
- E/A source: infiltration
- Max clg rate left blank
QUESTIONS REMAINING:
- Can I simply leave the CLG capacity to be auto-sized? Brian you had mentioned to put in a minimal value for this input but I do not understand why.
- This zone also has HW UHs serving it - how to I implement them? I see at the system level there's an option for the Zone Heat Source to be furnace which provides the opportunity to account for a UH's fan energy but looks like a furnace cannot be connected to a HW loop.
- Any advice of thermostat type?
Thanks again
Darryl Kasun
On Mon, Oct 17, 2016 at 11:04 AM, Nicholas Caton <Nicholas.Caton at schneider-electric.com<mailto:Nicholas.Caton at schneider-electric.com>> wrote:
Hey Brian,
You’re absolutely right – I should have double-checked before posting. In my mind’s eye, I recalled assigning a temperature schedule to zonal exhaust inputs, but it does appear I misremembered and that isn’t a direct option.
Tricking an airside system as you’re describing into the intended behavior must be how I’ve managed this in the past. A thermostat schedule is minimally needed at the system to define the intended “trigger temperatures,” and one could optionally also specify a fan schedule to go beyond intermittent and enforce off/on hours as might happen in the real world via tstat + relays.
~Nick
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Nick Caton, P.E., BEMP
Senior Energy Engineer
Energy and Sustainability Services
Schneider Electric
D 913.564.6361<tel:913.564.6361>
M 785.410.3317<tel:785.410.3317>
E nicholas.caton at schneider-electric.com<mailto:nicholas.caton at schneider-electric.com>
F 913.564.6380<tel:913.564.6380>
15200 Santa Fe Trail Drive
Suite 204
Lenexa, KS 66219
United States
[cid:image001.png at 01D189AB.58634A10]
-----Original Message-----
From: Brian Fountain [mailto:bfountain at greensim.com<mailto:bfountain at greensim.com>]
Sent: Monday, October 17, 2016 9:55 AM
To: Nicholas Caton <Nicholas.Caton at schneider-electric.com<mailto:Nicholas.Caton at schneider-electric.com>>; Julien MARREC <julien.marrec at gmail.com<mailto:julien.marrec at gmail.com>>; Darryl Kasun <darryl.kasun at gmail.com<mailto:darryl.kasun at gmail.com>>
Cc: equest-users <equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>>
Subject: Re: [Equest-users] Modeling Reverse Acting TStat EF
Does this mean the exhaust fan can cycle based on zone temperature? I had thought that the exhaust fan schedule was just on/off, on/off/flag and fraction. That means you have to pre-define the expected schedule rather than having the EF respond to the hourly space timestep temperature.
What we have done in the past is to model the EF as a PSZ with the fan power as the supply fan power and the "indoor fan mode" as intermittent. Cooling capacity set to a small non-zero value (as zero invokes auto-sizing).
Original Message
From: Nicholas Caton via Equest-users
Sent: Monday, October 17, 2016 10:39 AM
To: Julien MARREC; Darryl Kasun
Reply To: Nicholas Caton
Cc: equest-users
Subject: Re: [Equest-users] Modeling Reverse Acting TStat EF
From: Nicholas Caton
Sent: Monday, October 17, 2016 9:38 AM
To: 'Julien MARREC' <julien.marrec at gmail.com<mailto:julien.marrec at gmail.com>>; Darryl Kasun <darryl.kasun at gmail.com<mailto:darryl.kasun at gmail.com>>
Subject: RE: [Equest-users] Modeling Reverse Acting TStat EF
Yep - Julien has the right idea!
The other input of interest for your case is that at the same input screen, you can select the exhaust source as "infiltration," which means the associated makeup airstream = outside conditions.
~Nick
Nick Caton, P.E., BEMP
Senior Energy Engineer
Energy and Sustainability Services
Schneider Electric
D 913.564.6361<tel:913.564.6361>
M 785.410.3317<tel:785.410.3317>
E nicholas.caton at schneider-electric.com<mailto:nicholas.caton at schneider-electric.com>
F 913.564.6380<tel:913.564.6380>
15200 Santa Fe Trail Drive
Suite 204
Lenexa, KS 66219
United States
-----Original Message-----
From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Julien MARREC via Equest-users
Sent: Saturday, October 15, 2016 3:41 PM
To: Darryl Kasun <darryl.kasun at gmail.com<mailto:darryl.kasun at gmail.com>>
Cc: equest <equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>>
Subject: Re: [Equest-users] Modeling Reverse Acting TStat EF
Zonal exhaust fan has an option to control that on a temp schedule if I recall correctly.
Open the zone, tab "outside air" then at the right you can specify a zonal exhaust fan. (All this from memory so might differ slightly)
Cheers,
Julien
Envoyé de mon iPhone
> Le 15 oct. 2016 à 20:57, Darryl Kasun via Equest-users <equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>> a écrit :
>
> Hi eQUESTers,
>
> First off, you probably will not likely appreciate this and I'll preface this with saying that I'm a total bandwagon jumper but I am okay with that.
>
> GO JAYS!!!
>
> Now that that's out of the way I am trying to model a very simple system that I'm sure many of you have modeled before.
>
> I have a zone that has an exhaust fan in it. When the temp. reaches above 80 degF, an exhaust fan turns on and a damper opens to draw OA into the zone.
>
> I've been fooling around with a few systems trying to figure out a good way to model this but haven't come up with one yet.
>
> Let me know if have any recommendations.
>
> Thanks!
> Darryl
>
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