[BLDG-SIM] eQUEST-System no heating

Thu Aug 23 09:26:39 PDT 2007

The default for VAV is to send air to the zones at 55F (13C). Depending on how much outdoor air is part of the supply air, you may/may not need heating at the system level. The increase from 55F to 90F (or whatever the supply temp is during heating) happens at the reheat coils (which are at the zone level). The preheat will depend on the amount of outside air. Hope this helps.

- Rohini

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From: BLDG-SIM at gard.com [mailto:BLDG-SIM at gard.com] On Behalf Of Zhen Tian
Sent: Thursday, August 23, 2007 11:46 AM
To: BLDG-SIM at gard.com
Subject: [BLDG-SIM] eQUEST-System no heating

Thanks, Michael.

I did try the steps according to your suggestions. But I found the following issues.

In my model (detail model), I did not install  the preheat coil. After I install the preheat coil, I found that no matter how I increase the capacity, the heating energy use for preheat coil is very small. I also tried to put design day data into the detail mdel, it igave me the same result too.

Based on my understanding, the zone level reheat coils are for space heating load through building envelpe and infiltration; the main system heat coil is to handle ventilation heating load. The preheat coil is just to preheat incoming air to prevent frost.

So I dont understan why the heat and preheat coil heeat energy use is so small in the very cold climate (zone 7). In my model, the heat recovery was not installed and the space type is regular office.

Any suggestion is greatly appreciated.

Thanks.

Regards,

David

Michael Andelman <mike at andelmanlelek.com> wrote:

	From: "Michael Andelman" <mike at andelmanlelek.com>
	To: <tianzhen9 at yahoo.com>
	Subject: RE: [BLDG-SIM] eQUEST-System no heating
	Date: Thu, 23 Aug 2007 10:21:34 -0400

	If you do not assign a capacity for the preheat coil, it is self sized based on heating design day information (not the outside temperature from the weather file).
	The wizard creates a HDD for California ¡V you need to change the HDD outdoor temperature or enter a coil capacity.

	Mike

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	From: BLDG-SIM at gard.com [mailto:BLDG-SIM at gard.com] On Behalf Of Zhen Tian
	Sent: Wednesday, August 22, 2007 3:09 PM
	To: BLDG-SIM at gard.com
	Subject: [BLDG-SIM] eQUEST-System no heating

	Hi Aulbach,

	Thanks for your reply. Yes, I inpu everything into the detail mode. Based on the system design in climate. The air system has three typies of heating: 1) preheating for preheating the incoming air to around 5 degree C; 2) main system heating coil to heat the incoming air (this heat coil is arranged after cooling coil); 3) reheat coil, this is the reheat coil in zone level to meet the zone temperature requirement.

	The one I found is the 2) main system heating coil never works. In the model, the preheating coil was ignored. Seems that all heating load goes to the zone level reheat coil.

	Any idea about this?

	Thanks.

	Regards,

	David  

	"Aulbach, John" <jaulbach at nexant.com> wrote:

		I am going to take a stab at this one. In eQuest, a VAV system is a Terminal System. Therefore, in the Wizard, the zone level is where all heating and/or reheating is done (and developed). You have to force a primary heating source to occur, but this doesn't appear in the Wizard mode, apparently..

		Have you input a Reheat-Delta-T? The temperature of 55 DegF + 40 DegF = 95 DegF heating supply temp.

		I also do NOT find the ability to create a pre heat coil in the Wizard. I have done it, but am quite sure this was input in the Detailed Interface Mode. There are MANY eQuest features that become available (like more SYSTEM-TYPES) in the Detailed Mode.

		Once you have "cookie cuttered" your building in the Wizards, switch to the Detailed Mode. There you will find your preheat coil.

________________________________

		From: BLDG-SIM at gard.com [mailto:BLDG-SIM at gard.com] On Behalf Of Zhen Tian
		Sent: Wednesday, August 22, 2007 9:49 AM
		To: BLDG-SIM at gard.com
		Subject: [BLDG-SIM] eQUEST-System no heating
		Dear All,

		I experienced an issue when I use eQUEST. I model a building in cold climate with VAV system. In the wizard mode, I found the system heat source is "not installed". But when I change to electricity, I found the heating enery use for system heating is zero. I also tried other options, always found that the system heat source is useless. I found that all the heating goes the zone level. Based on my understanding, this should not be the real case.

		I set the air supply temperature as constant as 55F (around 13 degree C), zone entering max air tem as 95F. Enen I set the zone entering max air tem as 86 (30 C). The system heating coil still has no load.

		Has anyone experience the same problem before and know to to solve this problem?

		Thanks a lot.

		Regards,

		David

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