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Re: [EnergyPlus_Support] Radiant with DOAS sizing error



That was a good reply. This is the "other" kind of DOAS and is far less than typical (at least in Europe). 

To continue on "my" kind of DOAS...setup the setpoint managers for the AHU to supply air in a range of roughly 18 to 23 deg C. If the minimum outdoor air supplied at these extremes does not pick up the remaining zone loads when the zone equipment can't, then the zone equipment is not effective enough. Zone equipment is sized at air supply temperatures of 22  deg C (sizing:zone object).

Another hint for radiant systems:
Forget setback temperatures with delta T greater than 2 deg C, i.e. If your heating setpoint is 20 deg C, set your radiant system's schedule to 21 deg C with a throtteling range of 1 (so that the valve is fully open at Tzone 20 C, half open at 21 C and fully closed at 22 C. Then when you setup the setback thermostat to 18, also adjust the radiant system's schedule...and ramp up slowly from 18 to 20.

Mit freundlichen GrüÃ?en- Sent from my iPhone (excuse the brevity)

i. A.
Jean Marais
b.i.g. bechtold
Tel.   +49 30 6706662-23

On 25.06.2014, at 18:22, "Ery Djunaedy ery.mailinglist@xxxxxxxxx [EnergyPlus_Support]" <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:

 

HJ

You need to play with a number of parameters in Sizing:System and
Controller:OutdoorAir objects for your DOAS system.

If you size your DOAS on "ventilation" then there will be excess
heating and cooling that cannot be met. You can see this in the HTML
report under unmet hours. But if you changet the sizing to "sensible",
all of the excess heating and cooling will be met by the DOAS.

You need to set the equipment connection to set the priority on
heating and cooling of the zone between the radiant and the DOAS.

If you have big DOAS coils as the result of your autosize calculation,
you need to say "No" to 100% OA when cooling and cooling. With this
setting, you will have DOAS most of the time but when there is extra
heating and cooling beyond the ventilation load, then the OA fraction
will be reduced to meet the load.

Ery

On Tue, 24 Jun 2014, HJ wanghaojie630@xxxxxxxxx [EnergyPlus_Support] wrote:

> Hi all,
>
> I have some projects that has radiant system with DOAS. I find
> EnergyPlus could not size this type of system properly it never try to
> meet the thermostat temeprature. When I look at the summer or winter
> design condition, the temperature could go as high as 30 or as low as 7.
> I used openstudio to export to EnergyPlus. For radiant system, it does
> not use thermostat but use its only temperature control, I wonder if
> that could be the problem for sizing? Does anyone have any successful
> experience with this type of system sizing and could share your idf file?
>
> Many thanks,
>
> HJ



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