Dear All,
My previous message did not get any answers, so with the hope that maybe
I catch the attention of some expert modelers with knowledge on this
subject, I am repeating my question. Any help would be appreciated.
A multifamily high rise residential will be heated by floor convectors
with both natural and forced convection. In most cases, natural
convection will be sufficient (this is the experience of the mechanical
engineer) and warmed air will rise from these convectors into the
spaces. In colder weather, the convectors will operate their fans for
more airflow.
I have not been able to find much about modelling such a device. My
intuition tells me that system Fan Coil would be the best candidate, but
with fan power and airflow tied to a schedule that is dependent on
outside air temperatures. Is this possible in eQuest?
The difficult part is that in warmer weather fan power will be zero and
there will be some airflow, while in colder weather fan power will
appear and there will be higher airflows.
Thanks for any help,
Omer Moltay
?mer,
There are different ways you could include the fan energy in the model, depending on the following:
How are these convectors controlled? What controls the heat output, and what triggers the fans to come on?
Are the convectors electric heating or hot water?
Is there a separate air handler for ventilation?
How about modeling the convector heating as hot water (regardless of whether or not they are). Assign two boilers (electric if the convectors are electric), one with a separate boiler pump to represent the convector fan, and one without. Create an equipment control that uses the boiler without pump as the first stage of heating, and the boiler with pump as the second stage. This method models the fans as coming on at a certain stage of heating load, instead of them coming on per a time schedule or OA schedule.
Some other ideas:
If the convectors are hot water, you could model them as hot water baseboards, and add a miscellaneous load with a schedule that mimics the hours that the convector fan would run.
If the convectors are electric, you could model them as hot water baseboards with an electric boiler, and the HW loop pump can represent the fan. Add a miscellaneous load with a schedule that mimics the hours that the convectors are natural convection only.
You could also try to model the convectors as variable volume, so that the fan curve results in lower fan power at lower loads.
Regards,
Bill
One method that I have used is to use a fan coil or unit heater system
(depending on if cooling or outdoor air is required) with baseboard heat.
A fan powered convector will provide much more heat than one without the
fan. Typically I set the baseboard capacity to10-15% of the heat capacity
of the fan powered convector. This will vary for hot water heating systems
based on the HW and space temperatures. The balance of the heating
capacity is then used for the fan coil or unit heater.