[EnergyPlus_Support] Re: Water/Water HX ~ WaterHeater:Mixed

["Jean marais" <jeannieboef@xxxxxxxxx>]

1) energy plus sizes radiant and airloop systems indepenantly, but with the same heating cooling sizing parameters. That means if my radiant system is sized to meet the whole load, by default the airloop system is also sized to meet the whole load.


2) The heating setpoint (for the airloop) is currently used to count unmet load hours. I've not tried setting it to zero yet. I do fear that the radiant system for heating alone will produce too many unmet load hours (although I've not written an EMS to record them yet...the easier option would be to just turn the heating coil availibillity off during occupied periods). I'm sick at home today and will see how many unmet hours I get tomorrow. I have yet to include building infiltration, which would make it even worse though. Like I said before, the ideal sollution would be to cycle heating coil operation. To meet loads not met by the radiant system. I could have a look at hot water coil controller options.  


--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, "Jim Dirkes" <jim@...> wrote:
>
> Dear Jean,
> 
>  
> 
> Is there any reason your air system has sufficient heating capacity to heat
> the entire building? Or perhaps I should ask why you have allowed the air
> loop setpoint to be high enough to heat the entire building?
> 
>  
> 
> The Building Performance Team
> James V. Dirkes II, P.E., BEMP , LEED AP
> 1631 Acacia Drive NW
> Grand Rapids, MI 49504
> 616 450 8653
> 
>  
> 
> From: EnergyPlus_Support@xxxxxxxxxxxxxxx
> [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of Jean marais
> Sent: Monday, November 07, 2011 9:03 AM
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> Subject: [EnergyPlus_Support] Re: Water/Water HX ~ WaterHeater:Mixed
> 
>  
> 
>   
> 
> Dear James,
> 
> 2) My priorities are already set like this. When the fan mode is cycling
> (during unoccupied times) to meet the setback temp of 18 deg (see exception
> for radiant systems) the radiant system performs beautifully to cover 99% of
> the loads with the cycling system kicking in to cover those occational times
> where the reaction time of the radiant system is not fast enough. However,
> when fan mode switches to continuous, the priority becomes a moot point as
> the fan system can and does cover 100% of the loads. What I really need is
> the heating coil to cycle while the fan remains contantly on. I have
> considered turning it off (during occupied times) just to see how many unmet
> hours it comes to. Dr Li's idea of dropping the heating setpoint temp during
> these hours is tempting, because I'll get zero met load hours and as the
> radiant system has its own setpoint temperature, I could claim that my
> heating setpoint temperature and schedule remains the same in both the
> baseline and proposed models (but then the unmet load hours for radiant
> system is not calculated by e+ and would require an EMS to tally). 
> 
> 1) I know this has been done successfully on LEED projects, but have
> declined it out of principle. When reading the user manual for 90.1, it is
> clear that the reason for having to model a cooling (or heating) system
> where non exists, is to cover the case that under-conditioned facilities
> will inherrantly retrofit these systems over the life of the building to
> insure user comfort, i.e. they will retrofit air conditioning systems
> because the users will complain, to increase rent, enforcement by law or
> other reasons. I don't think that retrofitted systems would not be used by
> the building users.
>




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