Re: [EnergyPlus_Support] Boiler Loop Problems

Jim,

With a setpoint manager on the supply outlet, you should be getting a constant loop outlet temp. It's the supply inlet temp that will vary.

Regarding variable pumping - I'm not that familiar with the primary/secondary loop in EnergyPlus. Another way to approach it is to actually use two plantloops and connect them through a water to water heat pump with COPs in the thousands. This might give you a little more flexibility.

--

Karen

On Sat, Apr 28, 2012 at 7:20 AM, Jim Dirkes <jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

Karen,
The setpoint manager is on the outlet of the supply loop, as you suggest.

..and with a constant speed pump serving both boilers, I agree that the loop temp will vary.
Perhaps my real problem is this:

·         In the real system, there is one (primary) pump per boiler and a VSD pump on the secondary side

·         How do I model that or make an equivalent?

·         And thus get constant loop outlet temps?

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 Karen Walkerman
Sent: Saturday, April 28, 2012 6:28 AM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: Re: [EnergyPlus_Support] Boiler Loop Problems

Where is your setpoint manager located? You should be able to maintain a constant temperature on the supply outlet branch. At constant flow, this means that your loop temperature differential will vary.

--
Karen

On Friday, April 27, 2012, jvd2pe <jim@xxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
>
> Dear Forum,
> I think I figured this out sometime ago, but have forgotten what I did?..
> ? I have a PlantLoop with 2 boilers and a Bypass
> ? I am using "CommonPipeSimulation" in my PlantLoop definition in order to incorporate a secondary / demand side pump.
> ? E+ does not like supply side variable speed pumps when CommonPipe is used, so I am using a constant speed pump (P1) on the inlet branch.
> ? B1 and B2 do not run continuously. B1 runs most of the time and B2 operates only when B1 cannot carry the load.
> ? Since P1 runs continuously at constant speed, the water temperature leaving the Supply Outlet is diluted ? it's a blend of the B1 outlet temperature and the remainder of the flow, which goes through the bypass.
> ? I don't want diluted outlet temperature! (It's degrading coil performance on the demand side)
>
> Suggestions, please!
> p.s., If I get that part solved, the next step is to figure out how to make P1's power vary with flow.
> p.p.s., I tried to send this twice previously, but it has not shown up, so I'm trying again....
>
>