Re: [EnergyPlus_Support] Flow control between floor heater and solar storage tank

Dear,

As You recommended I made a schematic of the solar collector and floor heating loops (Attachement). So I am wondering is it possible to do following:

- if the temperature of the return water from the floor heater (Node OFH (from Figure)) is higher than the temperature of the water exiting the storage tank (Node OST (from Figure)) all water flow goes directly to the gas boiler (instantaneous water heater) (does not go through the storage tank).

Regarding this problem I asked You is it possible to simulate this and if it is what is the best solution:

- to use EMS actuator called "Plant Component*" that is available with the control type "On/Off Supervisory". So, if temp. for Node OFH > temp. for Node OST than the value of this actuator will be 0 which directs component (Storage tank (WaterHeater:Mixed object)) to shut down.

- to use EMS in the following manner: if temp. for Node OFH > temp. for Node OST than temp. for Node OST = temp. for Node OFH.

- some other solution (???)

I am not sure is it possible (maybe i am wrong) to use System availibility schedules and temperature schedules because the return temperature from the floor heater differs regarding the heat load.

THANK YOU IN ADVANCE

Novak

On Tuesday, June 17, 2014 2:39 PM, "jeannieboef@xxxxxxxxx" <jeannieboef@xxxxxxxxx> wrote:

It may be helpfull to include a schematic of the loops you want to have. I can't judge if your loops are holding to the rules. You also get more responses from other forum members.

As for EMS...the easiest way to implement EMS is to manipulate (overwrite) the values that come from schedules (of any kind). System availibility schedules and temperature schedules are typical candidates. For example, I set a sensor to monitor the exiting water node temperature (on a node of your choice) and when it is more than 20, I set the system availibility schedule of an equipment that uses it to 0, thereby disabling the equipment.

Mit freundlichen GrÃ¼Ã?en- Sent from my iPhone (excuse the brevity)

i. A.

Jean Marais

b.i.g. bechtold

Tel. +49 30 6706662-23

On 17.06.2014, at 13:38, Novak Nikolic <lepinole@xxxxxxxxx> wrote:

Dear,

First of all I would like to thank You for your response. My floor heater refers to the lowtemperatureradiant:variableflow (constant supply temperature) object. I agreed with You that the return temperature will vary because the system has a capacity to meet design loads at design conditions and the conditions of both radiant surface temperatures and room air temperatures effect the convection coefficients and hence the heat transfer characteristics. Anyway, in my case I want to order EnergyPlus that if the return water temperature from floor heater is lower than the water temperature in the solar storage tank the water goes directly to the gas boiler. I am planning to use EMS object but I do not know is it possible.

Is it possible to use EMS actuator "Plant Component*" in order to turn off storage tank when the previously mentioned situation appears? Or is it better to order EnergyPlus that if above situation appears the outlet water temperature from the storage tank be same as return water temperature from the heater?

Is it possible to use this EMS object with tempering valve object in the same time?

Thank You in advance

Novak

On Saturday, June 14, 2014 10:05 AM, "'jeannieboef@xxxxxxxxx' jeannieboef@xxxxxxxxx [EnergyPlus_Support]" <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:

I think your floor heater refers to the lowtemperatureradiant object. There are two versions: constantflow (variable supply temperature) and variableflow (constant supply temperature).

The first model inherrently mixes the return water temperature to the supply water to attain required supply temperature to satisfy the load at constant flowrate for the radiant tubing. This is "inside" the model and you can't really see the model internal node temperatures. It basically has the tempering built in.

The second model is fed with a set temperature (you can put a setpoint manager here to do this). The model will demand more or less flow depending on the load and the supply temperature should be kept as per the setpoint manager.

In both models the return temperature will vary because the system has a capacity to meet design loads at design conditions and the conditions of both radiant surface temperatures and room air temperatures effect the convection coefficients and hence the heat transfer characteristics.

Setting up a constant heat transfer system (constant water dT) is probably possible, but would require an EMS to dynamically adjust a temperature setpoint or mass flowrate as well as a system with enough capacity.

Mit freundlichen GrÃ¼Ã?en- Sent from my iPhone (excuse the brevity)

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

On 13.06.2014, at 13:25, "lepinole@xxxxxxxxx [EnergyPlus_Support]" <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:

Dear colleagues,

I am trying to simulate a heating system that includes solar storage tank, condensing boiler and floor heater. I am wondering if it is possible to control the water flow from the floor heater and solar storage tank depending on the difference between the outlet water temperature of the floor heater and the outlet water temperature of the solar storage tank. Precisely, is it possible to say EnergyPlus that when the outlet water temperature of the floor heater is warmer than the outlet water temperature of the solar storage tank the all flow (from floor heater) goes directly to the boiler not in the storage tank. Contrary, when the outlet water temperature of the floor heater is colder than the outlet water temperature of the solar storage tank the all flow (from water heater) goes to the the storage tank. I know there is a tempering valve object but it can be used only in situation when the outlet water temperature from the tank is too high.

In a hope that someone will answer and help me I thank You in advance.

Novak Nikolic, research assistent