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How to model Indirect Water Heaters in OpenStudio?

Hello everyone,

I'm trying to model an indirect water heater using OpenStudio 1.5.0 and Energyplus 8.1. I've got the water heater (WaterHeaterMixed object) attached to the demand side of my heating water loop, and I've input the peak water use load under the Peak Use Flow Rate entry for the water heater, as well as specifying a Use Flow Rate Fraction schedule. I've also specified a tank size and a capacity for the heater.

When I examine the output, however, I'm getting ridiculously high natural gas used for water which is constant for every month (varying slightly based on the length of the month). It's saying 100+ MMBtu per month for a 1100 m2 building.

My question is two parts:

1) If the water heater is on the demand side of a boiler loop, does specifying a capacity and a Natural Gas fuel type double count the natural gas used to heat water?

2) What inputs should I look at to control the indirect water heater properly?

How to model Indirect Water Heaters in OpenStudio?

Hello everyone,

I'm trying to model an indirect water heater using OpenStudio 1.5.0 and Energyplus 8.1. I've got the water heater (WaterHeaterMixed object) attached to the demand side of my heating water loop, and I've input the peak water use load under the Peak Use Flow Rate entry for the water heater, as well as specifying a Use Flow Rate Fraction schedule. I've also specified a tank size and a capacity for the heater.

When I examine the output, however, I'm getting ridiculously high natural gas used for water which is constant for every month (varying slightly based on the length of the month). It's saying 100+ MMBtu per month for a 1100 m2 building.

My question is two parts:

1) If the water heater is on the demand side of a boiler loop, does specifying a capacity and a Natural Gas fuel type double count the natural gas used to heat water?

2) What inputs should I look at to control the indirect water heater properly?

How to model Indirect Water Heaters in OpenStudio?

Hello everyone,

I'm trying to model an indirect water heater using OpenStudio 1.5.0 and Energyplus 8.1. I've got the water heater (WaterHeaterMixed object) attached to the demand side of my heating water loop, and I've input the peak water use load under the Peak Use Flow Rate entry for the water heater, as well as specifying a Use Flow Rate Fraction schedule. I've also specified a tank size and a capacity for the heater.

When I examine the output, however, I'm getting ridiculously high natural gas used for water which is constant for every month (varying slightly based on the length of the month). It's saying 100+ MMBtu per month for a 1100 m2 building.

My question is two parts:

1) If the water heater is on the demand side of a boiler loop, does specifying a capacity and a Natural Gas fuel type double count the natural gas used to heat water?

2) What inputs should I look at to control the indirect water heater properly?