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RE: [EnergyPlus_Support] Re: on/off boiler
Hi, T.T
You need to describe a system in total, and not in parts.
I have switched to text mode, as my RTF(HTML) did not show, in your reply.
You may have more than two thermostats in the system, one for each radiator in a room. When a radiator is turned off, the water flows through the by-pass pipe.
The pump may not be turned off by a thermostat. It can be a flow/pressure sensor. If it is a thermostat, then there is no individual radiator room temperature control.
The boiler thermostat is usually a biased on/off switch. That is providing you with the on/off temperature values. Therefore, it need not be simulated. So is your room thermostat, which has a set-back builded in. The simple mercury switch cannot flip and flop back immediately without a temerature change.
A digital thermostat requires a program to set the on/off temperature. It may not be under user control.
===================================
PLR is not the maximum power of the components.
A system which is on all the time has a PLR of 1.
When the PLR is less than 1, it is in the on/off mode.
When the PLR is zero, the system is off all the time.
Therefore, your three PLR ratio is incorrect.
You wanted the boiler to stay on all the time with maximum heating and maximum pump speed. In other words, no control. Hope you do have a safety valve installed to turn off the heating power.
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A gas fire, a fan or pump with a constant speed motor has a PLR when running in on/off mode.
A variable speed motor requires a controller, a sensor, and an algorithm. The variable speed fan or pump in EPLUS includes the constant speed operation mode option.
Dr. Li
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: t.t111ir@xxxxxxxxx
Date: Fri, 20 Jan 2012 09:14:08 +0000
Subject: [EnergyPlus_Support] Re: on/off boiler
Dear Dr.Li,
yea you are right i agree with you completly about " comfort requirement and energy saving does not go together that "
, but you know in my country IRAN , in almost building there is the system with two thermostat : one thermostat is for boiler and another for its pump , and usually pump starts earlier than boiler .
by the way for modeling this on/off boiler that works at its maximum capacity i used :
maximum part load ratio = 1
minum part load ratio =1
optimum part load ratio =1
is that right?
thanks
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, YuanLu Li <yli006@...> wrote:
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