[TRNSYS-users] Type700 question

[Nicholas LaHam]

Hi all,



I have a question about Type 700, the boiler component, if someone has
experience with it. I have a flow profile running into a tank, with a boiler
loop circulating through it to meet the energy demand. Boiler is set to 1
million kJ/hr which is just enough to meet the temperature demand of the
tank at its peak load.



Here is the problem:



I have my flow operating 4 days out of the week. At first I only had the
boiler turning off when the temperature was met (controller with 2, -2
deadbands). When I looked at the required boiler energy input integrated
over the course of the year, the number looked right, but I wanted to reduce
it. In order to do this, I used another controller on a time delay to lock
out the first controller the other 3 days of the week, so the boiler wasn’t
trying to heat the tank all weekend wasting useless energy.



What I noticed however was the required energy input barely changed. I know
the new controller works properly, because I can now see the tank
temperature dropping after the first 4 days and then not rising until a few
hours before the start of the week.



I think the energy savings should be more significant. I’m only saving
around 10 therms a year in  a 8500 gallon system. This is very small. The
boiler should be saving that at least every day it is turned off.



Any ideas why the difference is so small?
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