IES-VE User Forum

I have modeled a house with 3 people occupancy and I want to see the predicted dhw consumption with and without the solar thermal system. Basically, I ran the model with and without the 'Solar heating system' ticked/unticked in the 'systems' and the DHW system box ticked to 'use same as HVAC'. However, when looking in vista when analyzing the case with solar thermal (providing hot water only) - the energy demand would be sum of demand required by boiler + demand required by solar thermal system. Demand required by boiler (which i presume I determine through the tab in vista 'Ap sys boilers DHW energy') should be at a smaller for the case without solar thermal than with (because the solar thermal should in theory reduce the energy required by the boiler to heat hot water). However, my model doesn't show this. Would you know why?

I took 'Ap Sys aux + DHW/solar pumps energy' as the extra energy required to operate the solar thermal system due to the pump etc. Is that what Ap Sys aux + SHW/solar pump energy means?

Many Thanks
Theresa

The pump power box in AP systems will affect your pumping energy, the pumping and aux energy i think also includes fan energy that may be set up as a local supply / extract.

Clearly solar hot water should reduce boiler energy. Unless you have set up the "DHW consumption" under room conditions you may not get any results for HW energy anyway. I would check this first, change the amount of HW you are using and see what affects it has on the energy's.