I have read the various questions asked about setting up solar thermal DHW systems but I just want to try and clarify something.
We have a building with gas hot water heating. The client wants to omit this and install solar hot water with electric immersion back-up for various reasons.
I have therefore changed my default DHW to fuel from natural gas to grid electricity then used the SES tab for Default DHW and set up the system. I have used the same names and included water storage (as for the gas system) with 8.8m² of panel area. I have included a pumped loop with PV, as we have a PV system on the building.
When I get results I can see that the solar thermal is included but we go from a pass to a fail and the carbon emissions and primary energy figures (needed for compliance in Wales) are significantly increased over gas hot water although the actual hot water energy allocation has dropped significantly.
I changed the DHW fuel to natural gas and kept all the solar thermal stuff and we then get a flying pass.
This seems to suggest that using an all electric solar thermal system, even with PV, is very poor compared to gas hot water.
Just wanted to check that I am setting this up correctly and my results are correct before I advise my client.
Hi Keith,
It sounds like you are running a PartL calculation is that correct? If so, electric systems such as this are often penalised quite heavily in comparison to gas, so this would not be altogether surprising. It sounds to me like you have set the system up correctly, however as Hevacomp only acts as the interface to the SBEM calculation (further guidance on this here) the final say would have to come from your accreditation scheme provider. They will be in a much better position to advise.
Shane Regan | Principle Building Performance Support EngineerHevacomp to OpenBuildings - A complete guide for every user | Bentley Communities