Electrical loads

Brad White_75

about TRV's... absolutely. Focus on power-in and miss the bigger picture. What I love about The Wall.

Jacob_3

Electrical load calculations

Thought I'd throw this one out there, see if anyone has a solution for me. I'm trying to determine average daily electrical draw for an off grid system with all PV power supply. System will either be a wood boiler with injection or a GB142 propane boiler, depending on customers choice. System is 3 zones with 24V zone valves and a single circulator. Thanks guys.

Brad White_75

I would think

200 Watts would cover your heating system with room to spare, not knowing any specifics. A Grundfos or similar small circulator (15-58 Brute) draws 87 W at high speed, 60 W at low speed. If you have injection there may be another albeit smaller one there. Burner data you can get from the manufacturer.

I have a Monitor MZ which draws by nameplate 108 Watts, 80 or so of that being the built-in circulator, so the burner, controls and fan are the only difference. I have an external secondary circulator so my total draw is about 175 Watts. That is how I arrived at the 200 number in rough terms.

All of this is per hour and depending on control setup (constant or intermittent circulation, variable speed injection, etc.) your hourly demand will of course vary. Multiply by hours of operation of course.

Everything you need to know is on the nameplates. Sites that deal in PV systems such as Real Goods have web worksheets for overall system estimates. Have a ball!

jp_2

trv's

this sounds perfect for a trv type system.
if i were off the grid, as i am, I wouldn't like the idea of zone valves, PV systems seem real expensive, so killing every unnecessary watt is useful.

also sounds good for a high mass/passive solar system.