Answer to question from JB Tech Talk No. 5 – if the secondary flow increases, T2 will drop and either the primary flow or temperature will have to increase proportionately to meet setpoint at T2.
From Wikipedia – ‘A checklist is a type of job aid used to reduce failure by compensating for potential limits of human memory and attention.’ To try and save some time when called about a problem, I developed a check list to quiz the customer before hopping in the car. The original copy is long lost, but here’s a re-creation that I believe is close to it:
• Get a description of the problem. (Not just, ‘it doesn’t work.’)
• Power on? Followed up with ‘Did you check?’ – applicable to the whole list
• Gas on?
• Rotation correct?
• All valves in correct position?
• Strainers and filters clean? Really clean? Did you take it apart?
• Flues clear?
• Flow direction correct on check valves, flow switches, etc.?
• Fuses okay?
• Is there a control demand?
• Air vented from hydronic systems?
• Any fire dampers closed?
• Other dampers (outside air, return air, exhaust) in correct position?
• Back-draft dampers swinging freely?
• Cold static fill pressure properly set for the height of the system?
• Coils/heat exchangers/boilers piped correctly?
I should also mention that a lot of equipment has similar check lists in the installation instructions. Bazinga!
The responses I got to some of the questions were a bit spicy; I’ll leave that to your imagination. But there were some guys who had to pull in their horns when they discovered the problem. I’m no different; I’ve struggled with issues to ultimately find it was something so obvious that it’s embarrassing. My own ‘limits of human memory and attention’ are not just potential; they’re real and not getting any better with time.
Going through this process saved me some long drives and quickly solved the problem for the customer. I hope it might be helpful to you as well. I also believe that after being grilled once or twice it made people start checking the basics before they called. Win-win.