I will try to be concise but I'm also trying to paint the whole picture so please bear with me.
I'm building a hot water baseboard heating system from scratch. I'm using a tankless combination boiler that will provide service for heating and domestic hot water. Each floor will be able to be heated individually, so that's 1 zone for the basement, 1 zone for the main floor, and 1 zone for the upstairs bedrooms. Each zone will have two separate heating loops.
I will install a Vortech Air Separator at the Expansion Tank. I will also install automatic air valves at the beginning of each loop. My question right now is:
Even though I have an air separator at the expansion tank AND automatic air valves at the high points of heating runs, do I need to install bleeder valves at the baseboards to?
A parts list of the major components:
Navien CH-210-NG Boiler
Extrol #60 Expansion Tank
Taco 3/4" Cast Iron Vortech Air Separator
Taco 3 Zone Switching Relay (SR503-4)
Honeywell Thermostat (RTH8580WF)
Taco 007 Cast Iron Pump (007-F5)
Rifeng 2 Loop Manifold (RHM02-50PK)
Slant/Fin MultiPak 83A Baseboards
Taco 1/8" Hy-Vent (400-4)
3/4" Oxygen Barrier PEX-a
*keep in mind this list is not entirely complete, lists one of each major component, for example I'll have 3 pumps and 3 manifolds. Its just there to give you an idea of what I'm working with and does not include everything like thread adapters for pex tubing, etc. Major components only.
I'm considering adding Webstone 5062 Series Ball Valves w/ Bleeder. But not sure if I need them given the other levels of air purging.
I also want to add ball valves at the entry and exit point of each baseboard, the idea is simply to give myself the opportunity to replace a single baseboard should I need to in the future, but also not sure if that is overkill or might reduce head loss, etc.
I've also attached a heating diagram. Its a rough estimation of how the runs will look, don't pay too much attention to scale but it is fairly accurate. If you have any advice to offer on a maximum limit of baseboards per run, or maximum length of loop, or comparative size of loops on a zone (one loop shouldn't be more than x times larger than the other), that'd be much appreciated. But the diagram is there to help you visualize what I'm talking about.
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