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Posted by HeatPro on May 12, 2006 at 13:13:55:
In Reply to: Re: radiators for hot water heating systems posted by joe on May 12, 2006 at 12:08:49:
You are asking if you should have a one-pipe or multi-loop series system. The one-pipe system has advantages for a simple house with few odd extensions. Every room can have its own zone with zone valves then. A one-inch main can handle the 60,000 btuh with one circuit.
If you are looking to get the most out of the condensing boiler, cabinet-heater setup you want: Install the system as two-pipe (European style) with a branch and zone valve for each cabinet. If you have a basement the zone valves can go down there. If not, there is room in the cabinet.
To get the most out of the system, pipe the 3/4 or 1-inch supply main to the cabinet elements with 1/2-inch to the top of the multiple elements so the hotter water goes to the top elements and cools on the way to the bottom element. Have the return come off the bottom to the separate 3/4 or 1-inch return main. Use balancing valves in each supply so the flow can be tailored so there is a 40F degree drop from supply to return at the cabinets. This assures cooler return water to the condensing boiler to get the max efficiency. There is not enough surface on 3/4 tubing to worry about significant losses; but it is a good practice to insulate the tubing to assure the maximum savings. This is more typical of European installations to save on fuel costs which are still twice as much as US costs even with the recent fuel cost increases.
The one-pipe and multiple series loops are more for non-condensing installations of older cheap-fuel days.