05-02-2013, 04:49 PM
"I see no problem Lawrence. There would be the normal feed and expansion tank and it would be just like shutting off one of the valves, in a two valve setup. Used to keep the rad one shut all the time in the summer"
That sounds about right Gary, our present system has worked fine so far but as the building has progressed I have replaced the old radiators as we went along which for me means draining down the system which is no problem, the problem arises when the system is re filled as in trapped air. Because the building isn't very high the header tank is barely above the flow and return pipes, originally there was a Baxi open fire back boiler fitted for the HW and CH it worked ok but open fires arn't very efficient, the previous owner had used 15 mm for the main flow and return which ran through the ceiling they then dropped down to each radiator with that bendy 8mm small bore copper pipe.
We decided to replace the open Baxi with a woodburner and also replace the radiators as they were well past it.
In general the 15 mm flow and return pipes that ran through the ceiling were pretty inaccessible for replacement with 22 mm but the T junctions feeding the 8mm pipe to the radiators were, so we left it at 15mm for the main flow and return and changed the T junctions for 10 mm ones and dropped 10 mm copper bendy pipes down to each of the new radiators. All this works fine, the Grundfos CH pump is set to the slowest of the three speeds, in fact the Grundfos is the original as fitted by the previos owners. From the boiler to the CH pump and the CH pump to the start of the 15 mm flow and return (just before it dissapears into the ceiling is 22 mm pipe.
Getting the trapped air out after a drain down and refill normally takes around a week, I always use plenty of inhibitor.
Lawrence.
That sounds about right Gary, our present system has worked fine so far but as the building has progressed I have replaced the old radiators as we went along which for me means draining down the system which is no problem, the problem arises when the system is re filled as in trapped air. Because the building isn't very high the header tank is barely above the flow and return pipes, originally there was a Baxi open fire back boiler fitted for the HW and CH it worked ok but open fires arn't very efficient, the previous owner had used 15 mm for the main flow and return which ran through the ceiling they then dropped down to each radiator with that bendy 8mm small bore copper pipe.
We decided to replace the open Baxi with a woodburner and also replace the radiators as they were well past it.
In general the 15 mm flow and return pipes that ran through the ceiling were pretty inaccessible for replacement with 22 mm but the T junctions feeding the 8mm pipe to the radiators were, so we left it at 15mm for the main flow and return and changed the T junctions for 10 mm ones and dropped 10 mm copper bendy pipes down to each of the new radiators. All this works fine, the Grundfos CH pump is set to the slowest of the three speeds, in fact the Grundfos is the original as fitted by the previos owners. From the boiler to the CH pump and the CH pump to the start of the 15 mm flow and return (just before it dissapears into the ceiling is 22 mm pipe.
Getting the trapped air out after a drain down and refill normally takes around a week, I always use plenty of inhibitor.
Lawrence.
