I have read over 40 pages of posts so far without an answer so new post. I have a 30yr old open vented fully pumped system in a 2 storey bungalow. Ideal Mexico boiler with separate CH and HW. Pump is on the return side, by the boiler on the ground floor. HW flow also goes to F&E tank via a tee. HW return has a rad valve on it as it comes off the coil by the tank. System - 18 radiators split into 2 zones controlled by Honewell 2pt zone valves. After new pump installed, we started having over-pumping issues. Twice used X400 in system over weeks followed by full drain and re-fill. Over-pumping subsided recently only to be replaced by HW being less hot than it should, also noticed pipes to rads were warm and all rads would heat somewhat if only on HW. My CH guy suggested blockage in piping to the HW coil or in the coil itself - resistance he called it and noted that water in the F&E tank was warm confirming this. I did a partial drain down, disconnected HW tank coil and set up a flush having left X400 in the coil for a couple of hours. Heat in water improved but warm seapage into CH pipes when on HW only.
CH guy came again and noted it is NOT reverse flow. He advised disconnecting flow from HW coil and blowing down it. Same with return. If OK problem is resistance/blockage in the coil. Schematic of my system is attached. If this is so, how best can I clean out the coil, and any other advice/info you can offer. I replaced the valve with a new one on the return side of the coil. It's fully open?? I used mains pressure with last flush of coil but it was cold of course. Hope the pic is clear enough.
Thanks
CH guy came again and noted it is NOT reverse flow. He advised disconnecting flow from HW coil and blowing down it. Same with return. If OK problem is resistance/blockage in the coil. Schematic of my system is attached. If this is so, how best can I clean out the coil, and any other advice/info you can offer. I replaced the valve with a new one on the return side of the coil. It's fully open?? I used mains pressure with last flush of coil but it was cold of course. Hope the pic is clear enough.
Thanks