limited heat in HW & rads warm with only HW circuit on

[teejay246]

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

 

[HERTS P&D]

Drain down again and disconnect the pipe work to the coil. Use a wet vac to suck on one end of the coil, you should be able to suck out any debris.

Also x400 needs 4 weeks in a heating system, try x800 for 4 hrs.

Andy

 

[teejay246]

Thanks for the tip. I will give that a try. Just checking re "Wet vac". Am I safe in assuming you mean just a vacuum cleaner that will suck up water? Also am I to drain out the X800 mix with it - OR drain that out first? Apologies for the amateur query.

 

[HERTS P&D]

Yes drain first or you will get when you disconnect the pipe work to the hot water cylinder. I use a wet vac that I got from wickes.


Andy

 

[teejay246]

Thank you again. I'll give it a go when the weather warms up a bit.