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UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions. |
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Heating and hot water failure
Guys
This could take some time to explain! I have a gas fired central heating and hot water system that is 9 years old. It comprises an Ideal 40k Btu boiler, Honeywell 4073 3 way motorised valve, hot water cylinder and thermostat, room stat, a Horstman Channel XL time control unit for HW and CH, and a Grundfos 15/60 pump. The problems started early this year with heating failure. My plumber changed the pump and three way valve electronic head (with the wrong item I discovered today). He got the heating running, but if the heating was on with the hot water (both are pumped via the three way motorised valve), the boiler would kettle up in about one minute and click off. So, we compromised and switched the hot water off at the wall controller and hey presto, the heating would run. We have used the immersion all summer for hot water. I tried the heating last weekend, and guess what, with the hot water off, the boiler kettles up in about one minute and there is no heat. The flow from the boiler is scalding, and the return stone cold. So, I figure it must be: 1. Pump failure 2. Three way valve failure 3. A blockage I replaced the three way valve last weekend, and no change. I took the (seven month old) pump off today and it works perfectly - I ran it with the bleed screw off and it spins without fault. I took it off its mounting to make sure it hadn't seized during the long summer layoff. I changed the Honeywell valve head for the correct one and still no heating or hot water. I lifted the carpet in the dining room and let the system drain through for one hour and the water coming out is CLEAR. I am absolutely stumped. Basically there is no return flow to the boiler for whatever reason. I can only imagine that there is a physical blockage in the return pipe. What do I do, strip pipes and re-solder new ones in? There has never been a dreadful sludge build up in my rads - I have taken them off several times for decoration etc and, OK, the water is a bit black, but there has never been excessive deposit. Does anybody have any suggestions as to: 1. What is wrong, and 2. How I fix it? I am on the verge of calling the plumber out but even he was baffled earlier in the year. Thanks Alex |