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PostPosted: Thu May 11, 2017 2:44 pm 
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Hello, new to the forum and DIYing boilers.

I've got this old Baxi Combi 80 eco that has a couple of problems, but my issue is I wasn't able to drain it completely. The problems are: a leak on the diverter valve, and hot water temperature going up and down.

First very noob question: do I have to drain the whole system (all radiators) to fix something in the boiler? I want to fix the leak and it was my understanding that closing off all valves I would be able to drain just the boiler. However after draining it (with the heating flow and return valves closed, and cold water closed at the mains), and no more water coming out of the draining valve, when I started taking the diverter valve apart (unscrewing the front sensing pipe, see picture), a lot of water started pouring out, and even leaving it to drain for a minute it wouldn't stop. Could this mean some of the valves are broken, allowing water to come in? But then why is water coming that way, but no through the draining valve?

We use the water temperature control to turn it down when I'm having a shower, as the shower has no thermostat or anything on it (and it works just fine at low temp, it maintains my shower water temperature perfectly), and then turn it back to higher temps. However on higher temps at the tap in the downstairs kitchen the temperature fluctuates, and we cannot fill a hot bath upstairs as the water temperature drops. If we turn the tap down to slow down the rate of water, it warms up for longer, however then sometimes it triggers the protection, turning off the flame.

So the second question is: could the hot water temperature going too high and too low, even to the point where the protection kicks in turning off the flame, be related to the temp sensor? I measured the resistance while cold ~16°C it was showing 12.8k. It might also be dirty (hard water area) but was not willing to take it out because of the system not draining problem. I ordered a new one just in case. The boiler has LEDs to show temperature, and they seem to work, i.e. the LEDs light up slowly from 40°C to max 80°C before the system goes into protection. But the LEDs also stay at 80°C while the water temp drops in the kitchen, without the flame going off.

The boiler is quite old and had no maintenance in many years the valves underneath are quite corroded and might need changing. I didn't even know boilers needed maintenance until recently. It has worked quite well for years now, besides the water temperature problem.

Thanks for any help I get.

diverter sensing pipe.JPG
diverter sensing pipe.JPG [ 59.55 KiB | Viewed 697 times ]
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PostPosted: Thu May 11, 2017 3:40 pm 
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Once the boiler has been isolated from the cold mains, open a hot tap below the level of the boiler and as you slowly undo the said nut most of the water will drain from the open tap.

The boiler's drain valve only drains the heating side of the boiler, but again it will never drain fully so when a part is undone or removed there will still be some water come out.


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PostPosted: Mon Jun 05, 2017 11:05 pm 
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Hi did you get anywhere with these issues? I have the same boiler!

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