ideal Mexico - CH working but not HW

GoodOne said:
I got strong jet of water out when i bled it.
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That would suggest there is adequate water in the system, and the circuit is full of water. My money is on a blockage in the pipework, only way to see is to drain down again, and break into the primary pipework. Before doing so, run your magnet very carefully along as much of the pipework as you can get to, particularly around the cylinder. Any sign of the magnet being attracted would indicate a problem within. That's where to start looking first.
 
Hugh Jaleak said:
That would suggest there is adequate water in the system, and the circuit is full of water. My money is on a blockage in the pipework, only way to see is to drain down again, and break into the primary pipework. Before doing so, run your magnet very carefully along as much of the pipework as you can get to, particularly around the cylinder. Any sign of the magnet being attracted would indicate a problem within. That's where to start looking first.
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My thoughts would be the coil could have a high point where air has been trapped, not such a problem with a fully pumped system. wet vac on the open vent maybe ?
 
heatservice said:
My thoughts would be the coil could have a high point where air has been trapped, not such a problem with a fully pumped system. wet vac on the open vent maybe ?
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The Coil will naturally rise to the flow tapping inside the cylinder, and looking at the photo there appears to be a 22mm vent rising from there, so unless that is blocked, (need OP to do the magnet test), I cant see the coil being air locked. Gravity primary flow should rise constantly from boiler to where it bends over back into the F&E cistern purposely to vent the system.

GoodOne, looks like you need to replace the pump, hopefully the clock will be ok once power is restored. You're now sure there is not a motorised valve on the primary return, so then please try the magnet test. I think using a wet vac on the vent may well draw water out, but if then if the pipe is clear anyway, any air should have vented out when the system was refilled.

If, as I suspect, there is a physical blockage somewhere in those primaries, it will not shift that in a month of Sundays. The only solution is to cut out and replace the affected section of pipework.
 
In the days when gravity HW systems were common I had many that airlocked when refilling, sometimes a gentle shaking of the cylinder would be enough to remove the airlock. Or if you isolated your heating system by turning off one of your pump valves along with both upstairs & downstairs balancing gate valves then using the boiler drain cock flush the primary pipework, might be worth a try if those gate valves & that drain off are OK.
 
Could also try connecting mains fed hose to the drain point and forcing water back up the system into the F&E... this might push any blockages away from bottlenecks and disperse them so they can then make it back through.

BUT... make sure your overflow is functioning at the F&E and would be good idea to have someone up there (with a mobile phone) whilst you’re manning hose down below.
 
You said you got a strong jet of water from the toilet radiator when you bled it, try bleeding it with only one of the valves turned on at a time and see if you get the same from both flow & return.
 
Thanks guys for all the supports. I'am doing it one at a time now. Btw just replaced the pump. Can I turn it on before fill the system with water, just to try if there any shot circuits again
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Tested the pump, they are good.

I filled the system up and turn on the HW and it fired up. I touched all the pipes by the boiler after about 5mins, the only part that gets really hot is the pipe below the pump (same as the picture with the red box). So, I turned off the HW.

After about 5mins I turn on the HW again, but it didn't fire up though I could still see the pilot light. Then I try to turn on CH & HW but it didn't fire up.

Well, now I will try to troubleshoot the blockage or airlock as all the advice.
 
Boiler will fire, but if there is no circulation to take the heated water away from the boiler, it'll soon switch off again. I would have expected it to fire up again though once CH was switched on, as the pump should be moving heated water away from the boiler quite quickly. Find the issue with that gravity circuit now before doing anything else, get that working properly, and then worry about the CH.
 
Couldn't you feel any heat in your primary flow, the 1" (28mm) pipe that comes off the left hand side ?
 
heatservice said:
Couldn't you feel any heat in your primary flow, the 1" (28mm) pipe that comes off the left hand side ?
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Sorry, I turn on the HW for 3mins again this morning, just to make sure which pipe has heat. I could feel the heat on the left-hand side aswell.
 
I'd expect heat to travel a little way from the boiler, along both gravity primaries, even if there was no circulation. Once up to temperature though it's surprising how quickly gravity circulation moves when its operating as it should. Fire the boiler up (with CH off) and see how far up the pipe the heat gets. An air lock would likely prevent complete circulation, whereas a blockage may allow a slight amount of water past, (unlikely it would block completely overnight), which may help with a diagnosis for the location of the problem.
 
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