I've recently drained down heating system for maintenance. After refilling, venting and adding inhibitor the heating is working fine. However, I now cannot get the hot water to work. Water just dribbles out of the taps and very hot. I followed the fault finding flow chart in the manual and have replaced the usual culprits, namely DHW flow switch & micro switch and the DHW frost/limit thermostat. Still the hot water doesn't work. Any suggestions would be useful as i'm beginning to smell!
potterton puma 80 - no hot water
- Thread starter Gavinth
- Start date
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is all the isolation valves or stopcocks open
Yes, all valves open including mains stopcock. Reading other similar posts it seems the red LED indicator is important. When I open a hot tap the red LED is NOT lit, hence why I replaced flow switch.
Have you adjusted the switch correctly so the pin from the flow assembly actuates it?
Are the switch wires connected to the two outer tags?
Have you looked carefully at the board for broken joints on the connector pins?
Are the switch wires connected to the two outer tags?
Have you looked carefully at the board for broken joints on the connector pins?
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I replaced the flow switch and microswitch exactly as it was with a 5.5mm gap as indicated in the manual. Switch wires are connected. Not checked board though. Will do so this evening. DHW & CH were both working fine before drain down, so I am mystified what could have caused problem. When I tried the hot water after refilling it got extremely hot as the very low flow must is picking up heat from opeeration of boiler for CH. Are there any high temp resets for example on these boilers?
With the type of heat exchanger on this boiler you will always get an initial very hot slug of hot water if the heating has been on and set to maximum temperature.
AFAIK there are no overheat stats or sensors that would stop the LED coming on for a demand.
Is there a sufficient flow of water to actuate the switch - can you hear it operating (clicking).
AFAIK there are no overheat stats or sensors that would stop the LED coming on for a demand.
Is there a sufficient flow of water to actuate the switch - can you hear it operating (clicking).
Thanks. Hard to tell because nearest tap not that close (am on own). Normally when I turn on a hot tap I can hear the boiler fire up almost immediately. Now there seems to be nothing but a slow trickle of water. You seem to be suggesting there is not enough mains flow to set the controls in motion. I'll systematically check all conns, valves etc again just to make sure.
Thanks - I've been away 10 days so just seen reply.
I set switch distance same as replaced unit but I guess new one could be different - hard to tell, but I'll adjust as you suggest and see if any difference.
As with a previous response, I don't think the switch actuates because there is no audible click when a hot tap is turned on.
Presumably, to manually operate the switch, I have to uninstall from switch and push the switch mechanism with the cables still attached? Then I should see a red light?
I'll try again tonight and let you know.
I've checked the points previously raised.
The microswitch when depressed activates the red LED.
However, if I detatch the locking nut and insert the microswitch fully into the flow valve/switch the red LED is permanently activated. If I install with the locking nut between the 5.5mm and less then the red LED does not light up.
There is still a trickle of water from any hot tap which leads me to believe it is a water flow problem. I've checked the cold water main and the valve to the boiler is open. The quick fill does what it is supposed to so there is pressure there. I have plenty of pressure and flow from my cold mains taps. The hot valve from the boiler is open and sure enough it leaks when closing! Is there any other device in the loop that could be restricting flow?
I'm almost at the point of boiler replacement which seems a great shame when the heating is working fine.
The microswitch when depressed activates the red LED.
However, if I detatch the locking nut and insert the microswitch fully into the flow valve/switch the red LED is permanently activated. If I install with the locking nut between the 5.5mm and less then the red LED does not light up.
There is still a trickle of water from any hot tap which leads me to believe it is a water flow problem. I've checked the cold water main and the valve to the boiler is open. The quick fill does what it is supposed to so there is pressure there. I have plenty of pressure and flow from my cold mains taps. The hot valve from the boiler is open and sure enough it leaks when closing! Is there any other device in the loop that could be restricting flow?
I'm almost at the point of boiler replacement which seems a great shame when the heating is working fine.
Would be at rear end of part 64. Last one I did was a combi 80 so possibly slightly different. Apart from isolating and draining, 5 minute job so worth checking. Make sure you have the appropriate washers, they are boiler parts and not in standard washer boxes.
Thanks for all your advice but I'm getting so frustrated!!
I definitely have cold water through part 98 to 64 at 84 (if that makes sense from the previous parts diagram) The restrictor on 98 is fully open counterclockwise - I have not altered this ever. There is definitely CW pressure to the flow switch 110 and through it. However, when everything is back in place it's the same old story. A trickle of hot water from any tap. Still the red LED does not light (only when manually activated or permanently when microswitch screwed completely into the flow switch).
It just seems to me as a layman that something is preventing release of hot water from the boiler but I cannot see what I have done when draining down the central heating that could cause it. Oh well, if all else fails I'll have to get one of you experts to recommend a new boiler and installer, but I'm determined not to give up just yet.
I definitely have cold water through part 98 to 64 at 84 (if that makes sense from the previous parts diagram) The restrictor on 98 is fully open counterclockwise - I have not altered this ever. There is definitely CW pressure to the flow switch 110 and through it. However, when everything is back in place it's the same old story. A trickle of hot water from any tap. Still the red LED does not light (only when manually activated or permanently when microswitch screwed completely into the flow switch).
It just seems to me as a layman that something is preventing release of hot water from the boiler but I cannot see what I have done when draining down the central heating that could cause it. Oh well, if all else fails I'll have to get one of you experts to recommend a new boiler and installer, but I'm determined not to give up just yet.
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