trapped air - no escape?

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Old 01-08-05, 09:45 AM
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Question trapped air - no escape?

hi, can anyone tell me how to bleed air from the inside a domestic hot water system which has no bleed valve? Possibilities I have tried so far are: a0 temporarily removing thermostat from boiler in order to superheat boiler in the hope that the exceptionally hotter water will force itself through the sheating spiral inside the indirect hot water cylinder and carry the air out with it; and b) contually stopping and restarting the hot water circuit by turnung on and off the thermostate strapped to the side of the hot water cylinder, thereby hopefully incihng airbound water up an expansion pipe into the expansi9on tankl where hopefully the air can escape.

Neither of these seem to have worked. Has anyobe se any more ideas please?
 
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Old 01-08-05, 02:59 PM
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Some of what you described is not clear to me, but I will advise against the superheating idea as serious boiler and personal damage could occur. The domestic water is the water you use for showers, washing machine and all faucets. Is that the water you meant? Also the thermostat strapped to the water cylinder is not clear. Could you try again to explain the situation?

Ken
 
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Old 01-09-05, 09:24 AM
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reply to Loyal to oil re no escape

Hi Loyal to oil. Thanks for reply.

My heating is an indirect system wherein fluid (=water containing additives) is heated by a boiler and is then passed via pipes to a heat exchanging spiral/coil inside a water tank which is fiull of mains water. The fluid is kept separate from the water inside here because it is still kept in its pipes in this spiral inside the tank. It gives up its heat to heat this water inside the tank which then becomes hot water for the bath and faucets etc. After leaving this tank it then passes to a valve where it has the option of either returning to the boiler or going to the radiators first if needed and then going back to the boiler.

Thus the hot water is heated indirectly by the action of the fluid that is kept separate from it. There is an airlock in this fluid system such that it seems that most of the spiral/coil in the hot water heater tank is jammed with air. There is no bleed valve in the system but there is an escape tube up into an expansion tank upstairs, but this tube is positioned outside the tank on the pipes going to and from it. I need to move that air. Superheating is a possibility, but I agree superheating has its problems and I've only attempted it for short periods on the advice of a plumber.




Another possibilty is this. There is a sensor which acts as a thermostat and this is strapped to the outside of the tank. Its job is to measure the temperature of the water in the tank and advise the control panel whether to turn the boiler on to heat up the fluid to exchange more heat into the hot water system when I've used a lot of it in the bath etc. I have been advised to turn the thermostat on and off to inch the water / air along inside this coil by making the pump pulse on and off and seeing if that nudges the air along with it. So far this hasn't been successful either.


I hope I have explained this better now. Have you any suggestions?

thanks
 
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Old 01-09-05, 04:54 PM
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Now I get it. What you have is not too uncommon. When an indirect water heater has its coil supply and return connections on the bottom, there is no good way to get the air out. If the circulating pump pushes water through, it will push the air out too. It can be purged out if the pump is on the return or if the pump can't do it alone. All that takes is a valve to isolate the return line from the boiler and a drain valve on the tank side of the isolation valve. Then you can purge it as if it was a heating zone.

Ken
 
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Old 01-14-05, 02:03 PM
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thanks K

I'll have a good think about that and maybe get a plumber to fir me some valves

cheers

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