Coil Indirect Cylinder, I get heating but no hot water out

Postby RFindlay » Wed Jul 22, 2009 9:48 pm

I have a Coil Indirect Cylinder fed by a Baxi back boiler, from what I can tell the cylinder gets a hot feed from the boiler (my heating system works well).

I can't be shure whether the valve atached to the return flow from the primary circuit is operating correctly, can anyone suggest an easy way of checking it, or think that there might be something else that could be the problem. The hot water stopped when I turn the tap from the water feed tank to the cylinder off and then back on a couple of hours later (the hot water system was turned off as well).
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Postby Dave From Leeds » Thu Jul 23, 2009 10:11 pm

When you say that you turned off the tap from the water feed tank to the cylinder, which tank do you mean? You should have two for an indirect system as you have described. The larger one is the cold water storage tank which tops up the main body of the cylinder when you draw off hot water. The smaller tank is the Feed and Expansion tank which keeps the central heating system and the heating coil inside the cylinder topped up. If it is this second one that you turned off the supply from for two hours then you may have generated an airlock in the coil within the hot water cylinder which would stop the gravity circuit through the heating coil and the boiler.

The easiest way to clear an airlock as described above is to find two pipes going into the side of the hot water cylinder one above the other. Then undo (but do not remove) the union connecting the top one of these to the cylinder. This should release any trapped air in a similar way to opening a radiator bleed valve.

Regarding the valve whose operation you are unsure about, is this some sort of automatic valve that allows you to run the central heating without heating the water? If so and it is failing to open this would also prevent the gravity feed circuit through the cylinder heating coil from working. As for how to check the valves operation, I have no idea, not being a plumber but just a keen DIYer whose system doesn't have any automatic valves! I'm sure there are others on this forum who can help though.
Dave From Leeds
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