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Hot Water Entering Central Heating F and E Tank in Older Property

Postby ahealy » Thu Jan 14, 2016 11:15 am

Excuse the long explanation here, and potentially my ignorance! We are completely novice DIYers...

We have recently moved in to an old house and are having some central heating issues.

In place is a mains connected cold water system thorughout the whole house, unvented tank for hot water (megaflo) and an open-vented central heating system. We noticed that a lot of the radiators were not heating up so went in for mega bleeding session throughout the house (three floors due to converted attic).

All seemed fine until the next time the heating came on, when some of the radiators started making some quite extreme gurgling noise. Our assumption was air in the system. Went in to the remaining attic space and the F&E tank was very empty and not reaching the outlet pipe! The float has clearly been replaced in the not distant past, as the old one was next to the tank, and there was also a milk bottle "vessel" which we can only assume was being used to manually top up the tank. The stop cock valve doesn't seem to be working, so we assumed that is the problem, and that the CH system was sucking in air rather than mains water to top up, hence the noise. So first two questions:

1. Can we assume we have a leak in the CH system? We have no obvious damp patches, so how do we find it?! Or could it be because we bled the radiators and so a lot of water was sucked back in to the system (although the "vessel" suggested the previous owner had had the sane problem)?
2. How do we go about fixing the stop cock valve?

We topped up the tank manually to a few inches deep (an inch over the outlet) and left it. We have also turned three out of 12 radiators off. This morning the heating came on no problem, but I noticed a running water noise coming from the attic. Queue panic that the tank was overflowing! Fortunately it wasn't , but there was a steady stream of hot water coming out of the vent pipe (the one hanging over the tank). This stopped soon after the CH went off. Next questions:

3. Is this because I put too much water in to the header tank when I manually topped it up manually?
4. Could it be because some of the radiators are turned off so there is too much heat in the system?
5. Do we have a buggered thermostat?

Final question - have I got the set up of the system right, i.e. that this doesn't have anything to do with the megaflo?

Apologies again for the long post and thank you in advance for any help. We do have a professional coming in next week to look at it all but would like to have an idea of the potential problem before being ripped off!!
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