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Author: Subject: Central Heating Advice
Surrey Dave

posted on 28/12/11 at 12:40 PM Reply With Quote
Central Heating Advice

My parents have a Trianco oil fired boiler, there is no control on the water temp,therefore it gets very hot.

Lately we have noticed water coming out of the overflow when the boiler is running, I have checked the ball valve in the heating tank it drips but not enough to over flow significantly.

Therefore I'm assuming that the tank is back filling from the heating system , is this ok /normal when the system is being used more continuously at this time of year?

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hughpinder

posted on 28/12/11 at 01:00 PM Reply With Quote
I thought all boilers had to have a thermal cut out, even if you cant adjust it?
If the water is flowing out of the overflow, either the float valve is letting in water when the tank is cold, so its full up to the overflow pipe and starts to overflow as soon as you heat it, or the boiler is actually boiling (may be local boiling in the boiler, like if the circulation pump fails) and the steam is forcing the water out of the overflow. I managed to overheat my solid fuel boiler once, and the plastic float partially collapsed, and then used to pass water into the header all the time as it wan't as bouyant (they aren't supposed to be in boiling water). I put in a copper float in my latest install (about £15-20 for a copper float)
Regards
Hugh

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adam1985

posted on 28/12/11 at 01:18 PM Reply With Quote
If its a indirect system the coil in the cylinder could have pinholed causeing it to fill from
The dhw side

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Stott

posted on 28/12/11 at 03:51 PM Reply With Quote
I have a direct combi and it also had the problem mentioned above but my water to water heat exchanger pin holed and filled the tank from the mains.
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ginger ninja

posted on 28/12/11 at 04:09 PM Reply With Quote
Discharging water from the overflow is not normal or desirable. The heating system should have an additive in the water to help prevent scale and corrosion. If you are losing water everytime it heats up, and consequently replacing this with clean untreated water when it cools down, then the inhibitor will be diluted to the point where the system is likely to be corroding internally.

Water expands as it is heated. This expansion / increase in the system volume is catered for by allowing the water to rise and fall in the header tank, or by an expansion vessel with pressurised bladder in a sealed system (as in a car engine cooling system).

If the water discharging from the overflow is not continuous, it is likely to be the excess water as a result of expansion which the tank cannot accommodate. This could be for a number of reasons. If it has only started doing it recently, think what might have changed. If the float valve is letting in too much water when the system cools down, then there will be less space available for the expansion water. This could be as a result of the valve is not closing properly, or the float has a hole in it etc.

If you are unsure please have someone look at it that is, but either way, if the problem persists it could result in a costly repair.

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