I have a problem that has just occured. When the CH pump is running there is a continuos trick of water from the expansion overflow into the CH heater tank. Is there a standard fault that can cause this?
The usual cause is simply that the water is far too hot, which is exactly what the expansion pipe is for. I assume the CH system is bled properly though ?
The vent pipe (one that rises beyond the height of the water level in the cistern) will only run if the boiler thermostat has failed. You would know about this as the noise is similar to an earthquack.
Water dripping from this pipe could be due to several reasons. Normal operation will not be one of them. Raising the loop is not the answer either.
For my money it will either be a blockage in the feed pipe or bad plumbing that is causing pump over to take place. Only answer is cut and correct.
It depends on the height of the vent over the tank though. I've seen them just bent over the edge of the tank and with the water level too high to start with it can cause a problem.
It depends on the height of the vent over the tank though. I've seen them just bent over the edge of the tank and with the water level too high to start with it can cause a problem.
If the system worked once, then raising the vent is not the cure. I agree with DP, it's likely to be the feed pipe blocked. This should be checked first.
At one time the flow and return on a fully pumped system were plumed as follows.
The flow pipe out of the boiler had a 22 branch that rose continiously to the F&E cistern and a short distance above to do a 180 degree to be in a position to discharge (if need arose) into the F&E cistern. Similarly, the return just before it connected to the boiler was fitted with a tee branch of which was known as the feed connection rose to connect to the F&E cistern to feed water into the installation. Pumps use to be on the return. The vent (due to boiler internal resistance was always at a lower dynamic pressure than the feed pipe therefore no pump over taking place.
Another format is the one where the feed is connected within 150mm after the vent pipe followed by the pump. Here the pump sucked on both pipes therefore again no pump over.
A gravity HW zone has the vent and feed connected to the flow and returns at the cylinder. Quite often the gravity HW zone gets converted to fully pumped often resulting in pump over taking place because the system does not get modified accordingly.
If the three tee rule is observed, pumpover will never take place. Also if manufacturers instruction for pump installation are observed, pump over should not take place.
I understand what you say DP and agree with you but there are a lot of council houses where I live which were built with a fully pumped system where the vent comes off the feed to the top of the coil and the make-up tank connected to the bottom of the coil. These houses are now nearly 30 years old and I've experienced the flow through the coil being severely reduced by deposits, perhaps because no inhibitor was used for years. The result is that when on HW the pump, which is on the flow side from the boiler, can find it easier to pump water from the make-up tank and through the vent because that circuit has a lower resistance.
This is because the system was initially gravity HW/ pumped CH.
The three tee rule is broken resulting in pump over. If you look through installation manuals, you will note that a pump can never be in the feed/ vent loop.
A council can also make mistakes. Some areas in Glasgow are fitted with backboiler but ventillation was not installed. This was done at a later stage when someone flagged the omission.
I have in my time seen some strange pipe runs on the vent when simple approach of connection at the correct point in the installation is the answer not overlong pipe runs. Water sonverts to steam by a factor of 1600. One has to get rid of this at the vent ASAP when she blows her top.
I understand what you are saying DP, ok for gravity but when a pump is added the vent and make-up connection are on opposite sides of the pump. Thanks for advice.
If you need to find a tradesperson to get your job done, please try our local search below,
or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Please select a service and enter a location to continue...
Are you a trade or supplier? You can create your listing free at DIYnot Local
