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Assistant tank of vacuum tube solar water heater

Assistant tank of vacuum tube solar water heater

Assistant tank of vacuum tube solar water heater

(OP)
We have a 300l tank solar water heater installed with an assistant tank. Please refer to link below for model of solar water heater.
http://www.ousunsolar.com/en/products.asp?pid=18

The assistant tank's purpose is for automatic filling of the 300L non-pressure tank. When the 300L tank is full, water rises in the assistant tank and closes the valve on the in incoming supply pipe.

The problem we have us that the ballcock in the assistant tank expands and water is getting inside. (This is not supposed to happen) Since the ballcock gets heavy, it no longer closes the valve. Hence we are having overflow problem.

This is the first time that we have such a problem. Can anyone explain to us why water is getting inside the ballcock as physically it is a sealed body?

Also I suspect the assistant tank volume which is about 3L is too small for a 300L system. Since the water in the 300L tank gets heated up and expansion volume from 20 deg to say 70 deg will be more than 3L, there is a built-up of pressure inside the assistant tank. Does this make sense? Could this be causing water ingress inside the ballcock?

Amy ideas on what could be happening would help us a lot.

Thanks

RE: Assistant tank of vacuum tube solar water heater

A ball cock is the whole valve assembly. A float that is filling with water has a leak in it. It is defective and must be repaired or replaced. The drawings in the website are probably not very accurate regarding that actual piping lay-out.
Hot water should come from the top of the storage tank and cold water added at the bottom (just like a domestic water heater). "Assistant tank" is probably a poor Chinese translation for expansion tank. If you have much plastic pipe in your loop, then three liters may not be large enough. The only way for pressure to build in your expansion tank is for the vent line to be plugged.

RE: Assistant tank of vacuum tube solar water heater

such floats are notorious for developing leaks.
Especially if they are cheap Cu plated steel ones.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

RE: Assistant tank of vacuum tube solar water heater

"the ballcock in the assistant tank expands and water is getting inside"

Or it has a leak, like Ed/CP said. If this is a hollow metal float, replace it with a block of polyethylene foam (or epdm foam if you can find it).

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