Thermal store installation

[m550344]

I recently have installed a thermal store replacing a leaking vented cylinder. It is normal when heating the tank that I can expect overflow into the f&e? I assumed this was the case after reading many threads about the need to ensure existing tank can cope with increased expansion requirements.

 

[Bernie2]

Err!

Sure a thermal store heats more water, and hot water expands, so you need more space to store the expanded water. Its simple really.

The old expansion allowance was calculated probably for a much smaller cylinder and so less hot water and so less expansion space required.

 

[m550344]

My question was more around understanding the operational aspect of a thermal store and that it was common for the store to dump hot water into the F&E large amounts of heated water after less than 10 mins of a heating cycle kicking in. I originally went by a F&E tank capacity calculation that I found on a forum, based on cylinder size and no. of radiatiors but have come to the conclusion my existing tank needs replacing as the calculation was flawed, or the existing system venting setup is not correct.

 

[Bernie2]

I would suggest going on to the Gledhill "Torrent" site and downloading the installation manual. It gives you some clear ideas. Its just that it can take a while for me to explain and they have already done it.

But if you need more specific info please feel free to ask and come back on.

However it should not be venting over into the F &E tank. Probable cause is the vent may be too low.

To give you some ideas:

If you heat water from say 4C to 100C it will expand by about 1/25th in volume. The water in a meter length of pipe if heated the same would expand by 40mm.

Using that as a base measure 40mm is allowed over the cistern water level for every 1 meter height of the system. I.e from the bottom of the heat store to the water level in the F &E cistern.

So if that is 5 meters say, then its 5 x 40mm = 200mm over the water level to the start of where the vent hooks over the cistern. Then add another 150mm so its really 350mm.

Part of the thinking is: Because the water in the F & E cistern is colder than the water in the vent the water levels will be different.

You also need to make sure the vent does not discharge over the ball valve and its end is as high inside the cistern as possible.

 

[david williams]

gledhill have specific requirements for installing thermal store not compling with them leads to problems.always read the paperwork.how high above thermal store is f@e tank

 

[justlead1]

Hi, Before getting to involved bend the arm or adjust ball valve so as the level when cold is reduced. The extra volumeand reduced hight gained may help. Good Luck