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Expansion Vessel Upside Down?

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Discuss Expansion Vessel Upside Down? in the Central Heating Forum area at Plumbers Forums

H

hallra

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Hi,

Has this expansion tank been installed upside down?
- The cold water expansion tank is install this way as well...

Or is there something special about the configuration that I haven't understood?

Surely air gets trapped with the expansion tank fitted this way?

I still have noise in my top radiators, I am bleeding everyday and I'm scratching my head trying to find the cause.
- FYI: An Air Seperator is on order.


photo2.jpg
 
Hi Harvest,

Thanks for your reply.

Yep it is on the heating side.

I don’t understand then, how does air not get trapped, as the expansion tank is on a long run of pipe work, with it being the highest point.
 
You're getting confused with an open vented header tank I think. With a bottle like this there should always be air in the bottle. The normal issue with these though is that the air pressure in it is not maintained correctly and should be checked annually at least. As the pressure in the tank increases and the water expands the expansion pushes into the bottle which has an air pocket in it, when a tap is opened any water in the bottle gets pushed back in to the system. If the air pressure in the bottle isn't maintained then this bottle can be completely full of water and when the pressure in the system increases the water has nowhere to go and the pressure relief valve at the bottle will open to get rid of the pressure. The problem then is that they normally never close properly and need to be replaced.
 
Sorry I didn’t explain myself properly.

There is a diaphragm within the expansion vessel, one side has air, the other side, the system side, has water.

The point of the air side is to allow the expansion of the water on the system side, without a significant pressure increase.

My question was what if air was trapped on the system side, therefore air on both sides of the diaphragm, would this cause a problem?
- Air would presumably be trapped if the system has been emptied of water and then refilled, as there is no way of bleeding that part of the circuit, as only one pipe to the expansion vessel.
- I know there is another pipe but that route is blocked by the safety value.

I’m asking these maybe dumb questions as I’ve got a lot of trapped air in the sealed heating system that should not be there and I can’t work out what the cause is.
- I’m bleeding daily two radiators upstairs and they constantly have good amounts of air in them very soon after they have bleed, as a consequence there is a lot of noise being produce.

I have tried many things to resolve and still I have a problem, next try is an air separator.
 
Yeah I know, I’m clutching at straws, this has been going on for weeks and I’ve tried so many things I’ve got desperate.
- I’ve had a plumber look at it who couldn’t find anything wrong.

I’ve just had an email from someone at Altecnic, they have offered to talk through the problem in detail with me to see if they can work out the cause.

- A lot of the system components are from Altecnic/Caleffi, so I had sent them a speculative email.
 
The expansion vessel won't be the source of your problems, any air that does end up in it from the CH water doesn't cause any issues as it acts in the same way as the air behind the bladder, there's no way you'd get enough air in there to alter the performance of the vessel and it wouldn't cause any noises.

With regards to the having to constantly bleed your rads, is this a new system? Have you had any alterations made to an existing system? Has an inhibitor been added?
 
I am going to contradict the thinking a little by saying that a heating system vessel ideally should be fitted with water side upmost.
Many diagrams also show them fitted with water connection upmost and straight into heating pipework, or if a high spot then an auto vent shown fitted.
But it doesn’t seem to matter which way you install them
 
I was told by an agent who supplied all types and sizes of expansion vessels that the colour has nothing to do with the type of vessel.
I do remember they supplied a potable vessel to me that was red, - identical in colour to heating system vessels.
Never seen that again though.
The large stainless steel flange on some of the potable vessels is a giveaway.
 
White, Blue, Grey & Silver (stainless steel) = wholesome / potable water usage. (or so it use to be)
Red = Heating (or so it use to be)

It was all to do with the type of rubber used, I seem to remember that natural rubber was used in potable as it didn't support bug growth but they couldn't handle high temperatures so neoprene was used for heating.

My understanding is the same as Best, manufacturers (some at least) are moving over to red for everything because of the newer types of rubbers used, so we will all need to start checking the reds on potable systems before condemning the original installer.
 
Constant air ingress is sometimes caused by a poor seal on the vacuum side of the pump. I think I've posted this before but I did an experiment with some clear hose connected to a circulating pump and put in a fibre washer with a scratch across it on the vacuum side of the pump. Whilst it never leaked water it did show a stream of bubbles being pulled into the system when the pump was running. This air would then usually move to a high point e.g. upstairs radiator. The air ingress was stopped by the installation of rubber pump washers.

I made this setup in the workshop because someone did not believe air could get in at the pump without showing a leak when the pump wasn't running. I proved it can! Worth a look checking the washers at the pump, tighten them if possible or replace them with rubber ones if they aren't already. It's worth a try!
 
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