Expansion vessel on unvented system is hissing

[CNelson]

I have an unvented system in my home. The fitters that installed it recently came back to replace the expansion vessel as it kept hissing. They said it was a fault with the seal on the expansion vessel. Unfortunately, the new expansion vessel is still hissing.


It sound like boiled water hitting a cold surface, with some gurgling sounds. But predominantly hissing.


When I put the heating thermostat up high for any length of time then switch it off, that's when the hissing happens.


The tundish is dry.


However, the pipe from the expansion vessel to the tundish feels hot.


Can anyone advise about this problem?


Thanks very much.


-CP

 

[Dotty]

I assume you checked they were g3/unvented qualified?

There's nothing you can do on this.

Check that they do have g3 and get them back. If they don't then demand someone who is as they are placing your lives in jeopardy.

 

[albatross]

Take a photo. It sounds rather odd.

 

[Ermintrude]

A photo with annotated hiss please

 

[kay-jay]

What colour is the offending vessel?

 

[TBServices]

What colour is the offending vessel?

Red would be my guess 😉

 

[kay-jay]

Red would be my guess 😉

Aah yes the cider red wine and ale has conspired against me fully reading the op......

 

[happyflyer]

I doubt the hissings coming from the expansion vessel, there's nowt in there to make it hiss, bet there's an AAV next to it that's hissing, where are the photos, need them, you see you got me guessing now, red, blue,white....snake coloured..send the photos.


https://www.google.co.uk/search?q=p...ecnic%2Faltecnic-expansion-vessels%2F;495;296

 

[CNelson]

Here's a picture. The expansion vessel is a zilmet.

 

[happyflyer]

I don't think you could distinguish anyone particular noise in that area, there are so many elbows and the pump is so near there will be lots of noise that sounds like a snake, the whole plumbing job is a complete mess, pump impossible to get at , electrics hanging lose on a board, wish you hadn't sent the photo now, there is just one item there that makes me shudder, two 15 mm couplings(sockets) within 6" of each other, what has the world come to!!! Its been throw in, the plumber needs to go to Specsavers, sorry I can't help it, it's a very low standard. I can't see any pressure gauge for charging???

 

[kay-jay]

I don't think you could distinguish anyone particular noise in that area, there are so many elbows and the pump is so near there will be lots of noise that sounds like a snake, the whole plumbing job is a complete mess, pump impossible to get at , electrics hanging lose on a board, wish you hadn't sent the photo now, there is just one item there that makes me shudder, two 15 mm couplings(sockets) within 6" of each other, what has the world come to!!! Its been throw in, the plumber needs to go to Specsavers, sorry I can't help it, it's a very low standard. I can't see any pressure gauge for charging???

I can see the guage. Its connected to the prv below the exp vessel.

Looking at the pic its probably the air release valve

 

[happyflyer]

yes got it I need to go to Sepcsavers

 

[kay-jay]

looks like its stood on 2 bits of 2x1 instead of a solid base

 

[chris watkins]

Its a bubble top so problem is with the red vessel on the sealed heating system, get them back to set the the vessel charge to that of the static head pressure / cold fill.

P.S. Two couplings on a 15mm safety valve discharge, the end of the world is here !!!

 

[IDCHAPPY]

So that's the expansion vessel for the heating system then?
Probably the Air eliminator as said before 🙂

 

[CNelson]

An engineer came to take a look at it today and heard the noise. The expansion tank is a bit too big for the system, it is currently 18L. It needs a smaller one.

thanks for the responses.

 

[happyflyer]

Is that it, why didn't we spot that,Doh!!!

 

[Dotty]

An engineer came to take a look at it today and heard the noise. The expansion tank is a bit too big for the system, it is currently 18L. It needs a smaller one.

thanks for the responses.

Rubbish! I've never heard of issues with a slightly (which yours is) oversized expansion vessel. Undersized, yes. Oversized, never!

Bet the vessel pressure was incorrectly set!

 

[chris watkins]

An engineer came to take a look at it today and heard the noise. The expansion tank is a bit too big for the system, it is currently 18L. It needs a smaller one.

thanks for the responses.

It does not need a smaller one !!!! You can not over size an expansion vessel, trust me. It is the charge pressure that is wrong.

 

[mutley racers]

Rubbish! I've never heard of issues with a slightly (which yours is) oversized expansion vessel. Undersized, yes. Oversized, never!



Bet the vessel pressure was incorrectly set!

I thought I was going nuts. Thinking how come I have never heard this before. Thanks for clearing it up crops

 

[SimonG]

I just fell off the couch laughing.

 

[happyflyer]

Simon me too:30: smaller smaller smaller my eye!!!!


If you want to go over 100 Deg C you may need a bit more pressure, but not on a domestic, OP will be back next week under another name, Title "My Safety Valve is leaking water"

 

[kay-jay]

I still reckon its the air relief. ...🙄

 

[IDCHAPPY]

Biggest load off tosh I've ever heard, it's like saying your winkle is too big :lol:

 

[happyflyer]

I still reckon its the air relief. ...🙄

I have that after a good Ruby!!!!

 

[happyflyer]

Toshville:banghead: my career is in tatters, I have just wasted the last 50 years of my life, dress making for me now

 

[Dotty]

Biggest load off tosh I've ever heard, it's like saying your winkle is too big :lol:

An affliction I've never suffered.

Sadly.

 

[happyflyer]

An engineer came to take a look at it today and heard the noise. The expansion tank is a bit too big for the system, it is currently 18L. It needs a smaller one.

thanks for the responses.

Nelson, do you get the distinct impression that your man has just opened a can of snakes, how long did it take him to come to the conclusion it was too big ???

 

[Ermintrude]

Only g3 he's got is his phone in the mirror 3G!