Mystery Object - AAV?

[Twinker]

A strange object has been found fitted at the back of a boiler feeding a fully pumped 27 year old vented heat only system. Water dripping from this device is a hazard as it can enter boiler electronics.

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But what is it and can it just be removed and replaced with a blanking plug?

It is fitted on an unused flow connection, where a blanking plug is expected. It is not part of a circuit and does not feed another component or pipe. There is a ring of holes which weep water even when the system is cold. The end cap can be screwed down against a spring onto an adjustable stop ring.

If it is an AAV (or ultra low cost pressure relief valve) its location at the back of a boiler where drips can enter electronics seems bizarre. Was that OK even in the 80s?

Any help appreciated.

Thanks

 

[45yearsagasman]

That's an old style pressure relief valve.If your open vent terminates over the expansion tank then the old valve can safely be removed and plugged.

 

[Onetap]

I think it is a spring-loaded pressure relief valve. I'd fit a new PRV and pipe the discharge to outside.

 

[spraggo]

It is a spring safety relief valve that used to be fitted as standard on old solid fuel boiler circuits, they are now obsolete. You will need to remove it and fit a 3/4 brass plug in it`s place if it is leaking.

spraggo

 

[Nige F]

or a 3/4 black iron plug or maybe a 1/2 inch one

 

[expertgasman]

I think it is a spring-loaded pressure relief valve.
YES, it is

I'd fit a new PRV and pipe the discharge to outside.

NO, don't. Refer to other posts.

 

[Twinker]

Thanks all. I've started the free the rusted and useless PRV task with Plusgas and Loctite freeze & Release.

There is a vent tube over the Expansion tank. Lets hope its not blocked......


Brian

 

[45yearsagasman]

I hope you remember to drain or bung the system,otherwise youll get a bit damp

 

[Twinker]

What and miss out on a new water feature?

I had the wjhole system down today to clean rads (even X800 for two days left enough magnetite to fill a bucket).

Is it OK to use an old gas type tapered iron plug; I left the iron 3/4 to 1/2 inch adaptor in.

 

[Nige F]

that plug is fine - use ptfe ( I know you haven`t got hemp+ paste )

 

[Twinker]

Good; I used PTFE (last half of the threads only)

Now that I know it was a PRV, perhaps I'm wrong in my other guess about sucking in air. I have a top floor rad where I'm bleeding air out, but without the expansion tank ball cock complaining and topping up the tank.

Could it be though, that the weeping PRV was the culprit - I'll know when I'm done cleaning rads, or my wife says she can't stand a cold house any more!

This mght need a new topic, but my cold feed pipe is connected from the F&E to the cold return right by the boiler. Most modern example drawings say the cold feed should be just upstream of the pump and downstream of the vent.

Could the non-standard postion affect performance in any way?

Thanks for your help,

 

[Onetap]

I think it is a spring-loaded pressure relief valve.

I'd fit a new PRV and pipe the discharge to outside.

NO, don't. Refer to other posts.

Why not, Mr. Expert? Is a new £5 PRV too expensive?

Here's a clue as to why I suggested replacing it; PRVs will often start dripping AFTER THEY HAVE OPERATED.

Not one of those who have suggested removing it and plugging the hole have suggested testing the 27 year-old open vent and cold feed pipes.

The advice above stands.

There is a vent tube over the Expansion tank. Lets hope its not blocked......
Brian

Yes, Brian, you do that.
One would normally expect any air (or gas) in a heating system to be discharged from which pipe?

 

[Onetap]

There is a vent tube over the Expansion tank. Lets hope its not blocked......

A question, if I may Brian.

The open vent pipe; is it insulated?
Could it possibly have frozen in the cold weather we had in the past couple of months?

 

[45yearsagasman]

Talk about making a mountain of of the proverbial.The standard remedy for old leaking PRV's on open vented systems that is to plug them off.
END OF

 

[Twinker]

Your point about the vent pipe (and the PRV) is well made.

I know the vent pipe is insulated. I will check it though.

I've certainly had the F&E cold feed blocked with magnetite. The same fate could have occured to the vent. The cure is to cut and replace.

May I ask one question, do modern boilers have a PRV function included?
I ask because I will need a new boiler soon. My old, and rather tired, Netaheat 10/16 is very basic and perhaps that's why the original installers fitted the PRV. The installation notes for the old boiler do not call for it; though I'd prefer such a device (if needed) to be fitted in a different position that behind the boiler (only a few inches available here as these boilers hide the pipework behind them).

My aim is to get an ECOtech 418 in due course. I assume vastly better system and self protection.

Thanks for the tips