Changing immersions on an unvented system....

[cheat007]

Hi all.

Hope someone can answer a question I have. Basically, first floor flat and ive got an unvented system which sole purpose is to heat the hot water for the taps. The system is about 2 years old now and both immersions in the cylinder have failed.

A while back the main immersion packed up and didn't heat the water at all when the system was programmed to come on in the night (economy 7), so to get hot water the second 'boost' or top up immersion heater was used which was fine untill that also packed up.

Now upon looking at the immersions I can see that it appears that they are leaking from around the electrical connections (poor quality immersions i'd suspect) and upon switching the main immersion on via the timer, it makes a hissing noise and produces smoke.

So time to replace the two immersions on the cylinder then.

Now my question is this. Is it any different changing an immersion on an unvented system as apposed to a normal vented system? If I shut off the main feed to the cylinder and then let the water drain out of the cylinder by turning on the hot taps, will I need to worry about the pressure in the system? Is it as straight forward as drain the cylinder down to below the lowest immersion, remove and replace the two 14" immersions and then refill the cylinder with water again?

Hope someone can help

 

[dontknowitall]

Someone who's qualified to work on and install unvented systems can help you - it's against the law (and potentially very dangerous!) to try and do this on your own.

The changing of the heaters is simple enough but setting the system properly afterwards and ensuring it adheres to the regulations is important. The government (sorry - nanny state) has compared this to working on gas.

Sorry to sound negative.

 

[migoplumber]

what you have proposed wont work - as dont know it all states don not touch, you obviously dont understand the principles. get an engineer in.
unvented cylinders can cause huge bangs.

good luck

 

[cheat007]

@ dontknowitall- Thanks for the reply. Had a feeling this was the case, but wanted to double check here first.

@ migoplumber- No I don't fully understand all the ins and outs of the unvented system, hence my asking on here.

 

[Puddle]

When I first took my unvented,there were not that many about but I needed the bit of paper,there are loads of unvented cylinders about now and nice little earners,it should now pay to take the unvented course ,not only for safety but also to get the basics,so you can do the job required

 

[wiltsplumb]

alot of unvented cylinder immersions are not standard sizes and are specific to the cylinder stay clear mate unvented cylinders can go bang big time !! With gas you get a dry explosion with unvented cylinders it is steam! you wouldnt want to be in the way if one goes!!

 

[helpsy]

All parts fitted also have to come from system manufacturer.You can't just fit any old parts.

 

[kirkgas]

@ dontknowitall- Thanks for the reply. Had a feeling this was the case, but wanted to double check here first.

@ migoplumber- No I don't fully understand all the ins and outs of the unvented system, hence my asking on here.

go on to mythbusters and search for unvented explosion, well worth a look

 

[migoplumber]

sorry i didnt mean to offend, just wanted you to get the point. my post still stands - i gave the right advice