Immersion heater - causing overflow problem?

[plodder]

I am on economy 7 electricity. I accidentally left the immersion heater (day switch) ON for a day recently.

Now I notice that there is a constant drip from the overflow pipe which juts out of the outside wall and feeds a downspout.

I also notice that when the mains water stopcock (this feeds the cylinder) is OFF the drip stops.

I also notice that when the mains water stopcock (this feeds the cylinder) is ON the drip starts again.

When the water is ON, the cylinder also constantly hisses/fizzes quietly - Has the heating element gone?

Would this be a reason for the overflow drip on the outside wall?

I have done some plumbing but never tangled with immersion heaters - and I can't see the connection between the two events. Is an overflow at the base of the cylinder linked to the outside wall overflow?

any advice is very welcome.

thanks

p.s. the cylinder is model: "TRIBUNE" UNVENTED WITH "VAREM " EXPANSION VESSEL.

THE GUAGE BETWEEN THE CYLINDER AND EXPANSION VESSEL IS SHOWING 2 BAR, WHICH I BELIEVE IS WITHIN RANGE.

 

[Bahco]

These systems need attention by a plumber with a unvented ticket.
Make sure whoever you call is qualified as in the wrong hands can be very dangerous

 

[plodder]

Thanks.

I have been doing some more testing.

I checked the tundish at the immersion drain exit for signs of water and it showed that the dripping was definitely coming from the immersion outlet which is connected to the pressure relief valve/ temp relief valve (these two valves both feed the drain). this proved that the valves were letting out water because the system pressure/temp was too high. Because I had left the "day" element on. However surely the day element should have cut out with the thermostat once it reached he setting of 50 degrees?
Could it be the thermostat is not functioning. whats the lifespan of elements and thermostats typically?

To stop the drips and stabilise the system - I turned the cold stopcock off . I then drained the hot water off in the kitchen sink and then left the cold off and the immersion unfilled for about 24 hours. the dripping stopped. I then turned cold on again and the immersion filled. using the regular night element the system is working fine - no dripping at all.

Also using the day element for about 30 mins the system is working fine.

what concerns me is why it started dripping in the first place. why should the system overheat or go above the relief pressure setting if the day element thermostat is functioning correctly? or is this just normal? would any normal system begin to drip through the relief valve if the day element were left on for 24 hours regardless of the thermostat?

 

[corgigazza]

expansion vessel may have lost its internal charge to check this:

turn of water supply to cylinder and relieve water pressure (open tap). Remove dustcap from ex vessel valve. Check what the pressure should be on side of vessel (1.5-3 bar) if incorrect re pressurize using foot pump to correct charge leaving tap open if the vessel will not charge it may be due to the internal rubber bag split meaning a new vessel is required of correct volume

 

[plodder]

I've had the immersion heater refurbished. ive changed both the elements and the expansion relief valve (4 bar) and the temp/pressure valve (3.5 bar) . i also charged the vessel to 30psi/2.1bar as required. the vessel; it appears to be holding its charge ok. now I find the overflow is dripping water again. it doesnt make any sense. what else can be causing this?

 

[kevplumb]

I've had the immersion heater refurbished. ive changed both the elements and the expansion relief valve (4 bar) and the temp/pressure valve (3.5 bar) . i also charged the vessel to 30psi/2.1bar as required. the vessel; it appears to be holding its charge ok. now I find the overflow is dripping water again. it doesnt make any sense. what else can be causing this?

i hope you've got a g3 ticket

 

[raykeeley]

most people don't realise oe under stand that, unvented systems over 15ltr need to be installed by someone who hold the unvented ticket. this includes servicing and maintaining. unvented systems need to be serviced every year. if any of the safety devices are running, then this is telling you to sort it or else. this include the pressure relief valve temp pressure relief valve and the thermal cut out. if they fail or if they are left THEN YOU HAVE A TICKING BOMB IN YOUR HOUSE . call a plumber with a ticket now.

 

[ChrisR]

Do you know what your mains water pressure is? Could be pressure reducing valve letting by? Call your Water Provider, they'll be able to tell you from your postcode.

 

[plodder]

thanks for the replies.

the mains water pressure is 4 bar. I tested it myself with a pressure gauge on the supply to the washig machine.

I DID have a plumber with an unvented ticket install the various valves and elements. it was working fine for the first couple of days. it doesnt drip when the system is unheated. only when the elements have been on for an hour do I get any signs on water dripping out. ive tried flushing the relief valves with the levers, as advised by the suppliers, in case there is any dirt under the valve seating but it hasnt really helped.

could be the pressure reducing valve is letting by . even so the two saftey valves are set at 3.5 and 4 bar - so the pressure reducing valves would have to be letting by a lot to blow those valves.

 

[raykeeley]

are you shore the pressure vessel is holding its charge. the way to check is switch of the electric, then the water. reduce the pressure then put a tyre pressue uge on this will tell you what is reading. just to make sure.

 

[keego]

Interesting this one, we regulary work on unvented systems changing T&P valves & RWC kits even though we have no experience on these systems. Do I need to have this G3 ticket to do this work & do all these systems need annual checks, as from what I can gather the systems we work on have never been checked since they were installed in the 80's.

 

[raykeeley]

not being funny, but this was all new to me when i got sent on the unvented course. its illegal to install a system over 15ltr unless you have done the course. also you are supposed to inform the local authority of what you are doing ten days before you carry out the work, unless you are self certified.

 

[keego]

not being funny, but this was all new to me when i got sent on the unvented course. its illegal to install a system over 15ltr unless you have done the course. also you are supposed to inform the local authority of what you are doing ten days before you carry out the work, unless you are self certified.

Yes but what about fitting like for like on unvented???

 

[keego]

& does this include boiler swaps?

 

[raykeeley]

i doesn't matter, any work carried out on the appliance ie renewing altering replacing, you need to inform the as per the regs. a good guide is the wras guide book. all in there, and its got colour pictures.