Stuck imersion heater

nofoollikeold

You service an UNVENTED hot water cylinder by (among other things):
1. Visually inspecting it and its connections, checking for leaks, weeps, damage.
2. Removing and cleaning the filter in the combination valve.
3. Checking that the pressure relief valve in the combination valve is working correctly.
4. Checking that the temperature and pressure relief valve in the cylinder itself is working.
5. Making sure that discharge water from the combination or TPR valves runs away cleanly.
6. If fitted, checking the motorised valve to the primary coil is working properly.
7. Checking the immersion heater thermostats where appropriate.
8. Where internal, checking / recharging as necessary the expansion space.
9. Where external, checking and recharging as necessary the expansion vessel.
Its not just a round cylinder full of hot water.  An unvented hot water cylinder has the potential to explode with enough force to knock down the average house.

GDB2222

nofoollikeold said:

Its not just a round cylinder full of hot water.  An unvented hot water cylinder has the potential to explode with enough force to knock down the average house.

That's a possibility, but only if the water inside turns to steam, I presume? 

peter12345678910

There is a valve that makes sure it is  full of water. You can see the water coming out. But it seems to have all plumber detail and cert. in the booklet. 

J_B

nofoollikeold said:

You service an UNVENTED hot water cylinder by (among other things):
...................

Every day's a school day!

nofoollikeold

GDB2222 - yes, if the water turns to steam. 
The water is under pressure, so its boiling point is over 100 degrees.  If a sudden failure occurs, that water will flash to steam at 1,600 times the volume occupied by the water - almost by definition an explosion.  To counter the risk, these cylinders have three levels of protection:
1. A thermostat to shut off the source of heat once the desired temperature is reached.  May be an immersion thermostat or one which controls a motorised valve, or both.
2. A pressure relief valve as part of the combination valve to ensure the cylinder is not over pressurised in normal circumstances.
3. A separate temperature and pressure relief valve which open, as the name suggests, if the pressure or the temperature within the cylinder becomes excessive.
These cylinders cannot be used with "uncontrolled" heat sources, such as solid fuel burners, as it is too difficult to control the input heat.
The annual service is to ensure all these safety systems are working properly.

southcoastrgi

That's not been installed by someone with a G3 cert, I especially like the overflow elbows on the D2 copper, it looks like it was installed by the same idiot that cut through the immersion & cylinder 

peter12345678910

Thanks for the input, just wanted to give the post an end. 

stragglebod

Have I understood this right?

In order to save a £100 plumber call out fee the OP has needlessly wrecked their hot water cylinder, paid nearly a grand for the wrong replacement, installed it incompetently, risked electrocution, and now will need to pay a plumber several hundred pounds more to fix everything?

GDB2222

stragglebod said:

Have I understood this right?

In order to save a £100 plumber call out fee the OP has needlessly wrecked their hot water cylinder, paid nearly a grand for the wrong replacement, installed it incompetently, risked electrocution, and now will need ought to pay a plumber several hundred pounds more to fix everything?

Fixed that for you.