Possible Limescale on immersion

[MickBrown]

I look after the plumbing at a small hotel with a busy restaurant that runs from early morning till late at night 7 days a week. The hot water for the kitchen is a direct heated megaflow, recently the hot water was running out quickly so checked the megaflow immersion heaters. For some reason the top immersion has had the thermostat removed and the wiring disconnected, don't know why as was before my time and nobody there knows. The bottom immersion was working but the thermostat was cutting in and out quite quickly, I do not have an unvented ticket so all I could do was change the thermostat, however before I changed it it burnt out completely and no hot water. I changed the thermostat last Thursday but it was still cutting in and out quite quickly but not as quick as before, on Friday they said the water was only luke warm. This could have been because the immersion hadn't had time to heat the water completely but will check today. If there is still a problem could it be caused by limescale flakes building up in the bottom of the tank and stopping the water flowing around the immersion properly? I work with a colleague who has an unvented ticket so I can deal with the problem under his supervision, he didn't seem to know why the thermostat was recycling quite quickly but I have not mentioned scale problems to him yet.

 

[chris watkins]

It is going to be scale Mick, When was it lasted serviced ??
I should warn you, as far as I am aware there is no provision under Part G of the Building Reg's for you to work on a hot water system without having the ticket (& that includes changing thermostats) whether that is having a colleague who does have one or not. He should be carrying out the work (unless you are a trainee working along side them).
We look after restaurants that have to be descaled twice a year.

 

[MickBrown]

Thanks Chris, What I actually meant was that he would be there doing the job and I would be doing the donkey work. I want to do the course sometime but believe that the course does not do any practical work so any opportunity to help as his 'Trainee' is worthwhile. Didn't know I couldn't even touch the thermostat so learnt something there. Would you remove the scale manually through the thermostat hole or are there chemical solutions?

 

[chris watkins]

The thermostats contain both the control & overheat stats so important you understand how they work & what job they do (practical training is good but do the course then both combine) One I know went BANG because an sparky wired out the overheat stat (there were a few other things wrong but he was the one that got done.
I would not use chemicals myself, to dangerous & hard work, we use a low tech but highly effective method, albeit key hole surgery.
Regarding the upper immersion wiring, would suggest you check loadings on the power supply unless you have to separate supply to each as normally one immersion one supply the upper one is used & a booster or stand-by unless hot water requirements are high.
Have fun.

 

[MickBrown]

Thanks again Chris, the stat is all in one so only a live and neutral. The top immersion has it's own supply but the stat has been removed, the wires taped up and the fuse removed. None of the staff there today knew anything about it, the owner is in tomorrow so he may be able to shed a light on it. It would be better for them to have both working so if one fails, as did the working one last week, they will still have hot water. They are closed for a week in January so an ideal time to descale the hot water tank although as the thermostat is constantly switching off and on it may burn out again. I have warned them of this but they hope it will last until Jan.