Haetrae Sadia / Megaflo Overheating!!

[Diggerless]

Last night I noticed that the hot water was exceedingly hot, at least 20 degrees hotter than normal, so suspect something is wrong with the lower (timer) thermostat? There are two heating elements. The upper one is just an on/off, obviously stays off is using the thermostat-attached one, which is the lower one. The thermostat is set in the permanently-on mode as opposed to using the timer mode (use a lot of hot water so makes sense to just leave it on.

From memory the setting for the element itself (sorry, don't know the technical term) has four settings. I am fairly certain it is set at the second or third setting. I am guessing this is where the failure, or problem lies.

I turned the isolation switch off overnight for this timer and connected element unit.

I have switched it back on this morning. Presumably if it continues to "overheat" then I should see water dripping from the Pressure Release Valve?

Haetrae Sadia / Megaflo are closed obviously.

I will switch to the upper heating element if this persists but does anyone have any suggestions otherwise?

 

[Agile]

It will not drip unless the temperature reaches 95 C.

Sounds like a failing thermostat. For the time being you could try turning the stat down to the minimum.

Any work on an unvented cylinder like this should be done by someone with the G3 qualification.

Tony

 

[Diggerless]

Thanks Tony.

If I turn down the thermostat to the minimum and it still overheats is it safe to leave on or should I switch to the upper always-on element?

 

[Agile]

If it still overheats then I would switch it on but only for a very limited time so that it reheats the water but only to the required temp.

Normally the lower element is on an off peak tariff which is much cheaper! But you seem to have been using it on peak !

Tony

 

[Diggerless]

Thanks Tony. I have turned down to the minimum.

Interestingly I left it switched on for the last hour and when I turned on a hot tap there was no mild release of pressure. There is always a slight "spurt"when the hot water has been run down and Megaflo is reheating. Leads me to believe the thermostat has or is failing too!

As you suggest I may have been overusing the lower thermostat!!

 

[Diggerless]

Out of interest are the thermostat and heating element an all in one sealed unit necessitating draining down the Megaflo or can the thermostat be replaced separately?

 

[HERTS P&D]

The element would need the tank to be drained down to change but you don't need to drain down to replace the thermostat.

Andy

 

[Diggerless]

Just spotted that the Safety on the stat itself had cut in. So now Reset with the stat on the lower setting. Will keep an eye on the temps and switch off if it continues to overheat.

Thanks for your input chaps.

 

[matt1e]

Just spotted that the Safety on the stat itself had cut in. So now Reset with the stat on the lower setting. Will keep an eye on the temps and switch off if it continues to overheat.

Thanks for your input chaps.

you'd be better off swapping over the stats for the time being, as presumably the upper stat is ok

Matt

 

[Diggerless]

Just spotted that the Safety on the stat itself had cut in. So now Reset with the stat on the lower setting. Will keep an eye on the temps and switch off if it continues to overheat.

Thanks for your input chaps.

you'd be better off swapping over the stats for the time being, as presumably the upper stat is ok

Matt

Good idea. Guess that is a relatively simple job, once power supply has been isolated of course?

 

[Agile]

There is no firm evidence the stat is faulty. It may have just been set too high and tripping the resettable safety stat.

Tony

 

[matt1e]

There is no firm evidence the stat is faulty. It may have just been set too high and tripping the resettable safety stat.

Tony

Last night I noticed that the hot water was exceedingly hot, at least 20 degrees hotter than normal

who do you think has turned it up then Tony?

yes its an easy job to swap out

 

[DP]

There is no firm evidence the stat is faulty. It may have just been set too high and tripping the resettable safety stat.

Tony under what condition will the O/H trip to what is a 'working' temperature

 

[Agile]

I dont know if thats how they are supplied, but I have encountered quite a few in nearly new installations where they will trip if the temp adjust is turned to maximum.

Thats not helped by many owners who think that hot water should be at a higher temperature than the recommended 60 C and turn it up.

Tony