Hot water tank not keeping heat

coffeehound

Thanks, so that was watching the tundish at the same time that the heater made kettle noises?  

These megaflo heaters have an air 'bubble' at the top of the water so that the water can expand.  This bubble needs to be restored every once in a while otherwise it starts dumping hot water overboard and replacing it with cold.  From the manual

The air volume within the Megaflo unit will periodically require recharging to ensure any expanded water is accommodated within the unit. A discharge of water INTERMITTENTLY from the Expansion Relief Valve will indicate the air volume has reduced to a point where it can no longer accommodate the expansion. To recharge the air volume :-

1. i)  Turn off the heat source to the cylinder via programmers/immersion isolation switch(es).

2. ii)  Turn off the water supply to the Megaflo unit by turning off the isolating valve on the Cold Water Combination Valve. Turn the black handle so that it lies at 90o to the direction of flow.

3. iii)  Open the lowest hot tap supplied by the Megaflo.

4. iv)  Hold open the Temperature/Pressure Relief Valve until water ceases to run from the tap and gurgling noise at the valve stops.

5. v)  Close Temperature/Pressure Relief Valve.

6. vi)  Turn on the isolating valve at the Cold Water Combination Valve by turning the black handle so it lies parallel to the direction of flow, when water flows from the hot tap, close tap.

vi) The air volume will be automatically recharged as the unit refills.

Not suggesting that it is this, but perhaps worth checking out, if it were to save getting a tradesperson in.

ForestBluebells

I tried again this morning and couldn’t see any drips. Not sure if it could drip at other times but it isn’t when I turn on the override. Only thing I have not checked is what the temperature is set to but not sure why that would have changed

coffeehound

Ah okay, it was worth ruling that out.  Sounds like it is more likely an electrical fault then as posters have suggested

ForestBluebells

Electrician said I need a plumber?

Section62

ForestBluebells said:

Electrician said I need a plumber?

Did he say what was wrong?

An electrician should be able to check the wiring and (if necessary) change the thermostat.

If the immersion heater had failed that would probably be a job for a plumber, but as you have been getting some hot water it doesn't appear the heating element itself is faulty.

ForestBluebells

He wouldn’t even come out just said it probably needs draining to do anything? Maybe he’s just not got any experience in water tanks? I showed him photos 

coffeehound

Interesting thread here  Similar problem turned out to be due to a faulty mixer cartridge in a tap.  Another member said he'd seen the same fault from a faulty mixer shower

ForestBluebells

Electrician is coming tomorrow morning now after all so will report back what he finds 

ForestBluebells

Ok the cable on the heating element is completely burnt. Electrician said it needs replacement but suggested a plumber to do it as the tank will need draining. Asked a plumber and he said I need a certified plumber trained to work with megaflo so he can’t do it but he’s going to ask around for me

Section62

ForestBluebells said:

Ok the cable on the heating element is completely burnt. Electrician said it needs replacement but suggested a plumber to do it as the tank will need draining. Asked a plumber and he said I need a certified plumber trained to work with megaflo so he can’t do it but he’s going to ask around for me

Have you got a picture of this cable please ForestBluebells?  More out of curiosity and possibly because it might help someone else in the future if we can get a better idea of exactly what the problem is.  If you didn't take one when the electrician was there then perhaps you could ask the plumber to let you take one after they've removed the old element from the Megaflo.

It does also sound like a rather unusual failure (in my experience) so if the element is the original one you may also want to send a picture to customer services at Heatrae Sadia to make them aware of how it failed. If the insulation on the wire has 'burnt' then there is a potential risk of fire or electric shock, so it would be good to make them aware in case this was an latent manufacturing fault and other people might be affected.

If the 'cable' is a fixed part of the immersion heater then the electrician is right about this needing to be changed by a plumber with a "G3" qualification.