megaflow elements not heating up, despite element and stat testing fine

[cairns]

Hiya, got an old heatrae sadia megaflo which looks over 10 years old. Just got this flat as its been empty for a while. Turned it on but no joy no hot water, there are 2 elements, one normal and 1 boost, tested the supply to both of the two radials supplying the elements and have 240v, have got 240 at both stats on the supply side. Have also checked continuity to the supply side of each stat from the fusebard all good. The stat on the outgoing side is working was getting 240v on both elements. Then thought it must be the element, so disconnect both from the stat and tested for continuity, was getting like 18ohms which i gather is right. I also used a clamp detector on the load side of the stat going to the element and was getting 12amps which i also think is about right.

Its giving me a headache, dont have alot of experience in heating problems soo would appreciate any help. thanks

 

[Plonker 3]

Is there water in the tank?

 

[HandySparks]

Hiya, got an old heatrae sadia megaflo which looks over 10 years old. Just got this flat as its been empty for a while. Turned it on but no joy no hot water, there are 2 elements, one normal and 1 boost, tested the supply to both of the two radials supplying the elements and have 240v, have got 240 at both stats on the supply side. Have also checked continuity to the supply side of each stat from the fusebard all good. The stat on the outgoing side is working was getting 240v on both elements. Then thought it must be the element, so disconnect both from the stat and tested for continuity, was getting like 18ohms which i gather is right. I also used a clamp detector on the load side of the stat going to the element and was getting 12amps which i also think is about right.

Its giving me a headache, dont have alot of experience in heating problems soo would appreciate any help. thanks

That 12 amps you measured is giving you nearly 3kW power dissipation somewhere; presumably in the elements. So how long are you leaving it to heat up and are you confirming the current remains at 12A for a good length of time?

And how do you know that it's not heating up? Is it by feeling the top of the cylinder, or is it by drawing off some water?

 

[Sintra]

Sounds like your immersion is working ok if it's drawing 12A. Have you checked that the water supply is on, the strainers are clear and the cold water combination valve is fitted correctly and open.

 

[cairns]

Thanks for the replies, yes tank is filled, water main is on. Am testing it by feeling the hot water pipe at the top. Have turned the hot tap on but just cold water has come out, left on for about 25mins, but no feeling of warmth in the top pipe nor any noise can I hear as I have heard from immersions before :s

 

[PEG]

Are both elements drawing current and not producing any heat? 12 Amps is doing something,somewhere...

 

[poolsharkuk]

Limescale build up on the imersions could be the cause if the megaflow hasn't been used for a while. Is there an
inhibitor on the cold flow? As mentioned its drawing is full current so for what it's worth change the elements. At the same time install a inline scale inhibitor. If there is limescale on the elements and there is also a scale inhibitor. Change the inhibitor too.

 

[UNG]

What size is the cylinder and how long are you leaving it turned on for the water to get hot

I assume the stats are set at a temperature that will allow the water to get hot!

 

[cairns]

Yes stats are set to 60 degrees. Leaving it on for 25mins, it's fairly large. Not the biggest but not the smallest.

 

[Darkwood]

Have you load tested both elements and have you done it periodically ...a faulty stat maybe cutting power after you have initially powered up and measured.... is the flat large .... dont forget you will have to draw all the water held in the pipes out before you will start seeing the contents of the tank getting through.

Is the tank insulated - if its cold it may take a lot longer to heat up if its just radiating into the surrounding air.

If the flat has been empty for a while is their any chance you may have ice in the tank ..not enough to block flow but enough to take a lot longer to heat up.

 

[telectrix]

furred up elements seems the favourite. preventing heat transfer into the water.

 

[UNG]

Yes stats are set to 60 degrees. Leaving it on for 25mins, it's fairly large. Not the biggest but not the smallest.

Would you care to be a little more objective on the size some of these things can take up to 3 or 4 hours to heat up to temperature

 

[cairns]

Would you care to be a little more objective on the size some of these things can take up to 3 or 4 hours to heat up to temperature

Its 145litres, will checked to see if the stat was still working after 20 mins and was still live. Anyone know if in the old heatrae sadia megaflows of a normal element will fit or does it have to be a special one. Yeah cheers know it has to be drained down or I would get very wet.

 

[Engineer54]

Some of those thermostats can be real pains to set correctly. Not the most accurate of devices at the best of times. The setting wheel on many can be well out of sync with the outer temp setting values!!

 

[snowhead]

Anyone know if in the old heatrae sadia megaflows of a normal element will fit or does it have to be a special one.

If it's the push fit stat, it's a Megaflow element that you need the key to remove the retaining ring;

Top and bottom elements are different.

Megaflo Immersion Heater | eBay

 

[UNG]

Its 145litres, will checked to see if the stat was still working after 20 mins and was still live. Anyone know if in the old heatrae sadia megaflows of a normal element will fit or does it have to be a special one. Yeah cheers know it has to be drained down or I would get very wet.

So at 3Kw it will take 158 mins to heat up at 6 Kw it will take 79 mins to heat up

The elements in these cylinders are normally a special shaped incoloy element