Megaflo problems

[Mike2007]

The 250ltr cylinder I have isn't supplying hot water. It's supplies luke warm water or intermittent hottish water. It has been drained down and recharged. Plenty of hot feed from the boiler primaries. There is red hot water from thermo pressure release valve near the top of the tank but virtually nothing from the dhw draw off.
I am confused as it gets??

 

[TCCHeating]

If the water in the cylinder is hot then somewhere the hot is being mixed with cold before it gets to the tap. Could be a passing mixer such as a shower. Also do you have a blending valve anywhere?

 

[Mike2007]

If the water in the cylinder is hot then somewhere the hot is being mixed with cold before it gets to the tap. Could be a passing mixer such as a shower. Also do you have a blending valve anywhere?

No there isn't a blending valve and mixer showers are miles away. It's like magic trick, I can't see how the discharge in the tundish can be very hot but tepid at the drawoff point. Could a failed baffle produce such wierd results??

 

[TCCHeating]

I'm still punting on a passing mixer somewhere. Can you isolate the hot water without isolating the balanced cold? If you can then turn on a hot tap and see if you still get water

 

[Mike2007]

Well I am willing to try anything at the moment

 

[Mike2007]

I'm still punting on a passing mixer somewhere. Can you isolate the hot water without isolating the balanced cold? If you can then turn on a hot tap and see if you still get water

I can isolate both. Mind you its not balanced, there is a separate prv on the cold. But I guess you are suggesting high pressure cold is forcing its way across a mixer point in system?

 

[TCCHeating]

Yes. Isolate hot water only. Then open a hot tap. If the water continues to run then something is passing the cold into the hot. Showers are the main culprit. But it can be any mixer device

 

[Gas2Air]

If the water in the cylinder is hot then somewhere the hot is being mixed with cold before it gets to the tap. Could be a passing mixer such as a shower. Also do you have a blending valve anywhere?

No there isn't a blending valve and mixer showers are miles away. It's like magic trick, I can't see how the discharge in the tundish can be very hot but tepid at the drawoff point. Could a failed baffle produce such wierd results??

I'd be looking at why you have water appearing at the tundish first.

 

[Mike2007]

If the water in the cylinder is hot then somewhere the hot is being mixed with cold before it gets to the tap. Could be a passing mixer such as a shower. Also do you have a blending valve anywhere?

No there isn't a blending valve and mixer showers are miles away. It's like magic trick, I can't see how the discharge in the tundish can be very hot but tepid at the drawoff point. Could a failed baffle produce such wierd results??

I'd be looking at why you have water appearing at the tundish first.

Because I opened it to see if it was hot at this point

 

[dilalio]

Blockage at top of cylinder in HW draw off ?

 

[dilalio]

Also, have you checked air charge at potable vessel?

 

[TCCHeating]

Also, have you checked air charge at potable vessel?

On a megaflo?

 

[dilalio]

Oh, Oops! Teach me to read threads properly eh!

 

[simond]

The floating baffle does nothing, so if it fails, nothing will happen.

A Megaflo, like other unvented cylinders, is just a tin full of water. Cold water is applied at mains pressure at the bottom, and this displaces the heated water out of the top, when you open a tap.

Heatrae Sadia marketing would like you to believe there's more, but there isn't. The floating baffle was intended to separate the air from the water, but this doesn't work, a fact now acknowledged by Megaflo on a large label on the side of the cylinder.

You've opened the T&P valve (never a good idea) and hot water comes out. There isn't a way anything but water of the same temperature can be produced at the top of the cylinder.

So, although I am the last person to advocate a Megaflo, there's nothing wrong with yours. The water is being mixed further down the line with cold, as everyone has told you.

 

[dilalio]

As TCC said, if you can, isolate hot near to cylinder, open a hot tap (at high point - means you won't have to wait for pipes to drain) if you get constant flow then it's crossing at ANY mixer on the system!
Then, if you can, isolate cold or hot or both to each mixer, one by one, until your hot is back to temp on another draw off and you will have found the culprit mixer... If very unlucky might be more than one.
Replacement inlet cartridges and thermos are not cheap for almost all mixers - you could try removing the culprit one and cleaning/descaling it - removing any o rings first.
Also, if you can, fit a balancing valve to the system, to equalise the hot and cold.