Megaflo - hot water outlet pipe always hot?

[ndoubt]

Friends - quick q on the Megaflo unvented indirect cylinder - ive been trying to get to the bottom of why my tank isnt holding its heat overnight when no hot water taps are on.. i use evohome hot water kit to set the temp at 55 overnight , by morning its 35 degrees. Suggests to me that hot water is being drawn somewhere in my system - something that seems to be supported by the fact the outlet pipe at the top is always hot (or should this be the case) - and that its gradually taking cold water from the mains. I had the air gap recharged, nothing coming out the tundish etc. Any ideas?
Should that pipe out the top be permanently hot? or should it only be hot when hot water is being drawn?

 

[ianmcd]

yep sounds like you have a leak somewhere or a dripping tap or shower

 

[Madrab]

Overnight, turn off the cold feed to the cylinder and see if it stays the same temp till the next day.

 

[jjimjam]

About a year ago I noticed that a cold water tap in my house sometimes ran hot. It took me a few weeks to work out that a check valve on my megaflo was on backwards. It didn't hold temperature well. Also the tank would empty when turning off stopcock and opening a cold tap. It had been like that for years and years, and I had lived in the house for about 2 years! Probably not your problem, but something to consider.

 

[jjimjam]

sorry, not backwards. In wrong place.

 

[ndoubt]

yep sounds like you have a leak somewhere or a dripping tap or shower

theres nothing obvious... i read somewhere about water 'passing' in shower/tap mixers ... not sure i fully understand it but could be an issue?
if we had a leak, given this has been plumbed this way for years, think we'd have found it by now//

 

[ndoubt]

Overnight, turn off the cold feed to the cylinder and see if it stays the same temp till the next day.

so heta the tank, then turn off the cold feed? this is to distinguish if the problem is cylinder related or flow/leak related right?

 

[ndoubt]

About a year ago I noticed that a cold water tap in my house sometimes ran hot. It took me a few weeks to work out that a check valve on my megaflo was on backwards. It didn't hold temperature well. Also the tank would empty when turning off stopcock and opening a cold tap. It had been like that for years and years, and I had lived in the house for about 2 years! Probably not your problem, but something to consider.

hmm ok - have had a plumber round to service the megaflo so would have thought something like that may have shown up?

 

[ianmcd]

hmm ok - have had a plumber round to service the megaflo so would have thought something like that may have shown up?

not really unless you spicifically mentioned this

 

[Madrab]

so heta the tank, then turn off the cold feed? this is to distinguish if the problem is cylinder related or flow/leak related right?

It's a quick and easy way to check. Once up to temp and you turn off the cold feed then if the temp stays stable then you know there's a leak in the HW system somewhere. If it still drops then you are looking elsewhere.

 

[ndoubt]

Righto i’ll do it tonight and report back! Thanks all..

 

[ndoubt]

It's a quick and easy way to check. Once up to temp and you turn off the cold feed then if the temp stays stable then you know there's a leak in the HW system somewhere. If it still drops then you are looking elsewhere.

The temp still dropped! 55 to 32 overnight..

Suggests my cylinder isn’t working properly? Tho surely even if it wasnt you’d expect water to keep a lot more heat? Or the evohome hot water kit hasn’t been installed correctly and measurements are off?

What should the next steps be do you think?

 

[polesapart]

Sounds like you're losing heat via the cylinder coil, possibly through gravity circulation.

At a guess DHW zone valve permanently open - seized or wrongly wired.

I'd start with feeling the primary pipework for warmth half an hour after switching off rads and hot water.

 

[ndoubt]

So as the coil cools it cools the water .. or something else like a fault? any thoughts ?

 

[Madrab]

OK, so next task would certainly be to check the hot water kit. Though presuming that was ok was a given, as really that would be the first thing to check but no matter. Your cylinder certainly shouldn't be dropping 23deg over 8 odd hours. I'd run is heat up the HW, then temp test at an outlet, then do the same in the morn.

The only way the coil would draw heat out of the cylinder to any real degree I would think is if cold water was being circulated through it.