Hot water seems to be travelling from cylinder but no taps turned on

[Mike_Iver]

Hi

A while ago we replaced a Megaflo for an Ecocent hot water cylinder. Unvented

Due to the size of the new cylinder we had to relocate it slightly. But otherwise we used all the same fittings as previously

The hot water outlet from the cylinder is HOT. I mean the heat travels metres along the pipe. We fitted a valve about 1 metre from the cylinder, and when that's turned off, the heat stops at the valve. This implies to me that water is actually flowing slowly along the pipe. Yet no taps are turned on. We do not appear to have a leak anywhere. So I am stumped

Additional info. We have the Megaflo 3 bar pressure reducing valve fitted, which feeds the cold supply to the cylinder - could this be faulty? The cylinder feeds a double shower in a changing room. Of these two, one works fine, but the other only ever sends out lukewarm water - could the thermostat in this shower be faulty and it is allowing the hot to flow through to the cold supply? The cylinder also feeds another shower which works fine, and 2 sinks, which also work fine

I'm no plumber myself. But handy man installed this cylinder and another of the same upstairs. The upstairs unit works perfectly

 

[nortonj]

Handy man? Was he g3 registered?

 

[muggles]

As above, the words "handy man" are rather worrying. Unvented cylinders are a controlled service that should only be installed by trained, competent, G3-registered installers. The installation should then be registered with Building Control. Incorrectly installed unvented cylinders can explode with enough force to demolish your house.

With that out the way, let's get to your problem... first off, I'm concerned that the original Megaflo valve remains in place. This should have been replaced with the control set supplied with the new cylinder. Unlikely to be causing your problem, but certainly something to be addressed, along with any re-used safety valves that should have been changed for new ones

Your showers may be the problem - is the cold fed from the mains, or a loft tank?

 

[Mike_Iver]

Thanks

First off, I may not be an expert, but I am not an idiot either (arguably). I have had the installs looked at by 2 G3 qualified plumbers, both of which were happy with it, one did express concern about reusing the 3 bar reducer (which is fair enough). Neither plumber discovered the terrible terrible error we had made with the 25kw ASHP, when neither my handy man or me knew what we were doing. I have seen an unvented cylinder explode on YouTube and it scared the **** out of me.

You can read all about the 3 installs here, and see pics
https://installingandlivingwithashp.wordpress.com/
Happy to hear criticism!

To answer your questions:
The Ecocent came with a P&T valve installed, which we obviously used - I wouldn't have installed any used safety devices. We only re-used the 3 bar reducer, as the new cylinder did not come with this.

The two showers I mentioned are right next to each other in the same room. One works fine, the other does not. I do not have any tanks in the house. All water is mains pressure - but has been through said 3 bar reducer

The mains comes in, in the basement, goes through the 3 bar reducer, and is fed to the basement Ecocent. The hot output Tees off. One way to the two showers, and the other way to 3 sinks and an upstairs shower. The best thing for me to do would be to fit stop valves on the 2 Tee outputs, as that would prove whether the problematic shower is causing the hot water to travel along the pipe

 

[bernardgreen]

the heat stops at the valve. This implies to me that water is actually flowing slowly along the pipe.

If there is a length of vertical pipe on the hot water then this may be applicable.

It goes against "normality" that water can flow in two directions in the same pipe but in the lab with glass pipes it can be clearly seen.

 

[Mike_Iver]

Wow really?

The hot comes out of the cylinder HORIZONTALLY. Then there are a number of 90 degree fittings, and then a 45 degree upward and sideways movement, then horizontally to the Tee piece. Then both of the Tee'ed pieces go vertical. The pipe is only hot for the first 3-4 metres (where the pipe is all horizontal) from the cylinder

 

[bernardgreen]

Convection flow can also occur in a horizontal pipe. Hot water at the top of the pipe from the tank and cooler water at the bottom flowing back to the tank.

The effect is small, very small if the pipe is adequately lagged.

 

[Mike_Iver]

This pipe is HOT. If it were merely warm I wouldn't be concerned. I have yet to lag it, purely because I want to fix the issue and know it's fixed, then I'll lag it. I don't think it's convection - although as previously stated I'm no expert