Do I need a Megaflow cylinder?

[GSUK]

Hi there,

A had a new Worcester system boiler fitted in the summer to replace an aging gravity fed Servowarm. All works fine apart from the cylinder stat doesn't work properly as (according to the plumber) the 25 year old cylinder is probably too furred up. i.e. piping hot water yet the copper on the cylinder is lukewarm.

He's recommended replacing the cylinder with a megaflow. All very nice but I think it's overkill. I have a typical 1930s 3 bed mid terrace ( plus one bedroom with en-suite in a loft conversion). Both the bathroom and the en-suite have electric showers which I have no intention of replacing.
I've always had enough hot water and the water pressure, although a little low, is fine. I would image that a new copper cyclinder would improve the flowrate anyway if the cylinder is that furred up.

So who's right? Me or the plumber?

Thanks in advance.

 

[warmadmax]

If it aint broke, dont fix it!

if the water is hot, but the cylinder cold,
Then it's retaining heat very well!,
Could well be furred up on the inside,
is the pipe exiting the top of the tank hot to the touch?

if so you could always try changing the cylinder stat for a pipe stat on the top pipe as it exits the tank, wont be as accurate but would solve the scorching hot problem.

Have you got a large cold water cystern / tank in the loft feeding into the bottom of your hot water tank?
if so you've got gravity fed hot water,
as such replacing the tank is unlikely to increase pressue as the pressure comes from the height of the tank above the tap.


If when your electric showers fail in the future, and you want to replace with standard showers, the megaflow would give you balanced mains pressure hot water leaving you free to choose which taps / showers take your fancy.

 

[GSUK]

The boiler had been off for 10 hrs when I came home and tried the water again and it was still very hot so yes it does insulate very well

Is the top pipe the one that vents or does it feed the taps? Just wondering if turning a tap on will increase the temperature of the pipe and thus turn off the boiler prematurely


Yes, it's gravity fed so makes sense re water pressure.

Thanks for the reply.

 

[warmadmax]

The top pipe should be both normally, you should find a tee with the vent going into the loft above the cistern and the tap feed off the other end of the tee.

I'm a diy'er that reads a lot so I might be wrong when it comes to the stats,
And I don't know for sure how the pipe stat would be affected by flowing water but it's more likely to turn the boiler off than the Luke warm cylinder side stat does presently.

Which is the aim, turn the boiler off when the water reaches 65c

Have you got a thermometer handy?
Press its bulb against the cylinder wall and the pipe exiting the top of the cylinder,
If you get a higher reading off the pipe then it should be worthwhile.

 

[xr4x4]

Just replace the hot water cylinder like for like with a vented cylinder.

I'm not sure a pipe stat would work as the pipe would go cold when the hot water ran out, bit late then. Also the boiler wouldn't switch off until the pipe got hot, what if your not running the hot tap. That would take a while.

What you also have to remember is a megaflow uses mains pressure, your system would have to be modified more than you think.

I'm assuming the tank stat is cut into the insulation of the tank?

 

[JonasX]

A three bed mid-terraced? Depending on mains pressure, you should have fitted a good flow rate combi last year. Too late now. You were poorly advised I think.

If replacing the cylinder, consider a stainless steel job, not copper.