Help!! - Advice on hot water cylinder not functioning.

[stevo23777]

Hello

I would be very grateful on some advice on the following issue. We had a vented direct hot water cylinder fitted (with requisite cold feed tank etc) to feed our new Mira pumped digital shower (already have a combi fed, but need to run two showers at once, not enough mains pressure for un-vented). The cylinder is 1800 x 300 (118l capacity) due to space restrictions with a 27" immersion heater, top fed.

When I run the shower, not even at top flow (max 16 l/m), I only get approx 5 mins of hot water. The thermostat on the cylinder was set at 60 degrees, I have increased to 70 degrees but no significant change.

I have put the immersion on all night in case it was a requirement to heat through then top up heat.

If I'm running the shower at 40 degrees and I estimate 2 parts hot to 1 part cold, the equates to only approx 50l of hot water, not even half.

Is this expected with tall thin cylinders? Or should the whole tank heat? My worry is as the tank is so thin that the top third is reaching 60 degrees and flipping the stat.

My plumber doesn't know what is causing this and is suggesting changing the immersion, but my gut is that I may need an indirect (off the combi CH), or a secondary immersion in the base of the cylinder, both of which will require a new tank.

I would really appreciate anyone who has had experience of this and found a solution as I haven't paid for this work yet, and want a working hot water supply before I fully pay.

Regards

Adam

 

[snowhead]

You've got an immersion heater that barely reaches 1/3rd of the way down the cylinder.
That's your problem, you're unlikely to be heating more than the top half to any reasonable temperature.

Fit a second immersion heater in the existing cylinder near the bottom, using one of these;
Immersion Heater Element Mechanical Flange - Stevenson Plumbing & Electical Supplies

You'll need an additional electrical supply if you use both heaters at the same time.

OR
Fit a pump to mix the cylinder contents (de-stratification)

 

[mountainman]

Snowhead is spot on.
It's a bit worrying that your plumber doesn't know what is causing your problem.

 

[stevo23777]

Hi Both

thanks for your replies, plumber is looking at fitting a hot water circulating pump that comes on with the timer for the immersion. Do you think this is a good suggestion? Would it be a low noise level, worries we'll hear it when immersion comes on early in the morning, also will it shift water around fast enough to ensure whole tank is heated? Should I insist that an isolating switch goes on it so re-heat is faster (guessing for one shower the top thirs would be fast and sufficient) rather than whole tank heating.

Once again thanks for your help this has been hugely frustrating and really want a tank full of hot water rather than a third of a tank!!!