Hi all

I was on here some weeks back , as we were having hot water shortage
issues.

I should point out that with the OLD thermostat (with no *safety* cut
out) and with the immersion heater timer buggered and set to permenatly
on, thus operating on the thermostat only, we never had any hot water
problems....ever.

After fixing the immersion heater timer so it actually worked rather
than being on all the time.

The water just didn't seem to be hot enough for 2 showers (of no more
than 10 mins each).

I've replaced the hot water tank (1200mm tall x 450mm diameter) and
have also fitted a 36" immersion heater with 18" thermostat. I'd
initially fitted a 27" immersion, but discovered the old tank had a 36"
in it, so I thought I'd put a 36" in the new tank too.

Thankfully, the new tank had the water connections in the same places
as the old one, so the hot water to the taps (with the vent up to the
cold water tank in the loft) comes off the very top of the cylinder,
with the shower hot water take off coming off the side of the cylinder
about 20 to 30cm lower than this. So none of the pipework has been
altered at all.

The shower is supplied by a pump, with a cold water feed to the pump
from the tank in the loft and the hot water feed from the hot water
cylinder on the landing (ie: same 2nd floor that the bathroom is on).
The pump settings haven't been changed and it's still on it's lowest
boost setting (no idea what this is though).

The new thermostat doesn't have temperatures marked on it, simply + and
-. If I have it set to maximum, it seems to trip out, so I have it
slightly below (literally a tiny bit lower) and it seems ok.

The problem with not enough hot water is still the same though - the
shower (a thermostatic controlled mixer valve type) starts running
colder and colder after about 15 mins.

Now, the shower hot water pump supply pipe off the cylinder is hot
before the shower is used, but when the shower has gone cold, this pump
supply pipe is also cold.

There is still scalding hot water coming out of the taps.

I'm really confused, as the immersion heater is set to come on for a
good 5 hrs before we use the shower in the mornings - and being a
bloody huge immersion, it reaches almost to the bottom of the cylinder,
so should be heating a lot of water....right?

The only thing I can imagine is that the new thermostats (I've tried
2...the first one was really crap and kept tripping all the time)
simply don't heat the water enough, or the hot water at the top of the
tank is cutting out the heater, so the majority of the tank is still
not being heated?

Do the thermostats measure the water temperature from the tip (ie: the
bit deepest into the cylinder) or the entire length of the thermostat?


I was going to try one of those external tank thermostats and mount it
further down the tank, I've seen a 16amp one on the Screwfix website
which I think woudl do the job.

Any thoughts / advice would be greatly appreciated.

On 7 Feb 2006 01:24:04 -0800, "Russ"
wrote:

Any thoughts / advice would be greatly appreciated.

Hi,

How hot is the water from the cylinder? (eg at the tap)

Also what's the shower flow rate in litres per min? (eg into a bucket,
weigh bucket on bathroom scales)

I wonder if there's any good reason why the shower feed can't be taken
from the top of the tank...?

cheers,
Pete.

I don't know to be honest.

Just seems odd that the pipework hasn't been altered, and it used to be
fine before new timer & thermostat

Russ wrote:

The only thing I can imagine is that the new thermostats (I've tried
2...the first one was really crap and kept tripping all the time)
simply don't heat the water enough, or the hot water at the top of the
tank is cutting out the heater, so the majority of the tank is still
not being heated?


Any thoughts / advice would be greatly appreciated.

It does sound as if there is a spectrum of temperatures from the base
of the tank
to the top of it.

Whilst not a solution to your problems, how about investing in (say) a
digital
thermometer and measure the temperatures every ten minutes at different
heights
of the hot water tank?
This might give a clue to where the problem lies.

HTH

Mungo

On 7 Feb 2006 03:07:05 -0800, "Russ"
wrote:

I don't know to be honest.

Might be worth spending a few £ on a thermometer and finding out, eg a
cooking thermometer will do. Whether the water temp is 50C, 60C, or
80C, each leads to a different course of action.

Just seems odd that the pipework hasn't been altered, and it used to be
fine before new timer & thermostat

Better to work out whether your new setup is going to give you what
you want.

Anyway why the need to heat a whole cylinder with electricity, what's
wrong with a gravity fed dribble...? Seriously though, it would be
better heated by a gas boiler.

cheers,
Pete.