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.