water not staying hot with an immersion

Discussion in 'Plumbers' Talk' started by dave200, Mar 26, 2014.

  1. dave200

    dave200 New Member

    Thanks for all your replies at least it gives you something to think about. All I can say for definate is that old immersion I had on a timer and was only on for half an hour this alos has a neon light which comes on when timer is on. I had checked and it was only half an hour for the day. When I fitted the new immersion I did not change the timer in any way (well not until I was not getting enough water so increased the time). The tank is around 45 inches tall by 18 " diamter and immersion heater is 27" so I appreciate only the 27" or so will get heated or there abouts. The boiler heating coil comes out bottom of tank so again I can appreciate that when heated by boiler it would heat the whole of the tank where as immersion only about 3/4. So straight away by using immersion I am going to have less water, but this does not explain how old immersion kept hot water. I am am guessing the old immersion was the original as I bought house when it was around 10 years old so I swopped it likefor like. The engineer when he cam replaced the main controller in the kitchen and just the motorised head of the three way valve(not the valve itself) and nothing else according to him. I think the problem may be that everything at present is working ok but the fault was before. This gave me hot water for a long time whihc I got used to. My options may be to buy a longer immersion? or conceed to the fact that I simply will not have enpugh water by just using the immersion. I still cannot think why after the engineers visit things went wrong. I had been using the old immersion for around two months or so prior to his visit and it all went wrong after that.
     
  2. Hi Dave.

    There are quite a few other variables here too that could have affected the original immersion effect.

    For instance, if you heat a hot cylinder and don't touch it, the hot water will stay floating on the cold layer for longer. Once you run a tap - or do you even have a power-shower with a pump that 'pulls' hot water out of the tank? - then there will be a little more 'mixing' of the hot and cold in the cylinder as cold water flows in at t'bottom and 'agitates'.

    So, did your morning or day behaviour change? Taking showers at different times? Did you have visitors staying?

    Whatever is the cause of the 'super-immersion' you had before, you will know that you don't get something for nothing. If it takes a 3kW immersion an hour to heat a whole cylinder of water to 60oC (and I haven't a clue what the figures actually are...) then that is what it takes. Your old immersion - which was certainly no bigger than 3kW (unless it was twin-element wired up incorrectly...) - just could not have given you the same results in half the time. Couldn't have.

    Whatever it was that gave you the 'whole-day hot water', you were paying for it in your bills - somewhere, even then.

    And this is where the problem lies with me - the wonderful situation you described as having before the boiler was fixed just couldn't have occurred, imo. Something is amiss - eg: the element was on for longer than you thought (really - you watched it click 'on', and also saw it when it went 'off'? Or. it was put on again by someone in the house for a 'top-up' (perhaps they didn't want to tell you... I did this in 'digs' when a student - over-rode the LL's timer when needed...).

    Or something.

    But - a whole day's scalding hot water from a half-hour immersion? I just can't see it.
     
  3. dave200

    dave200 New Member

    I agree it does seem good but that is what happened. When I put the boiler on to heat the water this also is on for only half an hour a day and this heats it up fine. ( I don,t know if an immersion or boiler heats water quicker). But anyway I don,t think I am going to get that ideal hot water back. For people that use just electric though for heating and hot water. If I was too put the immersion on for say hour and a half in morning ( to catch last of economy seven) how long would you expect it to last. For me say by six oclock that night no hot water left and this is so even if out at work all day so no hot water used at all? but using boiler water lasts much longer
     
  4. I don't know the answer, sorry Dave. But, that does sounds not right - if no (or little) hot water is drawn during the day, the tank should be capable of storing the hot water until required in the eve.

    Two ways it generally loses heat - one is through simple heat loss through the tank insulation, and the other is through water convection out the top pipe.

    My understanding is that the pipe coming out the very top of the tank (which supplies the hot water and also goes to the 'overflow' - what's it called, the safety bit) should 'elbow' shortly after exiting the tank.

    Otherwise hot water will rise up that pipe, cool and return back down in a circulatory motion.

    But, I doubt that's the problem...
     
  5. Phil the Paver

    Phil the Paver Screwfix Select

    You say you only heated for 1/2 hour on old immersion, what times were that 1/2 hour, bearing in mind you said is was on economy 7.
     
  6. sam spade

    sam spade Active Member

    What are the on/off times for the Immersion?

    What are the on/off times for HW with the boiler?
     
  7. plumberboy

    plumberboy Well-Known Member

    Has the new immersion heater got the correct length thermostat in it,just a thought.
     
  8. sam spade

    sam spade Active Member

    The cylinder is about 175 litres. Heating the cylinder from cold (20C) to hot (60C) using a 3kW immersion will take approximately 160 minutes and cost about 50p on economy 7. Gas is harder to calculate as it depends on the efficiency of the boiler. The break-even point is approximately 70%, i.e gas is cheaper if the boiler is more than 70% efficient.
     
  9. So it never was the case that the OP got a day's worth of hot water from a half-hour immersion...?
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice