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Running out of hot water - caused by Economy 7 supply probs?

Discussion in 'Plumbing and Central Heating' started by biped, 10 Jan 2009.

  1. biped

    biped

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    Hello

    I'd be very grateful if anyone has any suggestions as to what might be causing our boiler to run out of hot water constantly. I've looked online for information about it but haven't found out much, and we don't have a manual at home so I don't know how it is constructed inside or exactly how it works. I live in a pretty new flat - only 5 years old - and there used to be 3 of us living here but there have only been 2 of us for the last 6 months.

    We have a Megaflo DD210, a direct unvented cylinder. It runs on Economy 7, and for the last couple of months we have been running out of hot water on a regular basis. There's always hot water in the morning, but it just doesn't last much beyond about a five-ten minute shower (thankfully we have a second electric shower). We have a timed boost programmed for 2 1/2 hours late on an afternoon, which definitely works, and there's an additional timed boost programmed for 0230 - 0730, but as I understand it that would be overridden by the pre-programmed operational time which was set at installation. (I can't seem to access or interrogate the system as to what these master settings are, I can only see and alter the booster timings). These boost timings have been in place since we moved in to the property about a year ago, when we always had enough hot water. I have checked for switches in the airing cupboard which might have been turned off inadvertently, but the only one which seems to relate to the cylinder is the one which operates the booster.

    I noticed on my most recent electricity bill that the amount of night rate units used was a big fat zero! When I checked the previous bill, there were only 3 units used, but I had not spotted it at the time. The bill before that it was over 400 night units, so I am guessing that the problem arose just after the start of the previous bill. I rang our electricity company, who agree that there must be a fault with the meter, and they are sending someone to check it this week.

    I've been taking three meter readings a day over the last week, including one last thing at night and one first thing in the morning, and the number of units consumed overnight, which clock up on the daytime meter, is 7. That's with no heating running (everything is electric here) overnight, only the fridge and hot water cylinder. When the flat is empty for the day, only 1 or 2 units are typically consumed for that whole period, so I can confidently assume that it is the cylinder racking up the night-time use on the day meter.

    My question is this: If our night rate supply has not been working for some months, as our bill would indicate, how exactly would this have been affecting the cylinder operation? Clearly we are getting hot water somehow, but if it is purely because of the extra timed boost at 0230-0730, why are we now running out of water so often when, a year ago, the system ran properly via similar hours of operation (albeit presumably via the proper installation settings and a working night electric supply) yet we had enough hot water to last 3 people all day.

    It seems far too coincidental that the hot water has been problematic for about the same amount of time as the night time electricity supply has been playing up, but it is just a lack of night electricity from the meter that is at fault, or could it also be a fault with the boiler itself (ie it hasn't been drawing on the night-time supply?). I can't see how it is the boiler, as I would have thought that any use of electricity in the flat after 2230 should be clocking up on the night-rate meter (apparently our night rate applies from 2230-0030 and 0230-0730), and clearly it hasn't been - and my meter readings prove that the night use is clocked up on the day meter anyway.

    I am wondering whether it might be that there are two separate tanks in the cylinder - one large capacity one fed exclusively by night-rate electricity for the main night-time operation and a smaller one for daytime boost, fed exclusively by daytime rate supply. If the night-time one is effectively out of action altogether because of the electricity meter fault, then it is only the smaller daytime tank which is ever being heated, even when the extra programmed 0230-0730 night boost is on, and that therefore explains why we are running out of hot water so regularly. Am I a million miles off there? This is the info I've been trying to find online but have not been able to.

    I have asked our landlord about how the system works but he is clueless, and I can't see him agreeing to get someone out to check the boiler unless I can prove exactly where the problem lies. I am going to wait to see what EDF's electrician says on Wednesday, and take the opportunity to pick his brains about the boiler whilst he's here. If he fixes the night rate supply and the boiler starts giving us a plentiful supply of water again then I know it was the fault of the meter, but I am just very puzzled as to why we are effectively heating the water for similar hours to what it should be, yet running out of water so often.

    Many thanks in advance for any suggestions
    Adele
     
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  3. Softus

    Softus

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    Have you tested the off-peak immersion element and thermostat?
     
  4. biped

    biped

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  5. biped

    biped

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    I wouldn't have a clue how to do that - I am about as far as it gets from being DIY-savvy. And I don't think my landlord would thank me for trying! I hope this doesn't mean I'm inappropriately using this forum.

    I'm really just trying to figure out what the possible causes are before I ask my landlord to get the boiler fixed. It may well be that fixing the night-time electricity supply is enough.

    Our hot water is VERY hot though. Might this also be clue?
     
  6. Softus

    Softus

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    But isn't that why you're here?

    Do you know anyone who has a multimeter?

    In that case I really don't understand why you're here.

    Why? Why do you need an entire list of possible causes if you're not going to be the person diagnosing or fixing it?

    Well then, test the thermostat. Or get someone else to.

    You seem to be approaching this as if it's a game of Cluedo.

    It isn't.

    Your system is a collection of integrated but discrete components, each of which is capable of developing a fault, and each of which can be tested for correct operation.

    Writing a novel about it won't get you anywhere.
     
  7. biped

    biped

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    Hi Softus

    I am here because I would like to understand my heating system and what might have gone wrong with it. I am interested in how stuff works, and when it goes wrong I like to at least try to get an understanding of why. As I said at the very start of my post, I am simply looking for suggestions as to what may have gone wrong, and am grateful to anyone who takes time to respond. That includes you.

    If it were my system then I would get in there with a multimeter and have a go. I have certainly used one before. As a tenant I am unfortunately not a position to start pulling my boiler apart, and with a difficult landlord I know I stand a better chance of convincing him to get someone in if I can point out what the likely cause is. Hence my post.

    I read a number of forum posts first before deciding it seemed to be within the spirit of this forum to ask a general 'what do you think might be wrong?' question. Someone describes the symptoms of the problem, what they have tried to do to pinpoint the cause and other people respond with suggestions as to what the problem might be. I would rather you just ignore my post than get hostile because I can't actually fix it myself. There are plenty of other posts on this forum where people are just asking for a bit of help to diagnose a problem.

    Best wishes to you
     
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  9. Softus

    Softus

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    You haven't given enough information, but it's likely that you have an electrically heated cylinder, with two immersion elements.

    If the temperature is too high, then it's a thermostat problem.

    If the temperature is too low, then it's either faulty thermostat, or faulty element, or too short an 'on' period.

    If the temperature is fine, but the quantity insufficient, then it's either too short an 'on' time, or the position of the heating element being used isn't low enough, or a faulty element, or a faulty thermostat.

    That isn't how diagnosis works.

    Really? How do you reconcile that statement with your claim of not having a clue?

    You don't have a boiler, or at least if you do you're keeping it, and it's make and model, a closely guarded secret.

    Frankly, if I were your landlord (and I happen to be one) then I'd prefer you to report symptoms promptly, accurately, and succinctly, and not waste your time and everyone else's by attempting a diagnosis.

    Your post, since you've referred to it, contains things that you contradict in your later posts. For example, at one point you appear to want a full list of possible faults, and now you claim only to want the "likely" cause.

    Likeliness of cause of utterly irrelevant. By definition, the perceiver of any given "likely" cause will be mistaken at least some of the time. The only worthwhile goal is one of certainty. If you don't want certainty, then you want uncertainty, and if you want that then you're wasting time and effort.

    I don't do "suggestions".

    If you don't want a diagnosis, then you'd be best off ignoring my posts and waiting for someone else to post.

    If you want to know how the forum works, then read this topic:

    http://www.diynot.com/forums/viewtopic.php?t=6026

    At no point have I felt any hostility, and I choose not to ignore your posts.

    And a bit of help is what you've had - you're just unwilling to follow the correct process of diagnosis, and you mistakenly think that something can be achieved just by yacking.

    You won't get anywhere whatsoever without testing all immersion elements and all immersion thermostats.
     
  10. Slugbabydotcom

    Slugbabydotcom

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    Its an unvented cylinder and only those with G3 tickets should be touching it.
    What I can advise you to do is to check that whoever comes to fix it has a card to say they are competent to work on it. Look for the letters UDHW which means unvented direct hot water. I am registered with ERS [european registration scheme] CITB is another certifying body and there are others
    What you need to watch out for is a muppet trying to link out a thermostat.
    The problem lies around the lower of the two immersion heaters. The supply timer/switch is a likely culprit as are the thermostats and the element itself. One of the stats is re-settable by way of pushing a button in. Any unqualified tampering should be restricted to re-setting as a one off[With the power off of course]. After that then the question of why it keeps tripping needs looking into by an expert.
    To see why I am rattling on about this so much check out the video HERE At 210 litres your 'bomb' could be 4 times bigger than the one in the video
     
  11. biped

    biped

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    Thankyou slugbabydotcom, that's useful advice. And that video!

    I'll make sure only a qualified engineer gets to test our cylinder.

    Do you think that if our electricity meter is sorted out and the night rate of electricity is restored by our electricity supplier this week, and the hot water supply returns to normal afterwards, that we should still ask for the cylinder to be checked? Or are we safe enough to assume that it was just the lack of night rate electricity to the lower immersion heater that was the cause?
     
  12. Slugbabydotcom

    Slugbabydotcom

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    Correct.

    I could be wrong but I do suspect your problem is further down the line as per my previous post. I tend to find that some of the timers have been causing problems. Seeing as these are switching a 3kw supply, bad design has meant that I have been called to several faulty ones. In 2005-6 I fitted 14 unvented cylinders and every single one of those timers has since had to be changed. I am just glad I left the cylinder wiring to the electricians on that job.
    Nothing wrong though in checking your fuse box to see if something has tripped. I would suggest that it will be a 15 - 20Amp fuse or MCB that has gone if any.
     
  13. Softus

    Softus

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    The cylinder doesn't need testing. :rolleyes:

    The meter fault is merely a theory at the moment.

    Ditto.

    Checked for what?

    Don't assume anything. You really do have the most bizarre approach to this.

    When you've checked the MCB (although I can hardly believe that you would have created this topic without checking it first), then get your meter out and test the elements, then you will have eliminated those. When all the obvious causes have been eliminated, then whatever remains, no matter how improbable, must be the cause.
     
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