Apollo Gem & Megaflo - cylinder thermometer?

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  • bintyandthebeast
    Automated Home Jr Member
    • Feb 2013
    • 20

    Apollo Gem & Megaflo - cylinder thermometer?

    Hi all,

    I am looking at getting an Apollo GEM device to my house to divert all unused electricity from our solar pv system to be stored as hot water, but would like some assistance from anybody out there who can give advice please.

    The GEM device is detailed here: http://www.apollosolarproducts.co.uk...How_GEM_Works/
    We also have a 4kw pv system and LPG boiler which is used for heating and for charging the Megaflow 260 litre hot water cylinder.

    I turn off the LPG boiler for (hopefully!) 6 months of the year and instead I use the electric immersion for hot water on the premise that the excess generation from my pv system will reduce the cost significantly for generating hot water.

    My idea is that I get the Apollo GEM device and set it up as follows over the months which our LPG boiler is switched off:

    5am-6am - use the boost over-ride on the programmer to heat water to 60 degrees therefore using the minimum amount of paid for power to get to acceptable heating levels for showers in the morning
    6am-5pm - use the GEM device to store the tank up to 80 degrees therefore maximising the free power usage and minimising the cost of heating the water later in the day and the following morning
    5pm-6pm - switch back to the programmer to heat to 60 degrees so we have a suitable amount of hot water for dishes and the remainder of the night. This would obviously only kick-in if the stored water temp is below this.

    In the winter we would have the GEM device operating all the time at 80 degrees, with the LPG boiler heating to 60 degrees, therefore switching off the boiler when we are getting free solar power.

    I think this must be the most efficient way of running the device, but my question is this.....:

    Can I fit the temperature probe on/in my Megaflo cylinder to monitor this? It has a metal outer sheathing with insulation between this and the actual wall of the water tank. The paperwork for the GEM device states to stab the probe in to the insulation of the tank if possible, but would it be safe/advisable/possible to do this on my cylinder? If not, can i get a probe to do the same job?


    My plumber stared at me blankly when I asked his advice on this earlier today and I'm impatient to wait for the Megaflo manufacturer telling me that I shouldn't do it if I call them tomorrow!

    If anybody is interested, I have narrowed by choice down to the GEM device and SolarImmersion http://solarimmersion.co.uk/shop/sol...nergy-manager/
    But the GEM device is proving my favourite because:
    - the inbuilt programmer allows me to set the above times whereas the SolarImmersion device has a single on/off designed for use with Economy 7;
    - the thermometer probe allowance on the GEM device;
    - the ability to site the GEM programmer upstairs near the bedrooms/bathrooms for easier access rather than adjacent to my consumer unit which is in a low-down cupboard by the front door.
    - a 5 year warranty with the GEM device compared to 1 year with SolarImmersion

    Also, the GEM doesn't have issues with waves like Solar iBoost and Immersun devices which are very much frowned upon on all reviews (plus the GEM Will squeeze out power at a lower level than these also).

    The negative against the Apollo GEM is the fully installed price is a little higher than the alternatives, but I reckon the extra savings I would make using the variable temperatures and on/off times would sort this difference pretty quickly.

    Thank you all for reading this, I hope you can help.
  • heatingitaly
    Automated Home Lurker
    • Jan 2013
    • 8

    #2
    I've installed a few PV rigs in Italy and run a 4.6kWp array myself. While my comment might not be completely UK relevant it might be of some use to you.
    The GEM kit looks great and in principle looks sensible. I wonder though how much value your savings will have. I ask this because in the winter your panels output will be well under a third of their nominal rating while your background consumption will be about equal to that due to extra lighting etc. In summer the panels don't hit their rated output either because they hate heat. Let's face it there are a lot of other days in England when the panels won't be doing much either. I wonder then if running a low power immersion (say 2kW) every summer day just on a timer would be comparable enough and simpler than the GEM. I'd also lower the tank limits down from 80c which sounds excessive.

    Making hot water with a gas boiler in the UK costs a trivial amount compared to space heating

    Comment

    • heatingitaly
      Automated Home Lurker
      • Jan 2013
      • 8

      #3
      .... I might add that there is one system here that has a solar activated switch to engage the immersion heater. A garden PV light module is used to switch a relay so that whenever the sun is strong enough the immersion gets turned on. No further controls are needed as the immersion switches itself off with its inbuilt thermostat.

      Comment

      • bintyandthebeast
        Automated Home Jr Member
        • Feb 2013
        • 20

        #4
        Hi all,

        I just wanted to provide an update on my system now that it's been in for about a month.

        I used a metal kebab skewer to pierce through the insulation on my Megaflow using the secondary immersion access point and then wiggled the skewer to make the space wide enough to fit the probe down. I pushed probe pushed in to the new hole and secured the cabling, setting up the remainder of the system in a couple of hours (I installed a new socket installed next to my consumer unit as there was no space to fit the sender on the DIN rail). Overall, I'm happy with the unit, but I have had to make a change to how I used it:

        We are a large family (mum, dad, 3 teens and a 9 year old), so we were using in excess of a tank of water in the morning and the way it was set up we were running on cold water at the end of the morning washing routine. So, the programmer is set to come on from 6am to 9:30am to heat a tank at 54 degrees. It then switches to the max configurable 75 degrees until 4:30pm when we heat to 54 degrees (hopefully at this stage it's had enough free PV power to maintain it at a higher temp) and shuts off at 9pm til the next morning.

        All seemed to be going great guns, until I noticed a shortfall in the system. We had a couple of really sunny mornings a couple of weeks back and I popped up to the programmer to bask in the glory of it storing this free power by way of scorching hot water, only to see that I was actually exporting nearly 3kw and the system wasn't calling for any power. It turns out that when the GEM system is running on the programmer and it's reached the max temperature (in my case 54 degrees) there is nothing in the code to say that if power is being exported then divert that to the cylinder until the programmer clicked off and it returns to "optimising" mode. Crazy I thought, and thought of all of the pennies I was losing out on. So, I called the manufacturer and told them of my findings, after which I was transferred to technical support. They told me that the controller was updatable (real word?!) by the use of a portable programmer. He would look at the code and figure out an update to overcome this, thereafter sending a programming unit to me to update my controller! I was obvioulsy delighted by this news, but I guess only time will tell if they actually resolve this issue and send the programmer out. If they do, then I must say it will have been a fantastic experience from start to finish.

        I'll post again when and if I hear any more.
        Last edited by bintyandthebeast; 25 October 2013, 12:25 PM.

        Comment

        • bintyandthebeast
          Automated Home Jr Member
          • Feb 2013
          • 20

          #5
          I am delighted to say that I received a call from the technical support department at Apollo on Wednesday and I was told that there was an updated firmware for the controller based on my comments. I was asked whether I would be happy to do a firmware update on the controller and, as I answered positively, yesterday (Thursday) I received the update module. It clicked on, got power from my laptop and quite literally 3/4 seconds later had updated my controller. Best thing was that my existing settings remained undisturbed.

          If anybody is considering a hot water system which comes well packaged, has an excellent after care support system, comes with a 5 year warranty and is easy to install then I would 100% recommend you buy the Apollo GEM. I am absolutely convinced it is far and away the nest on the market.

          Comment

          • mbarlo
            Automated Home Lurker
            • Mar 2014
            • 1

            #6
            I'm new to PV. 10x Sunmodule SW Plus 250w mono black, SMA Sunnyboy 2500HF, Apollo GEM-D. Installed 21st Feb 2014.

            Just like to say the GEM isn't cheap but superior to other options. Even if it's a dull February day the GEM will feed something like 150w to 500w into the immersion heater, a lot better if the sun comes out. Not much but over a few hours it means the water is kept warm. With decent insulation (35mm) it stays warm and reduces the energy needed to raise the temp for morning showers - spiral in tank fed from central heating boiler.

            Any attempt to switch the immersion on by a simple switch that triggers in sunlight, results in using a lot of imported power to feed the immersion with 3000w. A lower wattage immersion would be an option, saving some importing of full price electricity, but even that wastes all day of low wattage when it's dull. The Gem is the answer.

            I also found ringing Apollo Solar for advice, resulted in good and patient answers.

            Martin

            Comment

            • seass
              Automated Home Lurker
              • Jul 2014
              • 1

              #7
              Wonder why Apollo Gem is gaining more votes in this thread as its alternatives are doing quite well. Agreed about Solar iBoost and Immersun's wave and flickering issues, although the respective makers have resolved them through service and upgraded releases. But SolarImmersion is reasonably priced and has most of the features of GEM except the guarantee and does the job well with a simple thermostat.

              Comment

              • HenGus
                Automated Home Legend
                • May 2014
                • 1001

                #8
                Originally posted by bintyandthebeast View Post
                Hi all,

                I am looking at getting an Apollo GEM device to my house to divert all unused electricity from our solar pv system to be stored as hot water, but would like some assistance from anybody out there who can give advice please.
                I do not want to rain on anybody's parade but when I asked a similar question on another forum I was advised to take note of the fact that the energy providers are looking to fit smart meters to PV solar-enabled properties as a priority to reduce export payments. The maths may still stack up for those with a 4KW array but I fear not for my 2KW system when the life cycle costs of these units are taken into account.

                Comment

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