BoilerMate2000 - hot water issue

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BoilerMate2000 - hot water issue

Post  Bablu on Tue May 14, 2013 8:25 am

Hi guys,

Not technical minded when it comes to boilers so forgive my ignorance but is there a way (or is it worthwhile) to turn off the heating supplied by the boiler (glowworm i think it is) to the hot water. As I understand, the hot water provided in these systems is the same as the cold water supply and it goes through the thermal store (boilermate 2000) to heat it up to around the 78degreesC mark, which is way beyond what I use in the shower etc, which is then further heated by going through the gas boiler. We have a big house and there are 10 individuals living here so I believe if this aspect can be turned off then it would be financially beneficial. The boiler would continue to keep the water in the thermal store at the 78degreeC mark(ish) but not waste further gas to heat this further for hot water. The showers in our house have the thermastatic controls and are set to 37degreeC so it seems a waste if the water is heated anything above going through the boilermate. I hope this makes sense.

I see there is a way to turn off the heating to the thermal store too when not in use but does anyone have any figures to show how much you save (wanting something similar with PV solar panels but no one seems to have these figures)? In this situation if the boilermate is off for say 6 hours, then the temperature would dip quite below the static control level meaning more gas is needed to get it to that level, while lesser gas is required to maintain the heat if switched on. So is the one large time spent heating up the water less costly then adding all the many small time spent heating up the water within the store?

Any other means by which savings can be made on this system would be greatly appreciated.

Thanks in advance and my apologies if my questions seem daft.

Bablu

Bablu

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Re: BoilerMate2000 - hot water issue

Post  feebet on Tue May 14, 2013 2:21 pm

Hi Bablu,

Through having a problem of my own I understand the BM2000 better now although I would not call myself an expert by no means !!

I think you're description of the operation is not quite correct and I believe it to be like this;

Boiler heats up the BM2000 on a normal boiler cycle. To achieve this the ACB has 2 LED's lit, one for the boiler pump and one for the boiler itself. With these lit the LH pump will run and power will be supplied to your boiler circuit board. Your boiler will then cycle on and off periodically until the thermal store achieves around 75 deg C. When this happens the 2 LED's will extinguish and the thermal store will sit there fully heated. Through natural heat loss the temperature on the thermal store will drop over time and the boiler will then be called for again to 'top up' the temperature in the thermal store.

Now if you switch on the CH, either via the timer or the room thermostat, providing the BM2000 is over 60 deg C, the third LED will light and the Middle pump will run, circulating heated water from the thermal store around your central heating circuit (through the radiators). As you do this the water from the store will lose heat as your radiators do their job. In conjunction with this the boiler will cycle again and the boiler pump will run because you are now asking the boiler to put heat back into the thermal store to overcome the heat loss from the radiators heating the property.

The third element is when you call for hot water. The hot water out of the taps is not actually the water inside the thermal store as this is contaminated with CH inhibitor etc. There is a heat exchanger on the outside of the BM2000 with a mains cold water feed. When you run the tap / shower the HW pump starts up after flow is detected and the cold water is heated in the heat exchanger by the hot water from the thermal store. Again, heat loss will occur in the hot water returning to the BM2000 so the boiler may again start to cycle to put heat back in the system.

I am note sure of the actual temperature that the HW is delivered but my unit indicated around 65-67 deg C, not the 78 deg C that you indicated.
When you mix this with cold water for your showers etc, obviously it is much lower - unless of course you have your shower mixer fully to the hot setting !!

So, in answer to your questions if I have understood them correctly is;

The hot water to the taps / shower is only heated when called for and is heated by already hot water in the thermal store. As the BM2000 is only around 75 deg C and you pass cold water through the heat exchanger, the hot water that you receive out of the taps must be lower than the 75 deg C from the thermal store due to heat losses / heat transfer. Someone may correct me but I believe current building regs say that there is a maximum temperature that the domestic hot water should be delivered at and I think this is 60 deg C ??

To turn the CH off, either turn the room stat fully down so the heating is never called for or switch the timer off. How much you save can only really be checked by looking at your gas usage on your bills. But bear in mind we are now over what was quite a cold winter so you will only see gains now anyway.

Personally, I would leave the BM2000 operating automatically and not turn off the heat source for long durations. I'm sue it is more efficient operating the way it is designed to do.

Hope this helps

feebet

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Re: BoilerMate2000 - hot water issue

Post  scorp on Wed May 15, 2013 1:49 am

Hello,

Here is my experience. I have installed dual timer on BM2000 so the second channel controls tank heating. Leaving alone situation when CH must be on, I have timer switching on BM2000 to bring the temperature inside the tank up for few hours a day, one hour in the morning and two hours in the evening. That is enough for shower and some domestic usage. If I need more then I switch it on manually. It significantly reduced my gas bill, from £60-70 to £30-40 p/m for 3 bed room house. If I need CH then obviously I switch on tank channel and CH one.
Here is the discussion:
http://gledhill-repairs.forumotion.net/t573-boilermate-2000-hot-water-operation
P.S. When I moved into my house it had been empty for about 4 months but agent left BM2000 running. I was surprised receiving gas+electricity bill of £200. That was just to keep storage within 60C-70C. That triggered me to think about new timer.

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