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Author Topic: 'High Temperature' Immersion Heater  (Read 4304 times)
DaveF
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« on: May 01, 2015, 08:44:36 AM »

Hi All!

I'm looking to source a mains voltage immersion heater rated 2.5-3Kw which can have its thermostat set to 80 or even 85 degreesC. Anyone know where to find one?

Reason for this.....

I have 6.5Kw of grid tied solar PV which uses a Mk1 Immersun to heat my domestic hot water tank. Our domestic hot water demand is quite high-myself, wife, 2 kids under 4 (needing frequent baths) and a mother in law all drawing water from same hot water tank. Current immersion heater can be set to a max of 60C and I have a thermostatic mixing valve on the output to prevent anyone from scalding themselves from the hot tap.

In the summer, the system works quite well with the excess PV heating the hot water and my oil boiler switched to OFF for several months. However, if we get a run of cloudy or wet weather for a couple of days or more, the cylinder gets too cold to shower from or bath the kids so I'm basically looking at increasing the energy capacity of my hot water cylinder by increasing cut out temp of the immersion.

Anybody know of an immersion to do this?

Kind Regards,

DaveF
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paul149
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« Reply #1 on: May 01, 2015, 09:03:28 AM »

"hotter" is one way to go (with drawbacks ie scaling) but More Water ie bigger tank might be better? and is the current tank insulated to the max?

paul m.
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3.5 kWp (14 x Sanyo H250E01 + SB3000TL) 225' (SW) at 35' Pitch Lat 51.30' (Bristol) Installed cost 2.63/Wp (Nov 2011) now with solarimmersion and 250L unvented dhw (Almost Zero gas input for DHW from Apr to mid Sep)
Countrypaul
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« Reply #2 on: May 01, 2015, 09:12:26 AM »

You can re-range a thermostat this is done quite often for Bio making. Have a look at www.vegetableoildiesel.co.uk/forum as there are some threads on that covering the topic.
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biff
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« Reply #3 on: May 01, 2015, 09:53:03 AM »

I would go for a bigger tank with an indirect circulating pump, to take advantage of those long sunny days
    and store the excess hot water in a second tank which would be heavily insulated.
 It would work the same in winter with the excess boiler heat going into the second tank.

  Having the immersion located on top of a 6ft tank gives you immediate hot water and immediate recovery however, circulating indirectly to the bottom of the tanks means that you can heat the whole tank but still draw off as much hot water as you like. The circulating pump is thermo controlled,
  I would worry about setting the temp that high and trying to make the best use of the same small volume of water.
                                                              Biff
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An unpaid Navitron volunteer,who has been living off-grid,powered by wind and solar,each year better than the last one.
DaveF
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« Reply #4 on: May 01, 2015, 10:28:45 AM »

Hi All,

Thanks for the advice on replacing the tank but I'm looking at a relatively low cost fix-otherwise any savings in heating costs wouldn't be worthwhile.

I'm not sure of the volume of my current tank but I'm estimating 250l. Its about 4ft high, modern insulated stainless steel type with immersion about 1 third way up from the bottom.

Anyone able to suggest a suitable horizontal immersion?
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dan_b
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« Reply #5 on: May 01, 2015, 10:37:45 AM »

Does your tank have a boss for fitting an additional immersion at the bottom of the cylinder?

Worth putting an extra insulating jacket around the tank in any case - my tank came with the factory installed outer foam layer, but I have wrapped two extra jackets around it to keep all that lovely ImmerSUN-generated heat in the tank as long as possible!
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3.06kWp SolarEdge system with a split array:
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Mk1 ImmerSUN DHW diverter
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DaveF
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« Reply #6 on: May 01, 2015, 11:16:43 AM »

Hi Dan,

No Extra Boss on the tank already checked-but have an adhoc extra layer of insulation on the tank by way of an old king size duvet wrapped round it! (strangely the original seller of the duvet doesn't have any info on 'U' values on hand for it !!)

Regards,

Dave
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A.L.
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« Reply #7 on: May 01, 2015, 02:15:52 PM »

hello,

I'm not sure of the volume of my current tank but I'm estimating 250l. Its about 4ft high, modern insulated stainless steel type with immersion about 1 third way up from the bottom.

- more like 140litres if height accurate and tank (bare) diameter not more than 500mm
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Countrypaul
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« Reply #8 on: May 01, 2015, 04:33:02 PM »

This is the re-ranging article I was thinking of: http://www.graham-laming.com/bd/thermostat/thermostat.htm

IIRC you cannot adjust the setting of the thermal cutout, so if that is set too low (some I got were set to only just over 60C) it means the re-ranging is useless since the cutout comes in far too early.
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