Naked Science Forum

Non Life Sciences => Technology => Topic started by: richa on 19/02/2015 21:13:20

Title: Immersion heater expected overnight temperature drop
Post by: richa on 19/02/2015 21:13:20

Hi. Let's assume I have a well insulated, functioning, modern 300L immersion HW unit (clearly I don't but let's assume I did!), by how much should I expect the water temp to drop over night (between 6pm and 6am) given no hot water used, the cylinder is indoors and the inside temp is above 15 degrees C (i.e. its not freezing cold)?

I have just installed a temp probe and was shocked to find the temp dropped from 64 to 60 during this time period, with no HW used. I would have thought a 1 degree drop under these circumstances to be ideal. (I assume the probe to be working as it marries with water temp readings I did with a separate, manual water temp thermometer.

Any ideas? I'm asking what a reasonable good result would be for a 300L tank assuming no leaks, excellent insulation etc etc.

Thanks in advance.

Title: Re: Immersion heater expected overnight temperature drop
Post by: richa on 19/02/2015 22:03:59

BTW ... the probe is ⅔ to the top of the cylinder (⅓ the way from the top) and the one and only element is at the bottom of the cylinder. Cheers.

Title: Re: Immersion heater expected overnight temperature drop
Post by: syhprum on 20/02/2015 06:00:45

Why not just email the makers of this cylinder they will have the answer, if you don't like the result try other makes and see how well their cylinders are insulated.
There is a minimum standard for insulation 2.5kW/24hr heat loss requirement of BS 5615 1985 you need only to work out how much electrical energy is required to replace the lost temperature .

Title: Re: Immersion heater expected overnight temperature drop
Post by: richa on 20/02/2015 08:07:21

Thanks for that. I called them (Rheem) on a similar issue asking for some numbers and they were very evasive - I figured clueless, but might try again. Cheers.