Baxi 105e Instant

mightysharfa2 · 30 Dec 2006

I recently fitted a 105e instant in my home, but oringionally wanted just the standard 105e.( Delivery mix up)
Does anyone know a way off having the water set to maximum heat and disabling the pre heat function in order to save gas consuption..? (As i am hardly at home.)
I know that if you set hot water dail off to 15 degrees, the preheat does not fuction, But this does not provide water at 65 degrees.
In a nut shell, I want maximum hot water, and don't mind waiting those extra few seconds for it, but don't want the pre heat function to operate on and off all day...... Any ideas....???????????

ChrisR · 30 Dec 2006

You could replace the store temperature sensor (I admit I'm not sure how it works, but there must BE one) with a fixed resistor whose value represents 60 degrees, so it always thinks the store is hot?
I'm sure Baxi wouldn't approve.

Slugbabydotcom · 31 Dec 2006

To confirm some of what ChrisR has said ...... From the MI's

3. The burner will light automatically and the temperature of the domestic hot water is controlled by the temperature sensor.

I would be on the phone to Baxi as I believe that in this mode it should kick out water at a min 58- 60ºC.
There could be a dip switch or potentiometer on the pcb that needs altering or you may have a faulty HW sensor if you are not getting anywhere near that.
An undersized gas supply could also have a big effect on HW temp in winter so its worth getting the working pressure checked by a corgi

gazthepottertonengineer · 31 Dec 2006

there is a jumper on pcb that could be removed to stop the preheat working cant remember which one of the top of my head but will get back to you

also its the central heating thermistor that controls the preheat temperature as its the central heating water thats stored in the expansion vessel and sent to the plate heat exchanger to give the initial burst of hot water

shouldnt use alot more gas anyway as it only kicks in when hot water taps turned on or heating is on

baxpoti · 31 Dec 2006

To disable pre-heat function remove jumper A10 or A11...... or both!

+++++++++++++++++++++++++++++++++++++++++++
ChrisR wrote:
You could replace the store temperature sensor (I admit I'm not sure how it works, but there must BE one) .

The 'store' is primary water, there is no stored dhw
therefore, you put cold mains water into a hot boiler and get instant dhw

doitall · 31 Dec 2006

We was alway told if you put cold water into a hot boiler you stand a good chance of cracking the sections.

Wonder if that has anything to do with the life expectancy of modern bean cans

Slugbabydotcom · 31 Dec 2006

shouldnt use alot more gas anyway as it only kicks in when hot water taps turned on or heating is on icon_confused.gif

I see where he is coming from.
If the preheat wasnt on then the boiler wouldnt light occasionally and the meter wouldnt go round occasionally.
If it saves £20 a year then that £20 could pay for a meal out or takeaway instead of eating egg and chips

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Baxi 105e Instant

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