OSO direct unvented R20 heating element

[Clueless_Michelle]

Hi Guys,
I have a 5 year old OSO 20RD direct unvented water heater (powered by electricity) and the water is now running lukewarm to cold.
The installer has gone out of business but I'm told its probably the heating element - when I searched this forum it talks about two heating elements - but when I search online the only one sold is a single element

Oso 8015192 3kW Single Phase Immersion Heater - 240 Volts​

OSO don't open until Monday and their website only shows newer models not mine !!
Can anyone tell me whether this is the right part ? Does it take long for a professional to fit it ?Any other helpful advice would be gratefully received.
Love to all
Clueless Michelle

 

[oldbuffer]

Firstly, some afterthoughts which I should have put first!
A. Make sure there is power going to the heating element(s). I.e. the switches are on and the circuit breakers / fuses in the consumer unit are passing current.
B. If you have cheap rate electricity, make sure it is still connected. Earlier this year the time signal which told some cheap rate meters when to come on / go off was stopped, and the meters will no longer work reliably (if at all).

1. It may be the element, but it could be the thermostat.
2. The thermostat has two functions:
2.1 To turn the power to the immersion heater off once the water in the cylinder has reached the required temperature. Once the water cools the thermostat detects this temperature drop and automatically turns the power to the heater back on.
2.2 An overheat thermostat to turn the power off if the temperature exceeds a set amount (usually around 90 degrees). This is a separate part of the thermostat which does not automatically reset itself when the temperature drops. It has to be manually reset.
3. If you look at page 9 of the installation instructions (available at https://osohotwater.co.uk/wp-conten...l-20-series-RI-production-dates-2000-2010.pdf ) it shows a diagram of the thermostat at Figure 2. The reset button is clearly shown and is what has to be pressed to reset the overheat thermostat.
4. The thermostat is housed under a cover, see page 2 Figure 1 - General Layout. This cover MUST not be removed without isolating the electrical supply. If you feel confident:
4.1 That you can isolate the supply (I would suggest by turning off at the main consumer unit, or at all such units if more than one fitted); AND
4.2 Are aware that cheap rate power probably won't be available during all daylight hours so could come on suddenly while you are working: AND
4.3 And can be sure that it is isolated. NOT an electrical neon screwdriver but a proper voltage detector. THEN
4.4 Remove the cover and press the reset button. May fix the problem.
5. Because you have a direct cylinder, it is likely that you have two immersion heaters, each of which will have its own thermostat. The lower one will be connected to cheap rate electricity (if you have it) and the upper to normal rate electricity. The upper one is only intended to "top up" the hot water, whereas the lower one will heat the whole cylinder.

 

[endecotp]

I have a 5 year old OSO 20RD direct unvented water heater

Because of the safety issues with pressurised hot water, that may only be worked on by someone with the necessary qualifications.

 

[oldbuffer]

1. I believe resetting a tripped overheat thermostat does not require G3 registration.
2. However, the OP should note that an annual service should be carried out on any unvented hot water cylinder. This service must be done by a G3 registered person.

 

[Clueless_Michelle]

Firstly, some afterthoughts which I should have put first!
A. Make sure there is power going to the heating element(s). I.e. the switches are on and the circuit breakers / fuses in the consumer unit are passing current.
B. If you have cheap rate electricity, make sure it is still connected. Earlier this year the time signal which told some cheap rate meters when to come on / go off was stopped, and the meters will no longer work reliably (if at all).

1. It may be the element, but it could be the thermostat.
2. The thermostat has two functions:
2.1 To turn the power to the immersion heater off once the water in the cylinder has reached the required temperature. Once the water cools the thermostat detects this temperature drop and automatically turns the power to the heater back on.
2.2 An overheat thermostat to turn the power off if the temperature exceeds a set amount (usually around 90 degrees). This is a separate part of the thermostat which does not automatically reset itself when the temperature drops. It has to be manually reset.
3. If you look at page 9 of the installation instructions (available at https://osohotwater.co.uk/wp-conten...l-20-series-RI-production-dates-2000-2010.pdf ) it shows a diagram of the thermostat at Figure 2. The reset button is clearly shown and is what has to be pressed to reset the overheat thermostat.
4. The thermostat is housed under a cover, see page 2 Figure 1 - General Layout. This cover MUST not be removed without isolating the electrical supply. If you feel confident:
4.1 That you can isolate the supply (I would suggest by turning off at the main consumer unit, or at all such units if more than one fitted); AND
4.2 Are aware that cheap rate power probably won't be available during all daylight hours so could come on suddenly while you are working: AND
4.3 And can be sure that it is isolated. NOT an electrical neon screwdriver but a proper voltage detector. THEN
4.4 Remove the cover and press the reset button. May fix the problem.
5. Because you have a direct cylinder, it is likely that you have two immersion heaters, each of which will have its own thermostat. The lower one will be connected to cheap rate electricity (if you have it) and the upper to normal rate electricity. The upper one is only intended to "top up" the hot water, whereas the lower one will heat the whole cylinder.

Thank Yoooo Old Buffer, I wasn't expecting such a formidable response. What you have written is so clear that EVEN I can understand it. Thank you once again, for taking the time to impart all your knowledge - I shall be rolling up my sleeves tomorrow !!

 

[oldbuffer]

Please, only attempt it if you are absolutely sure of your ability to work safely with electrics. Mains voltage can kill you.