Hot Water Only Goes Hot When Central Heating Is On !

[GavinSnr]

Hi I have an Ariston combe heating system and its about 7yrs old ,the central heating works great but the hot water does'nt seem to ignight when central heating is off , I can control the water temp when heating is on so its not a thermostat as such ! I think this has been a graduall breakdown as this only happend now and again but now it only works when the heating is on it wasnst so much a problem when it was the winter as I just left the heating on but now time to fix it without getting my trousers pulled down by a big heating engineer anyone got any idea as so to be on top of any engineer who may have to fix it thanks

 

[MANDATE]

Hi Gav!.
As I understand combis, there is a heating side and a hot water side. On the HW side cold from the mains supply enters the boiler, then through a heat exchanger and comes out hot at mains pressure.
If the heating side is off and you open the hot tap something has to make the boiler flash up. Also with the hot tap closed something has to make the boiler stop. As far as I can make out it can only be one of two things.
There has to be a pressure switch or a flow switch.
When you close the hot tap, pressure on the pressure switch will increase and I assume break the contacts and stop the boiler, then when you open the tap it will release the pressure and make the contacts again and start the boiler. Or perform a similar function with a flow switch, but it operates on flow instead of pressure.
Thats the best I can do with my limited knowledge.

 

[ollski]

A hot water flow switch I should imagine....what model of boiler is it?
How far through the ignition sequence does the boiler get in hot water mode, does it start the fan?

 

[GavinSnr]

[/color[/i]hi there Ollski I'm so sorry for being 1 day late from getting your reply my model num is Ariston Euro combi sx 20 mffice,and there does'nt seem to be any fan running when I run the hot tap while heating is at off on the timer, I can only hear the water running through the system .thankyou if you can further pinpoint my problem although your first advise has been very much appreciated

 

[GavinSnr]

Hi I have an Ariston combe heating system and its about 7yrs old ,the central heating works great but the hot water does'nt seem to ignight when central heating is off , I can control the water temp when heating is on so its not a thermostat as such ! I think this has been a graduall breakdown as this only happend now and again but now it only works when the heating is on it wasnst so much a problem when it was the winter as I just left the heating on but now time to fix it without getting my trousers pulled down by a big heating engineer anyone got any idea as so to be on top of any engineer who may have to fix it thanks

Thank you also Author for your time between youself and Ollski I might be on to somthing again thanx

 

[GavinSnr]

Hi Gav!.
As I understand combis, there is a heating side and a hot water side. On the HW side cold from the mains supply enters the boiler, then through a heat exchanger and comes out hot at mains pressure.
If the heating side is off and you open the hot tap something has to make the boiler flash up. Also with the hot tap closed something has to make the boiler stop. As far as I can make out it can only be one of two things.
There has to be a pressure switch or a flow switch.
When you close the hot tap, pressure on the pressure switch will increase and I assume break the contacts and stop the boiler, then when you open the tap it will release the pressure and make the contacts again and start the boiler. Or perform a similar function with a flow switch, but it operates on flow instead of pressure.
Thats the best I can do with my limited knowledge.

Hi Mandate thankyou also for the time you have spent on analyising my prob but between youserlf and Ollski your advise seems to fit the bill as i do have a microswitch main flow switch again thankyou and together we will keep our trousers up