hot water, only with central heating on

[topbanana]

hello everyone , first question, but been using the site for a some time. helped me out on a couple of occasions
a friend has an ariston euro combi sx20 mfficetype c.
recently he tried to get hot water but the boiler refused to fire and send hot water unless he switched to central heating and hot water.
looked through installation instructions which gave possibilities as: diverter valve or micro switch.
does the fact he receives hot water at some stage rule out either of these or are there any other possible faults?
hopeful of result so i can hit him for a few beers

 

[kevplumb]

diverter valve or flow switch

 

[ChrisR]

Er, what flow switch?

Probably the diaphragm on't top end o' diverter valve. Should only cost a few quid. Takes a few minutes to change, but you have to drain some water out which is a pain.
You either trust the boiler's isolating valves which are very likely to give you trouble afterwards, or drain water (can be a LOT) from a drain off valve wherever it is on the system, and of course refill after. Suggest you turn all rads bar the one by the drain cock to save old water/inhibitor. Then the rad valves will probably leak....

 

[kevplumb]

alright the microswtch on the diverter valve

 

[topbanana]

thankyou both, i'll have a look at diaphragm asap chris and post response here.

 

[topbanana]

thankyou very much chris, diaphragm was nearly perished and rubber was stuck to bottom of unit at edges so no movement what so ever. fitted new one (cost £ 15 ), and hey presto hot water. many thanks again.