mysom midas si

[daz.boon]

can anyone help im after a manual for my boiler?
the led's must be there for a reason, are they to fault find?
problem being central heating pump has mind of its own, when switch off with timer switch is ok( pump doesnt run) but when hot tap switched on both pumps run you get hot water but ch pump runs and sends hot water to rads.There is a flow switch is that to stop the flow to the rads when hot water is switched on?

 

[Agile]

Sounds as if the DHW demand switch may have failed but it could be a relay on the PCB instead.

I dont see many of these nowadays.

Tony

 

[kirkgas]

i'm almost certain i have a manual in my garage, i'm off work tomorow so i will go and have a lok and see what i can find, can't do it now cause missus wants tea and toast!

 

[kirkgas]

can't find this manual in my garage, found plenty others though! if you still haven't got the prob sorted post again to let me know and i will have another look and ask the guys in work as well to see if i can come across one

 

[daz.boon]

thanks for quick reply kirkgas/agile yes still having problems boiler is pretty complicated.worked out central heating pump does switch off .but rads still hot as if still getting supply, found that hw pump led lights and pump runs as if something is requesting hot water but no taps on , if you feel ch return when this happens its very hot.could it be possable that the hw pump is back feeding rads? is there a valve stuck open without flow diagrams etc its hard work .Give me a engine to rebuild any day!

 

[kirkgas]

i will see if i can source the MI's

 

[daz.boon]

managed to download manual for boiler today!looked at flow diagrams what i think is happening is the hot water has a secondary heat exchanger which keeps a small amount of water hot for instant use but when it cools it makes hot water pump, to reheat it but it doesnt tell for how long it should be for? I would assume not long,but when this happens it seems to feed water back through the radiator return which according to the flow diagram is the wrong way ,there is no one way valve on diagram so would assume water pressure forces the water upwards to the main heat exchanger to be heated the only valve i can see is one below the pumps and are non return valves so what i think maybe the non return valve on the central heating pump is letting water back through so not enough pressure to stop back flow when hw pump runs