Ideal Mexico Super CF40...

[MattChan]

Just moved into a place which has one of the above boilers fitted (around 1986) with a flue that runs from the kitchen vertically up through pre cast concrete blocks and then in the roof space it changes over to tin ducting which runs at 45deg and then pokes up out the roof!

By the looks of the docs it was last serviced around 3 years ago!

When the main burner lights up there are tinges of yellow in the flame, is this normal or do I need it looked at?

Another functionality point is I'm getting plenty of hot water but when I tried to run the central heating only the main burners never fire up even though the thermostat is demanding it.

If I were to have this unit replaced what sort of thing should I go for? Something like a Worcester Bosch Greenstar 15Ri? Would this cope ok with the verticle fluing?

Any advice greatly appreciated

Matt

 

[Agile]

It seems that you have a fault with the motorised valve!

Although its a few years old its very reliable but perhaps only 78% efficient compared with 92% from a modern condensing boiler.

You need to consider the gas bill to decide if there is any advantage changing to a new boiler. If its less that £800 pa its better keeping it!

I could not have suggested a better replacement myself !!!

Tony Glazier

 

[MattChan]

Thanks for the speedy reply mate!

Would the motorised valve stop the burners firing up when I only select CH and not HW?

Its costing me about 13 quid a month at the mo! Have to see how much the bills go up over the winter!

 

[bster]

yes

a microswitch within the motorised valve is (normally) activated and this sends a signal to the boiler to fire up on CH. A HW demand only though, will send the signal to the boiler from the programmer then to the cylinderstat thyen to the boiler.

 

[MattChan]

I'm guessing I have what's called a Y plan system in the manual for the boiler with a 3 port valve, pump, room and cylinder stat?

In the small print it says "CH cannot be selected without HW" so it seems I may have just misunderstood how the system opperates as that is exactly what I was trying to do!

 

[MattChan]

Just been looking over the schematics for the Y plan system on the net and in the boiler manual. They seem to differ slightly!

As per the Y plan diagram in the boiler manual it would appear that I don't have a HW OFF pin on my programmer. When you only select CH the 3 port valve doesn't get powered by the grey wire to wind it's self on to the CH only position. Because the valve never reaches the CH only position the boiler is never powered by the orange wire!

The Y plan diagrams on the web have the HW OFF pin on the controller connected to the Grey wire on the 3 port valve which lets the valve move on to the CH only position when only the CH is selected.

Are the two different wirings of Y plan both common? Or is my install obscure?

Can I just replace the programmer and add the additional wire? Is this electrical work notifiable?

 

[bab]

Are getting heating at all. if the syncron motors go on ya y plan valve u will still get hot water but it wont switch off by the cylinder stat & you wont get heating at all.

 

[MattChan]

It all performs perfectly if you switch the HW and CH switch on on the programmer. If either of the stat's demands heat it fires up the boiler and the valve flips over to the correct location!