Ideal Response 120 Boiler ...keeps blowing fuses

[AlexH]

I have a 4 year old Ideal "response 120" combi boiler that began blowing fuses yesterday morning...

The 3Amp fuse blows, I replace it, the system is fine for anything between 5 minutes and a few hours and then it blows again.

Both DHW and central heating run OK when the system is working, and I can hear the pump working fine...

Does anyone have any suggestions or similar experience ???

Alex H

 

[ChrisR]

Generally would look at the pump first. But look for signs of leaks from the main heat exchanger, getting to the electrics.

Hope yours isn't yet another 4 year old Response 120 to be scrapped because repair isn't really viable.

 

[AlexH]

The heat exchange is OK (I've heard of the cracking problems but it's bone dry inside) - I've got the manufacturer coming out in January (earliest they could do!) to fit the overheat trip swich that should extend the life of the h/e.

Pump appears fine....

Alex

 

[ChrisR]

It's corrosion, I believe, which gets the h/e's. Last one dumped had had full inhibitor dose, never overheated, did have the extra stat.

The only other common fuseblowers are fans and gas valves - if you can't see/smell anything there's not much you can do. Asked Ideal Tech?

 

[AlexH]

Just spoke to Ideal (after a lengthy hold!)...

Seems like a bit of a "classic" problem - the low water pressure switch needs replacing.

Has anyone had any experience of doing this or know how much this kind of job is likely to cost???

Alex

 

[Agile]

We carry the LP switch and regularly change them on the Responses. We charge £132 inclusive in London.

They would usually cause some dripping from the front right near the pressure gauge when they are leaking. When the boiler is working it tends to dry off the leaking water.

Tony Glazier

 

[AlexH]

I looked for any sign of leakage around the LP switch and couldn't see anything.

When I had the front open I noticed that the neon indicator for "Mains on" had blackened the surrounding area, and looked "burnt out" although it still functioned. I isolated the indicator and the boiler worked fine (DHW & CH) from Saturday morning until some point early this morning (around 6.00am ish) ...when I discovered that the fuse had blown again.

I tried to replace the fuse but it blew instantly...

Does this sound consistent with the LP switch or could it be something else??

 

[Agile]

If the LP switch is wet and has been arcing then its usually quite visable signs of destress. Its only two wires and you can detach them from the switch and join them together for a while if you can do that safely!

The indicator neons will attract dust electrostatically. Thats usual and causes no problems.

I am still expecting that if its not the LP switch then its the pump. If you were clever then you could disconnect the pump from the boiler and power it seperately from a mains lead fused at 3 A.

Tony

 

[ollski]

put a bit of kitchen roll under the low pressure switch to see if it drips, if it isn't the blue one it will do sooner or later.

 

[BDL]

You need to replace your water pressure switch.

The older style ones can actually internally and blow the fuse. The diaphragm has a small leak in it- as wtr gets into the microswitch the fuse blows.

The new ones are blue and longer with an extra 2 wires.