3.15A Fuse blows on control board (Ravenheat RSF 820/20)

[sg1009]

I've read through some other posts on control board fuses blowing but I can't find anything definitive.

The control board has a 3.15A at the front and I think 500mA further around which is fine.

With a new fuse I ran the CH for 15 minutes and all seems well, flicked back to just HW, turned on the tap and within a few seconds the fuse pops.

I couldn't be sure but I would say that the water got excessively hot.

Any ideas?

 

[Dan Robinson]

Are you sure there is not a water leak in the boiler that is causing a short?

 

[sg1009]

Not something that I thought of. The electrics are dry in the control panel. I would have expected the main circuit breaker to trip out if that were the case. I will have a good look around in a minute.

Thank you for the reply Dan.

 

[ChrisR]

DO you have the manual?
Look for water on the diverter valve switch. You'll need a mirror!

 

[sg1009]

If I've got the correct part: Diverter it's a round thing 5 pipes out of it and electrics on the back. I lifted the small cover off it to and could see two grey micro switches. I've had a good look around the left hand (back) side of it with a mirror and a good feel around where I can with my fingers. All seems very dry.

Does this mean that it's more likely to be a part gone faulty?

 

[ItsOverFlo]

Could be faulty micro switch on circuit board.
A new board costs around £120

 

[sg1009]

Does anyone know if the electrics (ie. the micro switches and presumably actuators unplug from the back of the diverter? If they come off I can test the micro switches and replace them individually.

 

[Agile]

They are held on by a little clip but dont bother!

It can take 20 minutes to get it back on! Its not likely to be faulty!

You should be looking elsewhere for the problem.

I have not followed the thread but have you tried disconnecting the pump and seen if that stopped it blowing?

Tony

 

[sg1009]

Ahhhhh. Okay. Replaced fuse, disconnected the pump, powered on, ignighted boiler, ran the hot tap. Boiler fires up and hot water a pleanty! To complete the test I powered down and plugged the pump back in. The fuse is still in tact after running the hot tap a few minutes. Ahhhh!

I didn't realise the pump would be used with just HW. What would its purpose be, to regulate the flow?
Should I leave the pump disconnected and carry on a day or so?

Other observations during this test:
The water gets hotter the slower the flow.
The hotter the water, the more simmering sounds come from the boiler.

 

[Gasguru]

It may be worth changing the fan resistor. Its located on the right hand side of the combustion chamber at the back. It can be very difficult to get to with insufficient side clearance. I have had these resistors break down and allow leakage to earth via the casing.

The water will get hotter as the flow is turned down - there is always some lag as the boiler responds and "turns down the gas". A boiler this age is likely to simmer due to scale in the heat exchanger. The pump is used in hot water mode - it circulates water around the primary circuit of the heat exchanger and allows proper heat transfer to the domestic side water.

 

[sg1009]

Thanks for all your help folks. I had a plumber out last Saturday to look at the boiler. He found that the main boiler fuse was 13amp and is said it should be 3amp. This is why the 3.15amp control board fuse was popping. unfortunately he wasn't really that much more use. He started blaming surges from the main circuit breaker and recommended I get a electrician (his brother) out. I whisked him out the door on good terms.

After a week with the pump unplugged I haven't blown a single fuse. The gas keeps cutting out but I manage to get at least 30 seconds of water before it does.

Today I wired the pump up to a separate 3amp mains plug. After 15 minutes of CH and HW it popped. I replaced it again and, pop, the fuse goes again. This has got to be the pump! Any opposing views? Please tell me before I order one from somewhere.

I put an Amp Meter in series with it before it popped. It went from a steady 0.38 ish increasing to 0.45. I'm presuming the ammeter wasn't quite fast enough to display the peak 3A+.

Do I have to look out for anything in particular when buying a new pump?
The data on my pump is as follows:
Ravenheat
2,6uF - 400VDB / 230V-50Hz
III 2200 0.38A 88W
II 2000 0.27A 60W
I 1600 0.18A 40W
4506368 99/43 6
RS25/5-3
4506050
WILO

Steve

 

[staffs]

fan speed resistor shorting out to the casing is a common fault on this model. undo the fixing screws and remove it from the casing and then see if the fuse still blows. It is locateed at the back of the casing on the rhs about half way up .

 

[sg1009]

Today I wired the pump up to a separate 3amp mains plug. After 15 minutes of CH and HW it popped. I replaced it again and, pop, the fuse goes again. This has got to be the pump!

Sorry, I hate it when I'm ambiguous . The fuse in the separate mains plug pops not the boiler fuse, therefore the fault has followed the pump.

Looking on screwfix they have Wilo pumps and they look like they are rated RS50 and RS60. I'm only looking for a RS25 if that's what I need to go on?

 

[sg1009]

Could someone tell me if this is a suitable replacement pump:

http://www.screwfix.com/app/sfd/cat/pro.jsp?cId=102027&ts=88880&id=33590

 

[Dan Robinson]

No you need this:

456117 RHEAT 5009080 CIRCULATOR PUMP £72.11

that is from parts center with their part number on the left and Ravenheats in the middle.