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Alde 2928 boiler blowing fuses


DJW
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We have an Alde upright 2928 boiler which we haven't used recently due to a plumbing leak. I drained the central heating system and have finally got round to repairing the leak and refilling the system.

 

When I went to turn the circulation pump on it didn't start. I eventually found a blown fuse on the positive supply cable to the boiler. Having replaced it, the fuse just blows again so it appears there is a short circuit somewhere.

 

Does anyone have any idea where to start looking? I've checked for anything obvious like chafed cables shorting on the boiler's housing but can't see anything.

 

The positive side fuse is 5A (interestingly the manual suggests 1A...) there is also a 1A fuse on the negative supply cable (as per the manual). The boiler is also fitted with a Danfoss room thermostat wired per the instruction manual.

 

I'm a bit stumped - any suggestions?

 

Thanks

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Can you spin the pump impeller by hand? Try running the pump out of the header bottle to see if it's jammed?

 

Does it blow just trying to spark the boiler with the 12/240 selector switch on the boiler set to the middle position so the pump is isolated?

 

Cheers

 

Gareth

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Sorry, I should probably have said the fuse blows as soon as I connect the 'chocolate box' type connector to the top of the boiler (i.e. as soon as the power supply circuit is complete) - the pump doesn't have to be switched on for the fuse to blow.

 

I have checked the pump and it spins freely so that should be fine if I can identify the short.

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Have you checked there isn't any liquid in the switch panel from where you refilled the system?....it's easily done to splash a bit as you fill it up.

 

I take it all was good before you drained it and nothing had changed in the wiring?

 

Cheers

 

Gareth

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Ours doesn't have the 12/240 selector switch you mentioned. The only controls on the boiler itself are the combined spark/temperature knob but I will have a check for moisture around all the wiring, good idea.

 

We haven't used the boiler in ages (partly due to the CH leak) but we did fire it up about six months ago for our boat safety inspection and it was fine then and we haven't (deliberately) changed anything since.

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The normal technique for finding the cause is to get a good handful of new fuses then disconnect everything you can see/think of inside the boiler, (pump, gas valve, PCB etc) then bung in another new fuse and restore the power. If the new fuse still blows then you've ruled out a lot of parts and more of the boiler needs disconnecting. If you're down to the loom only and its still blowing fuses its then time to inspect every inch of the loom closely for damage.

 

If the new fuse doesn't blow then turn the power OFF, reconnect one item then turn back ON. See if the fuse blows. If not, connect the next thing and so on, until reconnecting something blows the fuse. Then you've got it!

 

MtB

Edited by Mike the Boilerman
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First make sure the switch on the thermostat is turned off, that isolates the pump circuit. If it still blows then my guess its wring on the boiler itself which is fairly simple once you get you head around it. Any chance a wire has been trapped between a cover the the boiler body sheets?

 

I have just had a look at the manual and the fault finding chart says nothing about blowing fuses.

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Thanks for the replies all.

 

Mike - I followed your advice about isolating individual components and have tracked the fault down to something to do with the thermostat. So I've disconnected that and it now works just manually switching the pump on/off. That's fine for now at least.

 

Now for the next problem!

 

 

Part of the reason we rarely used the boiler is because it's always been extremely ineffective at actually heating the boat. I always put this down to sludge in the system so whilst I had it drained down I removed the radiators and flushed them through with mains water. A fair bit of sludge came out so I thought we'd be in business when I got it all working again.

 

Unfortunately it's as useless as it ever was!

 

The system from the boiler is: large lounge radiator --> calorifier --> small corridor radiator --> small bedroom radiator --> very small bathroom radiator --> return to boiler

 

The lounge radiator gets warm to half way along and one side of the calorifier coil is luke-warm to touch. Other than that the system is stone cold. The flow pipe from the boiler is very hot, the return is stone cold. I've bled all the radiators but 1/2 a warm radiator is the best we seem to get.

 

I notice from the boat-specific Alde manual that they suggest boats over 55' might need a separate circulation pump to help out the one built into the boiler. Our boat is 57' and has the system as above. Is the standard pump to blame for the poor performance?

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Thanks for the replies all.

 

Mike - I followed your advice about isolating individual components and have tracked the fault down to something to do with the thermostat. So I've disconnected that and it now works just manually switching the pump on/off. That's fine for now at least.

 

Now for the next problem!

 

 

Part of the reason we rarely used the boiler is because it's always been extremely ineffective at actually heating the boat. I always put this down to sludge in the system so whilst I had it drained down I removed the radiators and flushed them through with mains water. A fair bit of sludge came out so I thought we'd be in business when I got it all working again.

 

Unfortunately it's as useless as it ever was!

 

The system from the boiler is: large lounge radiator --> calorifier --> small corridor radiator --> small bedroom radiator --> very small bathroom radiator --> return to boiler

 

The lounge radiator gets warm to half way along and one side of the calorifier coil is luke-warm to touch. Other than that the system is stone cold. The flow pipe from the boiler is very hot, the return is stone cold. I've bled all the radiators but 1/2 a warm radiator is the best we seem to get.

 

I notice from the boat-specific Alde manual that they suggest boats over 55' might need a separate circulation pump to help out the one built into the boiler. Our boat is 57' and has the system as above. Is the standard pump to blame for the poor performance?

 

Wjhen the boiler was refilled, was the antifreeze mixed thouroughly with the water before filling? In most systems, the rads rely on the tiny density difference between the hot and cold water to get the water to circulate within the rad. If there is a slug of water with more antifreeze in it sitting in the radiator due to not being well mixed beforehand, it will stop the circulation within the rad.

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Thanks for the replies all.

 

Mike - I followed your advice about isolating individual components and have tracked the fault down to something to do with the thermostat. So I've disconnected that and it now works just manually switching the pump on/off. That's fine for now at least.

 

Now for the next problem!

 

 

Part of the reason we rarely used the boiler is because it's always been extremely ineffective at actually heating the boat. I always put this down to sludge in the system so whilst I had it drained down I removed the radiators and flushed them through with mains water. A fair bit of sludge came out so I thought we'd be in business when I got it all working again.

 

Unfortunately it's as useless as it ever was!

 

The system from the boiler is: large lounge radiator --> calorifier --> small corridor radiator --> small bedroom radiator --> very small bathroom radiator --> return to boiler

 

The lounge radiator gets warm to half way along and one side of the calorifier coil is luke-warm to touch. Other than that the system is stone cold. The flow pipe from the boiler is very hot, the return is stone cold. I've bled all the radiators but 1/2 a warm radiator is the best we seem to get.

 

I notice from the boat-specific Alde manual that they suggest boats over 55' might need a separate circulation pump to help out the one built into the boiler. Our boat is 57' and has the system as above. Is the standard pump to blame for the poor performance?

 

Don't know how your Alde is plumbed in but this is what we found.

 

When first using our Alde, it would take more than two hours to get warm rads.

Now, we turn the valves to by-pass the calorifier, turn on the Alde and the rads are hot in about half an hour.

Once we have hot rads we then open the valves to the calorifier to get hot water.

We now have hot rads and hot water within an hour.

 

Rob....

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Wjhen the boiler was refilled, was the antifreeze mixed thouroughly with the water before filling? In most systems, the rads rely on the tiny density difference between the hot and cold water to get the water to circulate within the rad. If there is a slug of water with more antifreeze in it sitting in the radiator due to not being well mixed beforehand, it will stop the circulation within the rad.

 

This generally happens with a one-pipe system but not a two-pipe.

 

 

 

 

When first using our Alde, it would take more than two hours to get warm rads.

Now, we turn the valves to by-pass the calorifier, turn on the Alde and the rads are hot in about half an hour.

Once we have hot rads we then open the valves to the calorifier to get hot water.

We now have hot rads and hot water within an hour.

 

Typical behaviour for a two-pipe system, less so for a one-pipe.

 

Best if the OP identifies which he has before we proceed...!

 

 

MtB

 

 

 

(Edit to sort out my completely messed up post!)

Edited by Mike the Boilerman
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take a look at the top of the pump - the wire is incredibly easy to pull (especially if you let the pump dangle from its wires while you fill the expansion tank), causing the insulation on the wire to come away from the metal, and thus it shorts out. Replacement pumps have the wiring "protected" slightly from this issue by having a short loop fixed to the pump with a tie - means you can let the pump dangle from the wire and not pull the wire out.

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This generally happens with a one-pipe system but not a two-pipe.

 

 

 

 

Typical behaviour for a two-pipe system, less so for a one-pipe.

 

Best if the OP identifies which he has before we proceed...!

 

 

MtB

 

 

 

(Edit to sort out my completely messed up post!)

 

 

Right, sorry for the delay Mike (too busy boating!) but I've done some homework and it appears we have a one pipe system.

 

dor - I thoroughly mixed the antifreeze/water solution in a container before refilling the system so I'm happy that it's mixed properly.

 

ROBDEN - Interesting and to be honest I probably haven't run the boiler for two hours to try it given how little heat we got into the rads in the 1 hour or so I tried it for the other night. Unfortunately as it stands we can't isolate the calorifier from our system. The radiators all have valves to close them off and just heat the calorifier but you can't do it the other way around.

 

 

Just to add a little more complication, whilst cruising today I turned the circulation pump on (without the boiler running) and *all* the radiators got warm (the bottom half anyway), suggesting that the pump is circulating properly and distributing the heat from the domestic hot water around the CH system via the calorifer coil.

 

I wonder if it's possible an air lock has worked its way out somewhere (the level in the boiler's header tank has dropped slightly). It's too warm here right now to fire the boiler up but I will give it another go tonight and see if the radiators get any hotter than last time I tried it.

 

Will report back again once I've run the boiler for a bit.

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Time for tonight's thrilling update!

 

It looks like there was an air lock in the system which has worked its way out by running the pump. I've had the boiler on for an hour and a bit and the pipework is all nicely hot. The lounge radiator is belting heat out, the others are only warm as they are the far side of the calorifier, which I assume is taking a lot of heat out of the system as suggested by Robden, so will probably take a lot longer to get properly hot.

 

Two of the radiators were only warm at the bottom so I tried bleeding them and the bleed water (not air) was virtually clear so presumably some old water left in the pipework which I didn't manage to flush out. Dor - I think you were right actually, I've bled as much of the clear water out as I can and topped up the header tank steadily with fresh water/antifreeze mix and the radiators are getting warm right the way up. Unfortunately I've run out of antifreeze so I'll have to finish the job another time!

 

I think in time I might add a bypass option for the calorifier as suggested by Robden so we can get the radiators hot quicker.

 

So a team effort from the forum - thanks to all for helping out :)

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