SOLVED - 24/12 Vaillant Turbomax Blows Fuse When Fan Connected to PCB - Help!

[thereisnotry]

Hi all,

My Vaillant Turbomax 824e keeps blowing the 2A fuse when fan connected. It's fine doing nothing if the fan is unplugged and the boiler switched on.

Fan terminals at board connector read ~50K Ohms vs case ground. Is there a fan relay to check?

The fan seems to spin ok (without removing) not sluggish or seized.

Arrgh, Help! No hot water/heating for Christmas!

Do I need a new fan? Or a new PCB? What else to check before I waste limited cash? I have multimeter. It started for about a minute and a half this morning , the temperature reading went very high, like 110 degrees or something before dropping down low and then back up and pop went the fuse.

How can I see if the fan is working on startup? Should I hear it? I read not to remove the sealed metal cover when operating the boiler so how can I know if it's the fan blowing the fuse?

 

[Mikefromlondon]

Call a gas safe engineer and be safe, I wish you a Warm Merry Christmas.

 

[thereisnotry]

To give a little background...

This boiler has been in operation since 2002-3 (TurboMAX VUW GB 242/2-5 R1) in a relatively hard water area. Since I've been here (six months) the heating has been ok and the hot water started with hot/warm and progressed to warm/cold then only cold.

There were many occasions over the last two months when the system failed. A visit outside to the boiler showed either zero water pressure and a puddle by the PRV drain exit and once or twice a stupidly high 3 bar reading at which point the valve release was operated by me as an emergency measure to release the system pressure. Obviously, this couldn't go on. The system was being refilled often and of course, this would lead to further corrosion with inhibitor not being constantly added.

First gas safe engineer diagnosed EXPV failure. This seemed right to me given the over-pressurisation symptoms. Hot and cold DHW probably due to DHW H/E scale/blockage. Diverter valve probably same. Pipes underneath showing signs of leakage and corrosion where they connect to the end tails of boiler. Big job, wants loads of money - fair play.

So, I buy a brand new Vaillant Diverter Valve - £45 on the bay with seals/washers/clip.
12L EXPV Zilmet with filling loop and PRV £43.
Bunch of brass compression fittings and 22mm pipe with pipe bender. Say £50.
Treated myself to a Magnaclean 2 Pro for my troubles. £85

All fitted in a day - a lovely neat job that I'm not sure anyone else would have gone to the trouble to achieve since I had to get into a tight crawl space under the extension in order to cut into the pipe cleanly and provide a clear path for the rest of the install to the return pipe near the boiler.

After this I removed all the accessible hydraulics and descaled them. This list includes the diverter valve, the secondary DHW heat exchanger and the Vaillant Connecting Piece 018382, the manifold rear right behind the pump and all connecting pipes between them. All were descaled successfully and reinstalled with correct "packing rings" (Vaillant's proprietary name for O-rings and fibre washers). Pump O-rings changed also. No leaks. 18.2g of scale was recovered at a minimum from the DHW H/E.

So, my question is this.

If the system has been "run dry" for any length of time previously ie. the system pressure was zero (or rising to almost 3 bar and not noticed for maybe hours, until the rads are cold to touch) could the NTC on the hot flow pipe from main H/E (104597 connecting tube, cpl. with NTC-sensor) fail. Or do i misunderstand the concept of "running dry" which I only read in passing in another thread. Is it worth changing these sensors before a PCB swapout?

Could NTC failure lead to either a fan issue or, more directly, a straight PCB issue that could lead to a blown T2A.

At the moment, I'm grasping at straws. Tomorrow I will replace the PCB with a recond for £35 and report back any progress.

The second GSE says PCB because last night it was blowing the RCD at switch on. After a night of hair drying and sleeping with us in the bed the PCB is fully functional this morning but 10 seconds after any heat request the T2A fuse blows.

The PCB/Boiler remains powered on if the fan is detached. Pump seems ok when attached. It's just the fan for some reason.

And I, also, wish you all a very Merry and Warm Christmas.

/shiver.

 

[Agile]

Many would power the fan from a fly lead with a 3A fuse in the plug and see what happens then.

But a non gas safe person should not be replacing the fan.

As stated you should be getting a gas reg. engineer!

 

[bernardgreen]

Many would power the fan from a fly lead with a 3A fuse in the plug and see what happens then.

Fans that are variable speed may also need the speed control signals from the controller ( the PCB ) before they switch on their internal 230 volt circutry.

 

[Dan Robinson]

Fans that are variable speed may also need the speed control signals from the controller ( the PCB ) before they switch on their internal 230 volt circutry.

And is this a variable speed fan?

 

[bernardgreen]

And is this a variable speed fan?

Having googled the fan I can say, looking at the image, it is not variable speed.

 

[Dan Robinson]

Having googled the fan I can say, looking at the image, it is not variable speed.

So that e relevance and use of your last post was almost as pointless as your other advice on system design and underfloor heating.

 

[Agile]

"almost as pointless" seems to be an understatement!

I would have said "totally irrelevant and pointless"!

 

[jackthom]

Has the pump been running OK during your test with the fan disconnected. It's another candidate for blowing fuses and you did mention rapid overheating when the boiler fired up briefly.

 

[Agile]

The pump is another component where an independent 3A fused fly lead can assist.

That will enable the current taken to be measured.

I found one that pumping fine but taking nearly an amp, which with other boiler components resulted in the PCB fuse of 1.6 amps blowing after a while.

Tony

 

[ianmcd]

just get Vaillant out on a fixed price repair of £270 and it doesnt matter if it is the fan or the pump they will sort it

 

[thereisnotry]

Many would power the fan from a fly lead with a 3A fuse in the plug and see what happens then.

But a non gas safe person should not be replacing the fan.

As stated you should be getting a gas reg. engineer!

Yes, but the second G.S.E. said to change the PCB, which was wrong. I can't keep making costly shots in the dark. I just wanted a discussion about potentially already experienced issues with fans that could lead to a blown fuse.

Has the pump been running OK during your test with the fan disconnected. It's another candidate for blowing fuses and you did mention rapid overheating when the boiler fired up briefly.

Yes, the pump is running fine ostensibly. It made some gurgling noises to begin with, so I kept turning it off after 10 secs and releasing any pressure with the front screw valve. Eventually it setteled down nicely and is behaving well now, I think.

just get Vaillant out on a fixed price repair of £270 and it doesnt matter if it is the fan or the pump they will sort it

Yes, they are booked for tomorrow for £300. However, I would like to understand the issue myself. Everytime I rely on registered experts they are wrong. Go figure.

 

[thereisnotry]

Ok so update for anyone interested...


The windings on the fan motor looked burnt in one area, well, darkened if not burnt. This, and the fact it was blowing the T2A fuse was screaming change me.

Yesterday, I took out the old PCB as per the GSE's advice. He wanted me to buy a £250 board from Vaillant or his local stockist.

I ignored him and went to my local plumber's merchant and picked up a recond board for a lot, lot, lot less. Also picked up 3x NTC to replace the old ones.

I resisted buying the fan recond because of the Gas Safe Engineer's diagnosis.

I should have listened to my gut and bought it anyways. But it's no returns, so I didn't want to waste money.

Anyway, got the board home, swapped it out. Same as before. As I expected. Nothing wrong with original board, probably.

Phoned GSE to remonstrate his poor diagnosis. He's sorry to have cost me time and money.

Read and searched and read and searched all night, plotting to go get my fan today.

I did.

It worked. Sort of.

The switch out was no way near as hazardous as I was led to believe. It was as simple as observing and photographing everything I undid and removed and then following the procedure in reverse. The instructions are in the manual for the boiler.

I made sure the tubes were correctly seated - having checked they were clear inside of any debris and could blow through them when detached.

I made sure to connect the power to the correct terminals.

I slotted the fan in just as it came out and did everything up properly.

Bear in mind the boiler is in my garden in its own little hut, so the worst I could do would be to get the garden wet or blow up my line of sight shed. Or kill myself.

Checked and rechecked everything, connections, fittings, fuses.

Crossed my fingers and switched on. Hid behind hut door and used my inspection mirror to observe the LCD.

Success!

No blown fuse, pump started up, sounded like it was doing diagnostic startup procedure correctly.

Turned up the CH request to half way - fine. Started to light up the burner and saw the temperature rise to 60 degrees, could see the pilot flame start.

Stopped, put the outer case back on, tried again.

Starts up, pump going. Can't see flame with case on, but it didn't sound like it was lighting up.

Temperature started to drop, drop, drop to 15 degrees stable.

Tried hot water nothing. Stopped request.

Tried turning heating request up to max. No temperature change.

Hmm.


Checked gas valve is open underneath. Screwdriver slot socket is inline with the pipework i.e. open.

So that's where I am so far.

Any thoughts? Apart from get the engineer, he's booked.

By the way, I didn't fit the NTCs yet, in case anyone thinks their fitting is to blame.

I'm willing to consider diverter valve issue, since that was replaced since initial shutdown. But can't see why it would be that. Surely wouldn't affect the water temp.

Maybe an ignition issue, or gas pressure? Strange that the boiler is throwing no errors though? Shouldn't it be telling me what it's missing from its startup routine?

It's running and running, the pump is going but no heat is being produced. But it's not blowing the board fuse. Result.

I believe there is no flame starting. There is no Woomp sound like when it started normally in the past. If that's normal.

I'm going to read the manual and see if I can get the LCD to show gas pressure etc.

Thanks for the replies so far, really appreciate your advice and your concerns.

 

[Mikefromlondon]

Sounds like you will be having a Merry Christmas now.