Blowing fuse

[Spottyfrog]

Hi guys, before I start explaining my problem I would like to say hello to everyone as I’m new to this forum.

Problem:

For some reason the 3A feed fuse to my gas central heating kept blowing. I worked out that it only happened when I switched with the switches on the programmer. (ie hot water on constant or heating on, although this didn’t always happen)

For some reason the switches on the programmer now have no effect on whether the heating/water is on. In fact the only way to turn the heating/water on and off is to switch the switch on the feed spur.

I checked the 3 port valve (Danfoss HSA3) which was stuck in the central position. If I use the arm on the side to change from auto > man the 3A feed fuse blows.

I have come to the conclusion (GUESS) that the 3 port valve is the cause of this problem. Please can anyone more qualified shed some light on my situation.

I have found this problem difficult to explain so apologise if this post is in anyway confusing.

Thanks in advance.

Spottyfrog.

 

[corgiman]

is your pump wet?

 

[simond]

You may need someone qualified and electrically savvy to look at this.

The first thing I would do is temporarily disconnect (and insulate) the orange wire on the flex from the Danfoss valve. This is the live feed to the pump and boiler.

run the system up again and try moving the man/auto handle. My guess is that the fuse won't blow. If it does, it will almost certainly be valve actuator head. If it doesnt, there is a problem with the boiler or wiring to the boiler and pump. Can't be any more specific because you have (yawn!) not told us what boiler you have.

The reason the programmer is always on is almost certainly because you have welded the contacts on by connecting a dead short circuit to them. Better add a new programmer to the shopping list.

 

[Spottyfrog]

Thanks for your quick replys guys.

I have a baxi solo boiler. Sorry i didnt mention in earlier post.

Regards,
Spottyfrog.

PS. My pump is not wet and no evidence of leaks in past.

 

[ChrisR]

If the valve is stuck in the middle it's a fair bet that it's leaking at the spindle, and the water from there has got inside the head. Remove the head (2 screws) - if the plate's rusty, change the whole valve.

 

[Softus]

The symptoms are also consistent with a faulty pump.

You can easily test it by disconnecting the pump flex and putting on a plug (with a 3A fuse in) to power it - isolate everything electrically first.

If not the pump then it could, as people have already said, be the MZV.

Also, I've seen the same symptoms where the electrical supply to the boiler was chafing at its point of entry through the boiler casing - the fuse went at the moment that the boiler was activated.

 

[Spottyfrog]

I totally disconnected the 3 port valve from the system. I then turned the system on (the boiler fires and the pump starts working THE FUSE DIDN’T BLOW). I also removed the actuator on the 3 port; the head is clean with no sign of leakage.

Thanks again for your fast responses.

Regards,
Spottyfrog.

 

[Spottyfrog]

Ordered New 3 port valve actuator today, ill post to let you all know how I get on, Thanks.

 

[Spottyfrog]

Fitted new actuator today, all is fine. Thanks for your help guys.