Baxi Duotec HE40 Problem

[russ2m]

Hi, hope someone can help. In the summer a radiator got taken out and two valves ( the thermostatic value and standard) got switched off. A new Radiator was meant to go in pretty quick but didnt.

We were stuck away the other night in snow and came home to find some water had leaked out of the thermostatic valve. I have since learned it didnt have an"off" but instead a frost position which allowed water through when it got cold enough.

The problem comes with not knowing what happened while we were away. The house obviously got cold enough for the boiler to fire. The system was part or fully empty of water (not sure which)

The end result is that we came home to find the live side 2a fuse blown and the system empty. I have spent some time following the instruction whilst in the loft to A) re-pressurize the system and B) replace the fuse.

It is still blowing fuses and I am concerned the pump may be damaged. its a grundfos 15-60

so my questions area as follow.

> does this boiler have dry running protection and as the boiler is at the top of the system would this have cut in quickly. (is this why the fuse is blowing)

> now the system is full how should the pump be set. ie should the screw in the auto bleed valve be closed or open etc?

Many Thanks in advance for any help of guidence you might be able to give

Russ

 

[rojaca]

boiler should have gone to a low pressure lockout. e119. I would suggest that the fuse being blown is a seperate fault.
Only if you are competent/confident and you are able to prove safe isolation, you should do the basic dead electrical safety checks. Earth continuity, short circuit and resistance to earth.
Short circuit is usually approximately 450 ohms
Resistance to earth should be >10Mohms. (usually >20Mohm)
Earth continuity <1ohm

You should undertake these prior to carrying out any electrical work.

 

[russ2m]

Hi Thanks for the reply, I have done the electical test and everything seems ok.

can you tell me if the screw on the auto valve on the pump should be left lose? the manual states to losen it for commissioning but does not state whether to re tighten it or leave it lose

thanks

 

[bobw1956]

If you mean the chrome screw in the centre of the pump ? then it should be closed.

If you mean the cap on the AAV then it should be open

 

[russ2m]

just getting very frustrated now

had to wait till today to get some more fuses. made shure all the system is as it should be. valves etc

now however it is blowing the fuses within 3 second and the pump wont start (started last night and ran for about 1 min before blowing the fuse)

im going balder by the moment. thanks for all your help so far but still going mad

is there any way i can check the pump is free?

what else might be causing the fuse to blow? gas? or as its is the loft could there be a issue with cold?

thanks

 

[russ2m]

the unit has 2 2a quick blow fuses, one on the live and on the earth, these are internal. it is the 2a on the live which keeps blowing

 

[Agile]

That would usually be caused by a short to earth. Most often caused by the pump but it could be anything.

Dont be confused by the posting above saying a short is 450 ohms. That would not blow any fuse as the current would only be 1/2 A.

A short is going to be about 50 ohms or less. Unfortunately most boiler faults which are water related dont demonstrate a low resistance unless mains voltage is applied.

You can, if competent, power the pump seperately via a 3A fuse and see what happens.

Tony

 

[russ2m]

Thanks tony

powering the pump only, can do that, but can you confirm that this should be run without the boiler running or try to get the boiler to fire at the same time??

thanks

 

[Agile]

You only need to power the pump.

Once its powered, if it runs without blowing the fuse then you could try powering the boiler and see if that still blows its fuse.

I find that over 90% of fuse blows are caused by the pump. Most of the rest are water ingress related and the odd one the gas valve or fan.

Tony

 

[rojaca]

Tony . I was giving the approximate readings that are normally found on this appliance.