Central Heating - 2 issues

[andrewprouse]

Hi there,

I'd like to start by saying that I love this forum and it has proved invaluable to me since moving into my new house. I have been looking over this forum and others for months now for answers but I still have the same 2 very annoying problems.

Since moving into my new house (Feb 2010) we have had central heating problems from day 1. There has always been air in the system and there has always been an issue with fuses blowing.

Issue 1 - Fuse Blowing

Bit by bit I have replaced nearly all components of my fully pumped open vented system to try to get to the bottom of the FUSE BLOWING issue. I have replaced the motorised valve, the pump, cylinder and room stat, wiring centre and programmer (now all Honeywell). I have also re-done all of the wiring.

The issue I have is that RANDOMLY the 2amp fuse in the honeywell wiring centre blows. Sometimes this fuse can last a month, other times it blows every night! (The fuse nearly always blows at night). I initially put it down to the programmer temporarily shorting between 'switches', but having gone through 3 programmers now I'm kinda guessing that it's something else causing the issue.

It's really wierd and really annoying because I can simulate the night time switching pattern during the day (by re programming the programmer) and the fuse won't blow.

If it was a wiring issue (a dead short) then the fuse would blow everytime 'that something' happens, but sometimes the fuse can last weeks. Really wierd!

Issue 2 - Air in Rads

My second issue is with air in the rads. Air collects in just 2 rads upstairs (a towel rail and a small single panel rad), but I'm talking about LOADS of air! Every day I have to bleed the rads and before I do I can feel (using my hand to sense the temp change) the level of the water within the rad. Within a 24hr period the tower rail becomes 75% full of air and the single panel rad becomes 90% full of air. This must equate to someting like 12-15pints of water being displaced (in a 24hr period).

I have power flused the system (1 rad at a time) and have added inhibitor upon refilling. I initially thought that air was being sucked in through the vent pipe so I raised the water level in the header tank by as much as I could (1 inch) but this hasn't helped.

Is there a way of telling where else air may be getting sucked in?


Any suggestions to either of my problems would be very welcome.

Cheers, Andy

 

[D_Hailsham]

Issue 1 - Fuse Blowing

The issue I have is that RANDOMLY the 2amp fuse in the Honeywell wiring centre blows. Sometimes this fuse can last a month, other times it blows every night! (The fuse nearly always blows at night). I initially put it down to the programmer temporarily shorting between 'switches', but having gone through 3 programmers now I'm kinda guessing that it's something else causing the issue.

Not really a solution, but it seems strange that Honeywell use 2A fuses while most boiler manufacturers etc specify a 3A fuse for the fused spur feeding the system.

Is this a year round problem, or is it confined to a particular time of the year?

Which motorized valve(s) do you have?

Which boiler do you have - make and exact model?

Issue 2 - Air in Rads

I initially thought that air was being sucked in through the vent pipe so I raised the water level in the header tank by as much as I could (1 inch) but this hasn't helped.

The way to check if air is being sucked in is to fill a container,e.g a jug, with water and hold it so the vent pipe is dipping in the water. If there is a problem, the water will be sucked out of the jug.

Raising the water level won't help; you need to reset it to the correct level, here's how:

1. Let the system cool right down.
2. Clean out all the sludge in the tank, so it won't enter the system when you do the next bit. (Use a bucket, trowel and old rags etc)
4. Open a drain tap (on the ground floor near a rad - looks like a push on hose connection) and let water out until the ball valve opens to let the water in.
5. Make a mark to show the water level when the ball valve opens.
6. Close the drain tap.
7. If the mark is less than 2cm from the top of the bottom outlet, bend the ball valve arm up; if more than 5cm from top of outlet, bend the arm of the ball valve down.
Repeat 4 to 7 until the level is between 2cm and 5cm from the top of the outlet.

Bleeding must be done with the system cold. Bleed downstairs rads first.

Have you bled the pump? Remove the large screw in the centre of the data plate. (Hold a rag underneath to catch the inevitable drips of water.)

Is there an automatic air valve on the system?

 

[rego]

do you have a back boiler
fuse blowing could be caused by cable into boiler heat damaged
seen it happen before

 

[spraggo]

Hi there,

Issue 1 - Fuse Blowing

Cheers, Andy

(1) Try fitting a 2 amp anti surge or a 3 amp fuse

(2) The inverted U bend on the expansion pipe going into the tank should be 450mm above the water level to prevent pumping over.