Glow worm Swift Flow 80 no hot water

[djheath]

I recently moved into a one bed flat which has quite an old (1993) Glow worm Swift flow 80 boiler. I noticed that the pressure gauge had gone down to 0.5 bar today when I came home. Since moving in in July the pressure has been at 0.7 bar and never dropped below this and I cant see any leaks anywhere. I filled it up to 0.7 bar on the filling loop.

When I went to turn the hot water tap on, water came out but the boiler didn't fire up.

If I leave the hot water tap running and tap the boiler on the side a click can be heard and the boiler fires. Sometimes it will stay lit (until the hot tap is turned off), or sometimes it will cycle on/off and click each time.

It has done this about three times since I moved in in July. Each time, I give the boiler a tap when it doesn't fire and it will work fine for ages as normal - although about twice now, after running the hot tap for a while, a strange gurgle noise is heard in the boiler, lots of water banging and the pressure will drop suddenly to 0 then return to normal again within a few seconds. After that the boiler usually refuses to fire up when the hot tap is turned on unless you wait for a few minutes. Pilot light remains on as normal.

However, at this moment no matter how much tapping I do the boiler wont stay alight. It clicks on when I tap it but will then click off again nearly staright away and not work!

I realise tapping a boiler is not the correct way to make it work and was going to get it serviced soon, but does anyone know what the problem could be?

Central heating is working fine.

Sorry for length of post, but does anyone have any ideas, or can recommend a freindly corgi plumber in the lightwater, camberley surrey area!

Thanks!

 

[Agile]

Pressurise the system to 1.5 bar for a start.

It sounds as if the DHW flow switch is sticking, quite a common problem.

Normally we would recommend Chris but he is languishing in a hospital somewhere in South Africa.

Tony

 

[djheath]

Ok thanks.

I set the pressure to 0.7 bar because thats what the manual said it should be set at.

I better get on the phone to someone then.

 

[Agile]

The low pressure switch is set at about 0.6 Bar so the working pressure has to be a lot higher than that. Its best set at 1.5 bar cold.

Tony

 

[djheath]

Update:

I put the pressure up to just over 1 bar and it still didn't work.

But then in the evening it did!

A corgi man came round today and had a look. After tapping the flow switch with his screw driver and the boiler fireing up then stopping then fireing, he said the flow switch was shot. Gah! £100 for two minutes diagnosis, and then he is coming back next week at another 2 hours labour plus £60 for the flow switch to be fitted. So nearly £300!

Im tempted to fit it myself! Im a pretty competent plumber and understand whats needed cos I cant do with the cost!


Thanks all for your help.

 

[Agile]

It sounds as if the DHW flow switch is sticking, quite a common problem.

Tony

Thats what I had already told you!

You seem to have chosen a very expensive CORGI !

We charge a fixed price diagnostic fee of £84 to visit but I told you free what the problem was likely to be.

But our fee includes fitting the new valve for which we only charge about £28 !

Its pretty simple to change so why not have a go. Just isolate mains water and electricity and TURN OFF THE PILOT TOO.

Tony

 

[djheath]

Sorry I wasn't dismissing your knowledge, but i still needed someone to come out and fix the problem, which I was hoping this company would do. Cost is always a bit of a shock never-the-less!!

I think I will have a go. I have the service manual with all the instructions on how to do it, and will obviously turn off everything before hand.

Cheers again.

 

[Agile]

Everyone should always enquire the charging basis before getting anyone to fix a boiler.

We charge a fixed price fee because as I usually diagnose a fault in a few minutes I would have to charge a very high hourly rate otherwise!

Also best to ensure its on a no-fix no-fee basis. Some of the call out companies still charge for attending without being able to find the fault !

Tony

 

[nickso]

dont the swiftflow's have the nut for the flowswitch inside the combustion chamber, meaning you have to remove the burner and pilot assy to get it out? pretty dodgy ground for a diyer

not worked on one of these piles for a while but i seem to remember i had to do that last time id changed one.