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Low pressure warning light on Glow Worm Compact 100e?

Hello, I had a problem 2 years ago with my Glow worm Compact 100e, which would not switch from heating to hot water. I fixed the problem at that time by fitting a new neoprene type diaphram located behind the switch. There are two of these types of switches, one for the pressure differential micro switch and one for the domestic hot water micro switch, mounted on the hydroblock. I have in fact just replaced both again today. I flushed the system with a limescale / sludge dissolver for 4 or 5 days prior to this latest repair. I also previously then flushed the system with fresh water fully drained the system, re-filled, ran the boiler again for half an hour, and then drained it again.
I have one problem now though, which was evident before I drained the system in the first place, and that is the "Low Water Pressure Warning Light". It is glowing red. Do you have any idea what may be causing this please? The heating and hot water are both working ok, could it be the expansion vessel this time do you think? Or any other ideas / suggestions please. I got close to using a 4lb hammer on it two years ago, and putting the complete boiler on the MD of the manufacturers car bonnet as a mascot for him. ( Being a little older now, I don't think I could lift it anymore, and I seem to be a little more patient these days!).
Thank you for any possible replies posted to this fault. Chris Wiles

Chris Wiles
August 2007

Heating, Home Heating Systems Low Pressure Problem

Thank you hi-tech plumbing.
My mate at onlineboilerspares, graham has one, which I am about to go pick-up from Christchurch. They're about £25 normally. Yes i shall be a little less heavy handed fitting it. They are push fit with a circlip though, I reckon the plastic had gone a little brittle with the heat.
Thanks once again. I suppose you are off fishing this morning? I hope to go next week, see if I can catch myself a few turbot.
Byeeeee
chris.

Chris
September 2007

well sorry chris but im near southend in essex.
plus i don't have one on the van but never mind, don't know if you will get one tomorrow but try give plumbcentre a ring.
and make it early cause most will shut at midday tomorrow.

good luck when you get the new part and don't over tighten it when fitting.

catch ya soon.

hi-spec plumbing
August 2007

Hello Hi-Spec Plumbing,
You were dead right, it was full of muck. I used a syringe and hot water to flush it out, but, unfortunately, I heard a little crack when re-fitting it with the "O" ring in place and pushed the circlip back on. I though it was ok, but, when I started to pressurize the system I found I have a leak, dripping from that very part. Like you said, I should have got the part before I started buggering around with it! I'll have to wait until tomorrow now. The wifey will be most impressed with her "HOT" ha-ha bath tonight! I think I'll take her out and get her p*ssed, it might make life more bearable having to use a kettle for hot water later! I reckon that was the cause of the warning light though.
Thank you again for your input.
What part of the country are you based in? Coz if you are not too far away I'd get the part from you if you stocked it. I am in Spetisbury, near Blandford Dorset.
Thank you,
Best Wishes,
chris.

Chris
August 2007

>is there an easy way of flushing out the hydroblock

not really

have you tried removing the low pressure switch, i would say that is more faulty than muck in the system

>I suppose the muck is coming from the heat exchangers,

your heat exchangers are both ali shouldn't be a problem more like your rads as they are steel.

the filling loop idea is good but not very affective.

i would strip the low pressure switch out maybe a new one first
witch is just below gas valve.

hi-spec plumbing
August 2007

Hello Hi Spec,
is there an easy way of flushing out the hydroblock without dismantling the whole lot? I had thought about a power flusher, which a friend would lend me, but it seems a lot of work disconnecting the flow and return pipes to blast it through. On top of that, I had the boiler fitted at low level in a larder type kitchen cupboard which makes life awkward as it's in the corner of the kitchen on an outside wall. (Not much room for manoever, pins and needles in the knees and a short fuse, especially when the wife asks if she can have some hot water! because I can't reach her to give her a "fourpenny one" very easily, and she'd have buggered off back in the garden by the time I have got to my feet!) I suppose the muck is coming from the heat exchangers, (main and also plate to plate exchanger), as they are the only corrodible items in the system. I have closed off all the rads so that if I use the filling loop and open the main drainage point off the return pipe, hope fully it may blow the muck through like that? Anyhow, I'll try that, then pull the switch and see the muck.
bye for now,
chris

Chris Wiles
August 2007

thats all it can be now.

hi-spec plumbing
August 2007

Hello again and Thank You Hi Spec Plumbing.
I actually tried that this morning, but, has made no difference. I am about to drain the boiler a little, and take out the low warning pressure switch unit to see if there is any muck in there. I noticed that when I put the new diaphram in the pressure differential unit yesterday that there was a lot of fine grained rusty sh1t in the inside behind the diaphram, so it may be the same with the pressure unit.
I will let you know the result later on this afternoon.
Thank you once again for your help.
chris

Chris Wiles
August 2007

raise your pressure to about 1.2 / 1.5 bar.
0.7 bar is on it's lowest must boilers will only let the pressure drop to about 0.7 / 0.5 bar before they go into lockout mode because of low water content.
you should find your light will go out when you get up to about 1bar.

hi-spec plumbing
August 2007

Hello Hi Spec Plumbing,
Thank you for the reply, I re-filled the system as said in my note above, bled the system, and set the pressure (by the guage) at 0.7 bar, which is where I have it set from the original installation. When the system is fired up (including heating) it normally shows about 1 bar.
I forgot to put this detail in the note, sorry.
Regards, chris.

Chris Wiles
August 2007

what is the pressure gauge reading ?

hi-spec plumbing
August 2007