Glowworm Ultracom 18sxi failed to fire up.....

[mjnelson]

Hi there,

I am perplexed. If anyone has any ideas on the following, I'd really appreciate it:

I have a Glowworm Ultracom 18sxi high-efficiency condenser boiler located in my garage, and for 2 years it has worked fine. However, twice now (before Christmas and this morning!) it has failed to fire up in the morning. Both times, it has been a very cold night (frosty/ice outside) and when I have looked in my airing cupboard to see what the system pressure is, it has read virtually zero. So, I have re-pressurised and taken the gauge to approx one bar......and the boiler then fires up and the house gets nice and toasty.

BUT.....when I checked the gauge an hour later, it was reading approx 3 bar and when I looked outside the pressure relief pipe was spluttering out some water! Normally, when cold the gauge reads approx one bar and when hot approx 2 bar.

So.....can anyone suggest why the boiler failed to start on an icy morning, yet adding water (increasing pressure) caused it to fire up, yet the pressure then rocketed?

My only thought is: the condensor drain pipe might have frozen, causing boiler (as per design) to fail, but don't see why gauge in house would read zero, nor why adding "fresh" water would solve this (but it does kinda explain why the pressure went up to 3 bar, if really it was already at one bar and then I increased it by one bar.....I'm clutching at straws here!!)

Any ideas?! Thanks for your time,

Matt

 

[Agile]

You should spend a little time reading the topic at the top called FAQ.

Its either a leaking filling valve or a non functioning EXV.

Tony

 

[mjnelson]

Thanks for the quick reply, Tony.

Sorry, I'd skimmed through the FAQs but had not associated my symptoms with those that you have highlighted for me.....I think I was focused on the trees and not seeing the wood. My fault.

So.....having re-read the Expansion Vessel bit (FAQ 31) it does sound a candidate. D'ya reckon this is the kinda thing they (GlowWorm) would fix/replace during an annual service / breakdown cover? Just wondered.....

Again, thanks for your time and knowledge

Matt

 

[gas4you]

They should do.

 

[mjnelson]

Good stuff, that's one less thing to worry about at the moment then.

However, I am still confused about "stuff"..... Basically, the pressures seem ok again now - hovering around 1bar when cold and towards 2bar when hot. So, is there something specific about a very cold night (and the boiler has been off for several hours - late evening 'til 6am'ish) that causes the Expansion Vessel to "misbehave" ? Is it because the Expansion Vessel is (possibly) under-inflated and the really cold air in the garage causes the membrane to contract even further, or.............. ?

Sorry to ask more questions, I'm just kinda interested in the hows/whats/etc.

Thanks for tolerating me,

Matt

 

[mjnelson]

.....Hi, back again!

Ok, So I've had GlowWorm out and they replaced a faulty ignition unit and a couple of rubber gaskets around the burner (that had perished - apparently, if left it could have ended in a fire - nice).

Whilst they were out they checked and re-checked the PRV and the Expansion Vessel and said that everything was fine. This was approx. a month ago.

However, last night it was well below freezing and this morning.....no heating! I went out to the garage and the boiler was flashing 0.6bar - but last night it was 0.8bar (lower than the ideal 1bar I know but.....) - - - so I went back indoors and added some water - taking it to about 1.2bar and it fired up. When I checked the PRV outlet, it looked damp......so can anybody confirm whether this could be an issue with the Water Pressure Sensor? My theory - when it's really cold, the sensor goes apesh!t and reports too high pressure, the PRV releases some (the last month it has been dry around the outlet - so it's not a steady leak) then the sensor detects pressure too low and fails to fire. All guess work, of course. I'd just like some suggestions before we get GlowWorm back out. If it helps, the analogue pressure gauge in the airing cupboard (indoors, upstairs) reads lower than the boiler's digital display.

Any ideas? Thanks in advance.....

Matt

 

[Agile]

It sounds as if you dont have a frost stat to bring the boiler on when the temperature in the garage falls below 5 C.

I would have expected your boiler had one built in but perhaps its has been turned off or is not functioning?

Tony

 

[mjnelson]

Thanks for the reply, Tony.

My boiler supposedly has Frost Protection - "The boiler has a built-in frost protection programme.....this device operates the burner and system pump when the temp inside the boiler falls to 3degrees....."

As it's a built-in "programme" - how on earth do I test, "fix" or replace it?!

The whole thing is confusing me, to be honest.

PS Also, and I doubt it makes any difference, the title of my thread is slightly incorrect. My boiler is just an 18sxi - not an Ultracom 18sxi.

 

[mjnelson]

.....just thinking, could it be the expansion vessel hose is blocked? Would this explain the difference in pressure (boiler display and analogue gauge in airing cupboard) and would this cause the symptoms described?

It would also explain why the prv and expansion vessel appeared fine to the engineer.....

Any thoughts?

Matt