Strange one with a J&S warm air unit.

[Mike Jackson]

Went to one in a static this morning. Apparently the first time it lights in the morning a flame shoots out of the bottom. After this first ignition it lights perfectly and burns beautifully. I stripped it down and checked the whole thing and couldn't find anything wrong. All I could find wrong with the whole installation was a cobweb partially blocking the air vent.

All I can think is that first thing in the morning the flue is cold and the slight blocked vent is not allowing quite enough pull when the heater first fires up. As soon as it is slightly warm there is sufficient pull in the flue.

Anyone got any different ideas? J&S reckoned it could have been a problem with the burner or injector but surely this would show up as a problem every time it fired.

 

[Kev the gas]

Low pressure in the morning when other appliances been used ? Low pressure on the site?

 

[Mike Jackson]

It's on it's own 4 pack. Pressure is fine.


Sent from my iPad using Tapatalk HD

 

[mountainman]

Low pressure from overnight cooling of the cylinders?

 

[stevetheplumber]

im not lpg or even sure which appliance your refering to but is it possible you have a very slight build up of gas overnight i had a leak on a pilot tube years ago caused a similar scenario try going before it lit and put a sniffer in?

 

[Pssst]

I'm with the OP's theory of low temperature flue stack due to overnight cooling.

It isnt uncommon to have a bit of an eye brow singer out the front of these when they fire up !

Have you checked that there is no main injector gas when in off/pilot only position due to wear on gas valve which may be pumping unburned gas into the heat exchanger and flue when not on,thus producing a whoomf when it fires?

Other than that,its fairly normal operation in my experience. The combustion chamber and profile is somewhat restrictive on many FWAs

 

[heliotrope]

I don't find it at all uncommon for the flame to lick out of the
combustion chamber when starting from cold.
It can be a bit disconcerting though if you have your face too
close when firing up, best to check flame picture when settled.

I find that if shooting out on regular basis then reduce burner
pressure to mid or low setting.
I've not singed any eyebrows yet but has made me jump a
couple of times.

 

[Pssst]

My most interesting experience with a FWA was with a mega imported semi commercial unit which was fitted in a rather palatial domestic premise. It was in a drive under garage,sharing space with a Bentley and a sports car of some description.

It had humidifiers and all sorts of extras on it.

The gas end of the operation...well it had a horizontal bar across the front onto which were fitted about eight(?) natural draught burners each about 18" long. There was a single pilot light in the middle and a horizontal cross lighter which ran the full width of the burner bar to light the main burners.

The gas control opened gradually on power up to ensure cross lighting.

I was there to service it and the punter pointed out that it was noisy..

After a singe'ing session i quickly noted that the ladder pilot had fractured part way down its length and on power on,half the burners to one side were not being supplied with a cross light !