# Forum Home Renovation Heating & Cooling  Vulcan ducted heater problem

## HandyDaddy

Hi guys 
I'v got a Vulcan ducted heating system. When I tried to start it last winter and also this winter after being off all summer, it really does not want to start. After lots of messing about I eventually get it to go again and I'm convinced the problem is with the main gas valve. 
The system is a Modulating system and from what I can make out the main gas valve seems to sense differential air pressure from the combustion fan. It seems to me the combusion fan starts up and has to produce a pressure difference in the two sections of the combustion chamber either side of the combustion fan. I belive at startup this pressure difference in my system is borderline sufficient to turn on the gas valve. If I give the positive pressure pipe a quick squeeze when the ignitor is firing, the valve open and the system starts up.  
Additionally the system cuts out after trying to operate in Economy mode. In this more the system modulates the temperate (I assume by changing the fan speed and using the differential feedback to control the gas). In my opineon, this again points to a problem with the differential pressure control of the valve.  
Does anyone have experience with this type of heating system?  Is this a common problem? Can the valve be adjusted?

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## ozheat

4 & final try to post a reply....keeps locking up as I submit reply. 
few things to check.
The 2 pressure tubes aren't cracked.
The ends of the tubes aren't leaking at the pressure sensor.  It is easier just to pull the 2 tubes off and cut 10mm off each and reattach.
The tube sealing grommets aren't perished at the firewall.

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