Original message
| realjd
 |  "Amer Std and Carrier rooftops not heating"
, posted Thu 1 Jan 19:10  
All rooftop units gas heat,Amer Std with neg pressure regulators and Carrier units try to fire, ignitors ok,blower on,limits ok,tries 3 times but fails to fire on all units. Help!
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Replies:
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| Freezone12
| "Re(1):Amer Std and Carrier rooftops not heati" , posted Fri 19 Nov 17:43
If you only have 2" of gas coming into the valve, I suspect that is your problem. It would also help explain the other heating units not working as well. Most, if not all heating appliances require a minimum 3.5" wc to operate, if we are talking natural gas. (I believe propane is 10" wc). The negative readings you are refering to are taken after the gas valve, but you'll still need the 3.5" supply to the valve.
If it don't fit force it.
If it breaks it needed to be replaced anyways.
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| realjd
| "Re(1):Amer Std and Carrier rooftops not heati" , posted Thu 1 Jan 20:26
Will try and check main gas pressure. Checked pressures at gas valve on couple of units,had somewhere like 1/2 inch at valve inlet and -2.0 to -2.5 at outlet. (Is that too much?) Units require -.2 inches at outlet. I am told all units worked properly last year, I doubt that.
Will have to shut main,and put reducer fittings to read pressure.
2 in. gas main feeding approx. 20 units.
Also, in building there are several dayton gas heaters,have lit pilots on them,fan comes on,voltage to gas valve,but none fire up. These are on different gas line.
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| | xenos
Webmaster 
| "Re(2):Amer Std and Carrier rooftops not heati" , posted Thu 1 Jan 20:50
The only reason I am thinking it’s gas as I am sure you are is that there are several unit’s why several the odds are not there all though it’s possible it’s different problems. Now half an inch is high considering it should only be a quarter (7inches). However most regulators are rated to half an inch inlet so the outlet should be good ( maybe). The carrier unit do you have a model number?
Just for reference -2.5 is less than -.2 if your running at -2.5 and are looking for -.2 you will have to increase the pressure. However I have always like to verify the pressure before the valve and after the reg ( at 3.5) as the air pressure can effect the gas reading.
Now we are talking about Nat gas Correct. Or is this propane. I have ran into this many times with propane what the pre heaters broke down and the liquid wouldn't vaporize in cold weather. This can happen since the demand is so large on the tanks that the pressure drops too fast and the tank can’t absorb heat fast enough.
Xenos.
The best way to escape a problem is to solve it.
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| xenos
Webmaster
| "Re(1):Amer Std and Carrier rooftops not heati" , posted Thu 1 Jan 19:22
I would be checking the main gas pressure and if propane make sure the pre heaters are running out at the tanks.
Xenos.
The best way to escape a problem is to solve it.
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| | realjd
| "Re(2):Amer Std and Carrier rooftops not heati" , posted Thu 8 Jan 01:48:
Yea, I agree with you that it must be gas problem with all the units. I asked them where the main reg. was located and there was a branch feeding the line to the roof units,someone had shutoff the valves feeding the units. Problem solved.
thanks
[this message was edited by realjd on Thu 8 Jan 01:51] |
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