|01-06-2013, 01:14 PM||#17|
Joined: Sep 2010
Location: frozen north
Can you see the pilot flame ? it should be bright blue and fully engulf the tip of the thermocouple , if there is one .
Does your power vented water heater have a flame sensor , in addition to the thermocouple ?
If you inspect the connections between the burner and pilot assembly ( hidden in the bottom of the unit ) and the gas valve , you may see a thin wire , in addition to the pilot line ( 1/4 " dia aluminum tube ) , the main gas line to burner ( 1/2" dia aluminum tube ) , and the thermocouple ( 1/8 " dia copper solid wire ).
If so , the wire is for a flame sensor , which must be cleaned occasionally , by gently sanding the probe , located at the burner .Note - sanding a thermocouple does no good , they're cheap and easy to replace . A thermocouple creates electricity , approx 250 millivolts , by being engulfed in the pilot flame . A flame sensor conducts electricity when engulfed in flame , thereby proving that the flame is lit.
To clean the flame sensor , and/or replace the thermocouple ( might as well while you're in there ):
1) shut off gas to appliance . We don't want to read about you in the paper tomorrow .
2) disconnect all outputs from bottom of gas valve ( flare fitting for main and pilot lines , thermocouple , sensor wire , etc.)
3) remove burner from bottom of water heater
4) clean sensor , replace thermocouple
5)re-assembly is reverse- ensure burner is properly placed - scope it out with a flashlight as you reinsert burner , there's probably tabs to locate it.
6) turn on gas , relight burner and test all joints with soapy liquid for leaks .
As a licenced gas fitter , this would take me about 1/2 hour to do , and I'd charge $80.00 plus travel
Naturally , you accept full responsibility for your actions , if unsure , call a qualified technician .
|01-06-2013, 01:44 PM||#18|
Joined: Sep 2010
Beware the intake air lockout when messing with the burner. If your heater is new enough, it'll have a one-time-only safety on the intake air that once tripped, requires throwing away the whole heater. What trips it is a blowout from unburned gas igniting. Doesn't take much. BTDT.
|01-06-2013, 02:00 PM||#19|
Joined: Aug 2008
Location: N.W. Arkansas
ok EDIT - shit sorry, im thinking gas furnace not water heater, never mind!~
is it lighting the burner at all? as in, does it light and then go out?
or just it just continually try to cycle without the gas valve ever opening? ( if there is a pilot light, it will light the gas burner when 24Vac is put to the gas valve)
it is the control modules job, to open the gas valve for usually 4 seconds, then wait for the flame sensor
flames sensed, gas valve stays open until thermostat is satisfied.
no flame sensed, gas valve closed, and cycle starts over
usually 3 cycles ( attempts to light) , with a 30-40 seconds purge ( fan on) in between until a lockout occurs.
after lockout, you will have to remove power from the control board for 45 seconds or so to reset it.
"A little inaccuracy sometimes saves a ton of explanation."
- H. H. Munro (Saki) (1870-1916)
mouthfulloflake screwed with this post 01-06-2013 at 02:11 PM
|01-06-2013, 02:03 PM||#20|
Joined: Aug 2005
Location: Central Ohio
Sure sounds like a pressure switch. I had something very similar with my furnace.
You need to determine the logic of the startup cycle and troubleshoot each component in order.
You can determine if the pressure switch is working by checking with an ohm meter.
My guess is that when the power vent kicks on, the pressure switch should close, and then gas valve open, and gas flows. Then a flame sensor would check to see if the unit lights within a few seconds, and if not, it will shut down and try to recycle.
If the pressure switch closes when the power vent kicks on, and the gas valve doesn't open, you've got a different problem.
Unfortunately, testing the control panel is difficult, if not impossible, other than swapping one out.
|01-06-2013, 02:14 PM||#21|
Joined: Sep 2003
Location: Mt. Vernon, Illinois
As a lifelong state licensed plumber that spent his whole life installing and repairing steam and hot water systems I can tell you professionally that a water heater is the very most in-efficient way to heat a building using your radiant heating system. The efficiency rating is a small percent of what a boiler is made for that purpose. But water heaters are cheaper than boilers------just so you know.
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|01-07-2013, 10:06 AM||#22|
Joined: Jan 2011
Thanks for all these ideas. The annoying thing is if I go downstairs right now and turn on power to the unit it will start right up and run fine until everything is up to temp. It's only the next time it tries to turn on that it wont fire up. It just tries over and over.
Bigdog, I know that this water heater isn't as efficient as a real boiler. I'm just heating a 450 sf basement shop to about 50 degrees. If I have a big project going I might turn it up to 55 for a couple of days. I just didn't think I needed to spend 3 or 4 thousand dollars for a real boiler for this application. The whole thing has worked fine for over a decade.
So what I've been doing the last few weeks is to just turn it on and let the floor/room heat up then turn it off when I hear it failing to light. I will find time soon to go over the manual.
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