Question To you HVAC folks



Ok. You could take some clear plastic tubing and build a manometer. Or if push came to shove, put in a Schrader valve and use a tire gauge to get a rough reading. But the gas pressure probably isn't the problem since it is a preexisting system, unless the pressure regulator for the gas has gone bad. Another things to consider, since we can't see the setup, is the environment. Is it in a humid or dusty area? Humidity can cause spade connections to corrode, and if it is bad it can cause the burner to rust inside and the rust can block the gas flow.. Dust can get into burners and block the gas flow. It is a heater system to remove water from oil. Is the water vented outside or inside where the unit is? Is there any corrosive chemical used in the area? If so, connections may be corroding. Take a good look at the inside of the unit to see if it looks like water has been condensing in it. If so, the controller may have simply gone bad due to the water. Others have mentioned the flame sensor may be dirty. That could easily be the case especially if the flames have any yellow in them, the flames should burn blue. Yellow means incomplete combustion and sooting. Check the inside of the combustion chamber for sooting. Remove the flame sensor and wipe the sensor with a clean paper towel.. A little discoloration on the towel is normal but there shouldn't be black soot or at least very little. If cleaning the sensor solves the problem, inspect the inside of the burner to insure it is not blocked with foreign matter(dust, insect, rust,etc.), adjust the air inlet(s) on the burner(s) to eliminate any yellow flame. If the blower supplies the air for the burner, adjust the blower to eliminate any yellow flame. If the system is a very old one consider the gas line for a moment. Does it have a drip leg. If it has a drip leg at the unit, you might turn off the gas and remove the drip leg to insure that it isn't full. If for some reason oil or water has filled the drip leg it could be causing the flame to burn yellow and soot. But honestly, I've never seen a drip leg get that full. If it doesn't have a drip leg you might install one to prevent any oil or moisture from making it to the gas valve and burner. I take it the lines are iron pipe since you said they were 1". But since the unit has been there for some time any oil in the pipes that could migrate to the unit has probably already done so.
Loyd
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I ran into a simlar problem on our furnace. A friend suggested that I check the "flame sensor". In my unit it was a stainless steel rod that stuck into the flame. I removed it, it is on a little bracket, and cleaned it with denatured alcohol and when I reinstalled it the furnace worked fine. My friend said that after years of being stuck into a flame, the sensors get coated with a fine film of ash that insulates it. All I know is that a good cleaning solved my problems. Terry
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wrote:

Well, you've gotten some good advice so far. Gunner.
I read thru the responses to your posts. Seems as if folks have covered all the probable things.
So I doubt I can offer much of value.
However, a couple points stick out in my mind and cause me to go Hmmmm.
You say entire blower unit was removed and sent off for a bench test and it supposedly worked there, on their test bench. AND You say it doesn't work on site. AND You describe the sequence of operation of the controller as being somewhat flakey on site. Sometimes multiple cycling of the solenoid, sometimes not. Sometimes does the 3 retries, sometimes not.
The above bothers me. Makes me sorta curious.
The thing about those controllers is that internally, they have digital circuitry. All digital circuits absolutely HATE differences in ground potential, any differences, between this point and that. Some are a little more tolerant than others, some less.
In my experience, that particular series of Honeywell controllers is one of the top haters of any differences in ground potential anywhere within it's internals, or anything connected to it.
Differences in ground potential which are minute, which would make no difference in electrical or electronic controls systems, can confuse and confound that line of Honeywell controllers.
So I wonder to self.
Hmmm. What is different between what you're calling the "blower assembly", which worked on a test bench. And what you're working with when you have everything put together on site, and now things aren't working.
Did that "blower assembly" (I have no clear picture of exactly, precisely all the components you mean when you say that), as tested on the test bench include the very same transformer? The same solenoid valve? The same gas valve? Etc.
Do you see what I'm getting at? What's different that's connected to that controller now, from what was connected to it when it was bench tested.
First thing which jumps into my mind is that often when somebody says "blower assembly" ... that doesn't include the burner itself. May, or may not. ---- ALL---- grounds that system, anywhere in it, is supposed to have, MUST be solidly connected to that burner. You don't want even 2 ohms of difference between this leg of ground and that. Check the schematic. See all the points to be ground. Make absolutely sure that when testing from this point in ground to another, that your meter is as flatlined as possible. Personally, I'd make sure I wasn't measuring anything over one ohm anywhere. Less if I can make it happen.
Next, I'd check connection from burner to cabinet. Now, sometimes folks rely on simple metal to metal contact between the pipes and other metal parts to establish that electrical connection to ground. And there is no separate ground wire bolted to burner, then bolted to the cabinet. This can work fine on a brand new unit.
Can suck, and drive yah nuts trying to figure out the problem on an older unit. With age, joints and connections corrode. Resistance increases. Or ground path included a section of pipe, and somebody took it apart, and upon reassembly used some sealant on threads. And what used to be a good ground path is now not such a good one.
I'd make sure. I'd add a damned good ground wire from burner to cabinet if there was not one. If there is, I'd investigate. Conductor intact? Both connections good, and solid and clean? Etc.
I'd then double check. Power shut down. Do I measure zero ohms, or damned close to it, from grounded leg of transformer to cabinet? From gas valve grounded terminal to cabinet? Ground terminal(s) on controller to cabinet? Ground of ignitor to cabinet? Etc.
That everything looks okay, doesn't hack it. Measure, verify. No more than 1 ohm, preferrably less. And I'd personally go for less.
After verifying that. My next step would be to verify, beyond any doubt, that the cabinet is grounded to EARTH ground.
One problem when dealing with digital circuits in particular arises here. In many installations, particularly older installations, cabinet ground was made by the electrician with him relying on a ground path running thru the conduit (if there is some) itself. In other words, he used the metal pipe as a ground path. This kinda, sorta works. Most times, most applications, works fine.
At first.
Problem is, the passage of time. All those conduit fittings that used to be tight, clean, nice metal to metal contact, after the passage of time often become not so tight, not so clean, etc. And if cabinet itself was grounded to earth ground via a path thru the conduit material itself, over the passge of years you might find there is significant resistance now built up (and thus potential, voltage, differences) between the cabinet and the actual earth ground of the building. As measured at the electrical service entry.
Not a good thing. Couple volts aren't gonna hurt or even be noticeable to regular electrical devices. Some types of digital devices, and that Honeywell controller is one of em, aren't gonna like it much.
BTW, do NOT consider a connection to AC common the same as a connection to ground. Period. I don't care that back at the breaker panel common may be hooked to the same ground bar as the ground wires. Do NOT consider a common wire as ground. Ground is ground. Common in normal operation carries current. Yah don't want the ground for that controller hooked to anything carrying current. Will confuse the devil out of it.
The above ground related things, I'd be inclined to check, and double check first.
Then I'd check whatever else is hooked to that controller one way or another, that did not accompany it to the shop for bench test. What else, that wasn't attached to it during bench test, might be shorting to ground, drawing too much current, etc.
Sometimes a transformer will seem fine. Measure output voltage, she looks good. Hook her up to something that's drawing too much amperage, i.e. a relay or solenoid which does a big spike draw upon energizing, voltage droops. Sometimes very quickly then comes back to normal because relay coil dropped out and field collapsed. And what you hear is chatter. Often yah can't see that rapid fluctuation on many meters. But yah can usually hear it. Problem might be relay or solenoid coil is drawing more than it used to, particularly on energizing and making something move (inrush current), or windings are starting to fail and after a moment get too hot. Or sometimes it's the transformer. Age. Might say 40 watts on the label, but she can't handle half that any more. And particularly on inrush current draw, she starts putting out erratic, drooping voltage. Digital circuitry does not like this sort of thing.
Just some thoughts.
Best of luck.
Bob
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