06-13-2015, 02:46 PM
Gang,
The 120V air compressor has been a mystery to me. I have followed several threads on gurus and that has helped me a lot, but today I learned more by taking it all apart and putting it back together. In the process, I found a hidden bug and now will be far less intimidated.
Before I tell you what I learned, I want to ask a question....
When the compressor shuts off due to it reaching the high threshold on the pressure switch...there is a solenoid controlled normally-open valve that is de-energized thus releasing pressure on the compressor. Why would we not use an integrated pressure switch that has unload built into it? For example...Square D pressure switch
The external solenoid based "unloader" works fine, but is expensive ...and... at least for me has been trouble prone. I have had two blow up from freezing water.
Here is what I learned today.
1. The hot leg to the compressor is switched via a relay that in turn is controlled by (at least). The switch on the galley control panel needs to be "on". Next, the pressure switch needs to be in "Auto" and the pressure in the system needs to be below the high cutoff set in the Square D pressure switch.
2. The "unloader" solenoid is wired in parallel with the hot wires of the compressor. It is normally open and is energized when the pump is running allowing pressure to go to tank. Once the compressor shuts off, it is de-energized and vents off any pressure so that the pump can easily start next time.
3. When I took the grey box that holds the AC relay apart, I found a loose connection and a seriously deteriorated spade connector. (Incoming 120V hot wire) I don't think it had started causing trouble, but would in the future.
4. I stole Tom's idea of putting a nice vibration mat under the compressor. Wow! what a difference. Now there is virtually no compressor noise inside the coach. Thanks Tom!
5. This falls under the duh category. But I will post here cause it was not obvious to me. When you turn off the compressor at the galley switch. All you have done is to remove 12V from the low voltage side of the 120V relay. In other words, there is still hot electricity inside the grey relay box. On my coach the breaker to turn off AC power to the entire compressor bay is located in the basement just in front of the water bay. If you work on your compressor, do yourself a favor and turn off the power.
6. This may be the most important lesson of the day....Before you start a project, read up on gurus and see if you can understand what folks that have walked the trail before you have encountered. I read about Tom's, Larry's, Richards, Chappel's, Marc's and others experiences. That got me ready to go. But in the middle of the project, I got frustrated cause something was not coming apart the way that I thought it should. That's when I got into a "Richard" state of mind and told myself....slow down....before you call Richard....think...what will he say? Funny thing is that I channeled my inner Richard and pushed through to a solution that was better and less work than what I was trying to do.
So thanks Gurus for breaking in the moccasins. They are so much more comfortable after you have walked the path in front of me!
Cheers,
bill
ps. If I have something wrong, don't hesitate to correct me!
The 120V air compressor has been a mystery to me. I have followed several threads on gurus and that has helped me a lot, but today I learned more by taking it all apart and putting it back together. In the process, I found a hidden bug and now will be far less intimidated.
Before I tell you what I learned, I want to ask a question....
When the compressor shuts off due to it reaching the high threshold on the pressure switch...there is a solenoid controlled normally-open valve that is de-energized thus releasing pressure on the compressor. Why would we not use an integrated pressure switch that has unload built into it? For example...Square D pressure switch
The external solenoid based "unloader" works fine, but is expensive ...and... at least for me has been trouble prone. I have had two blow up from freezing water.
Here is what I learned today.
1. The hot leg to the compressor is switched via a relay that in turn is controlled by (at least). The switch on the galley control panel needs to be "on". Next, the pressure switch needs to be in "Auto" and the pressure in the system needs to be below the high cutoff set in the Square D pressure switch.
2. The "unloader" solenoid is wired in parallel with the hot wires of the compressor. It is normally open and is energized when the pump is running allowing pressure to go to tank. Once the compressor shuts off, it is de-energized and vents off any pressure so that the pump can easily start next time.
3. When I took the grey box that holds the AC relay apart, I found a loose connection and a seriously deteriorated spade connector. (Incoming 120V hot wire) I don't think it had started causing trouble, but would in the future.
4. I stole Tom's idea of putting a nice vibration mat under the compressor. Wow! what a difference. Now there is virtually no compressor noise inside the coach. Thanks Tom!
5. This falls under the duh category. But I will post here cause it was not obvious to me. When you turn off the compressor at the galley switch. All you have done is to remove 12V from the low voltage side of the 120V relay. In other words, there is still hot electricity inside the grey relay box. On my coach the breaker to turn off AC power to the entire compressor bay is located in the basement just in front of the water bay. If you work on your compressor, do yourself a favor and turn off the power.
6. This may be the most important lesson of the day....Before you start a project, read up on gurus and see if you can understand what folks that have walked the trail before you have encountered. I read about Tom's, Larry's, Richards, Chappel's, Marc's and others experiences. That got me ready to go. But in the middle of the project, I got frustrated cause something was not coming apart the way that I thought it should. That's when I got into a "Richard" state of mind and told myself....slow down....before you call Richard....think...what will he say? Funny thing is that I channeled my inner Richard and pushed through to a solution that was better and less work than what I was trying to do.
So thanks Gurus for breaking in the moccasins. They are so much more comfortable after you have walked the path in front of me!
Cheers,
bill
ps. If I have something wrong, don't hesitate to correct me!
Bill Johnson
Birmingham, Alabama
