AC Pressure Transducers to N2K?

[nautibake]

AC is working well for the most part, but occasionally firing the HPF and auto shutdown. I would like to monitor the 5 condensers pressure from the various N2K displays on board.I have the Maretron FPM100 module and 5 pressure transducers. These have 1/4” NPT male (photo attached). Can someone please advise (this eldumbo) where to attach the transducers to the condensors? I know I will need an adaptor. Any thoughts greatly appreciated.

 

[KPTIM]

Hi Jerry,
Would you be interested in pressure sensors that would let you monitor the pressures of your AC system from your smart phone or device over Blue Tooth?

I work directly with a company that has a Blue Tooth based sensor system, one for the high and one for the low pressure port. It will screw right onto the current service port of your condenser / compressor with no adapters. The one in your photo looks like it is 1/8" npt and you will need a 1/8" npt to SAE 7/16-20 45 deg flare adapter..

they have a pretty cool app that talks to them.

If you are interested I can send you a photo of a set on a Cruisair unit and a link to the info?

 

[nautibake]

Thanks Tim,
I already have a remote access gateway to the entire N2K network with the Maretron IPG100. I just need to get the transducers connected and then plug the FPM100 (fluid pressure) module plugged in to the network. The documentation that came with the transducers says “1/4-18 NPT Male”.

Sorry I am clueless on the AC, but I believe the High Pressure side is the red, but want to be sure I connect the transducer to the right place. Here is a close up in case it helps. Are either of the two red valve caps where I should connect the transducer?

 

[nautibake]

Also an option on the top of the newer units might be better.

 

[Pascal]

I m not sure there are any benefits in constantly monitoring gas pressure. What would be more useful I think would be raw water temperature sensor at the discharge side. That would alert you to restricted flow before issues get worst

 

[Reefgeorge]

Blue usually means low/suction side and red usually means high/liquid side. The high side should have a smaller diameter line heading to the evaporator and be warmer and the low side should be a larger diameter pipe returning and be cooler. The ports that you show are the service and charging ports, not the best place for transducers. Elsewhere should be ports where the existing high and low side pressure sensors are attached which usually have schrader valves allowing "hot swapping" of sensors. Always crack those slowly in case the schrader core is leaking, especially on the high side where a release can be catastrophic. If you do decide to attach to the service ports, be sure that you understand the fully back seated and not fully back seated positions before removing those caps because again, a mistake here can be dangerous. There are NO schraders on the normal service ports, so if you remove the caps with the wrong valve position you will be venting the system.

George

 

[nautibake]

I m not sure there are any benefits in constantly monitoring gas pressure. What would be more useful I think would be raw water temperature sensor at the discharge side. That would alert you to restricted flow before issues get worst

Thanks Pascal. Maybe so, but I have gone a little bizerk with sensors and already had the Maretron module so what the heck. The HP fail has happened the past 3 times we have gone out with guests on board, so I want to be able monitor from the helm. Yes, probably overkill, but I like monitoring the data. Great idea on the raw water exit temp, I hadn’t thought of that. Will add it to the list. I have raw water flow sensors on the GenSet and both Seakeepers that have been a big improvement. Maybe the exit temp on the AC pump is better than just another flow meter.

As an aside, I also have timers and counters connected to each bilge pump available on the N2K and it provided an early warning of a raw water pump failure that was pumping a deluge into the generator room last year on the way to Key West, so I am rationalizing all the other things I can monitor, even if not pragmatic!

Blue usually means low/suction side and red usually means high/liquid side. The high side should have a smaller diameter line heading to the evaporator and be warmer and the low side should be a larger diameter pipe returning and be cooler. The ports that you show are the service and charging ports, not the best place for transducers. Elsewhere should be ports where the existing high and low side pressure sensors are attached which usually have schrader valves allowing "hot swapping" of sensors. Always crack those slowly in case the schrader core is leaking, especially on the high side where a release can be catastrophic. If you do decide to attach to the service ports, be sure that you understand the fully back seated and not fully back seated positions before removing those caps because again, a mistake here can be dangerous. There are NO schraders on the normal service ports, so if you remove the caps with the wrong valve position you will be venting the system.

George

Great info Reefgeorge, much appreciated. There are additional ports on top of the 3 of the newer units that look like a better option. After reading your post I may just get the AC guy back on board, I can’t get the adapters until Monday so I have some time to ponder it. Looks like a mistake is not necessarily a trivial thing... Thanks again...

 

[krush]

You are just asking for leaks of refrigerant by adding the sensors on this system. And if you are using r22, very expensive leaks.

 

[MVCaprice]

I m not sure there are any benefits in constantly monitoring gas pressure. What would be more useful I think would be raw water temperature sensor at the discharge side. That would alert you to restricted flow before issues get worst

Yep. You could use http://www.yachtd.com/products/sensors.html the YDTC-13 for this and they are less than 100$ a pop. I just threw one in to monitor engine room temp and its working pretty good.

 

[nautibake]

You are just asking for leaks of refrigerant by adding the sensors on this system. And if you are using r22, very expensive leaks.

After I read this link back in August, I was well, krushed. I had already bought 5 pressure transducers and the Maretron FPM100 module so I could monitor the AC pressure while we are underway. That is when I seem to have the most problems with getting the HP error and auto-shut down (not popular with the admiral or passengers). Anyway, I stuck it all in a box and stashed it down in the generator room, but keep thinking about the pros vs the cons.


krush - you raise such an interesting point about asking for leaks by adding sensors. At the same time, I've hacked into dozens of other lines and wires to install flow sensors, switch sensors, run sensors, timers, etc etc. So - I get the impression that refrigerant and these types of sensors add an addition level of leakage risk, is that right? Thanks, just want to confirm before I try to get rid of a few more things that I may have bought at retail and will sell at wholesale or less

 

[racclarkson@gmail.com]

After I read this link back in August, I was well, krushed. I had already bought 5 pressure transducers and the Maretron FPM100 module so I could monitor the AC pressure while we are underway. That is when I seem to have the most problems with getting the HP error and auto-shut down (not popular with the admiral or passengers). Anyway, I stuck it all in a box and stashed it down in the generator room, but keep thinking about the pros vs the cons.krush - you raise such an interesting point about asking for leaks by adding sensors. At the same time, I've hacked into dozens of other lines and wires to install flow sensors, switch sensors, run sensors, timers, etc etc. So - I get the impression that refrigerant and these types of sensors add an addition level of leakage risk, is that right? Thanks, just want to confirm before I try to get rid of a few more things that I may have bought at retail and will sell at wholesale or less

I think you just diagnosed your problem. If the cut-outs are more frequent underway you are possibly having a raw water pickup problem similar to head issues mentioned by other posters from time to time. FWIW, I just re-plumbed a well functioning four unit AC raw water cooling line by straightening it out and, thereby, shortening it by 4’ of hose. My discharge temp under identical conditions reduced in temp by 4 degrees. That differential between seawater intake and discharge was about 12% cooler. Seemed a worthy project.

 

[Reefgeorge]

I'm an engineer and love techie stuff but as I get older I increasingly look for connecting dots with small straight lines. I use this all the time - attach analog gauges, take a cheap camcorder and secure it aimed at the gauges and produce the fault. Go back and watch the time stamp along with the gauge readings. If Robert is correct then the high side pressure skyrockets as you get underway and the system shuts down. Easy peasy. No Nobel Peace prize but the Admiral goes to happy wife status faster and you still look like a genius. And you didn't even have to watch any you tube videos.

George

 

[racclarkson@gmail.com]

Made this up to get rid of 4’ of raw water hose that was S-looped and often in the way. Mates up to pump intake.

 

[oscarvan]

There is something in the back of my head that gets a little nervous when I see PVC open to the outside below the water line......

 

[racclarkson@gmail.com]

Me too. That's thick wall copper and bronze.

 

[nautibake]

Made this up to get rid of 4’ of raw water hose that was S-looped and often in the way. Mates up to pump intake.

Interesting, and impressive decrease. I wonder if the formula (from your results) hold up consistently: 1 degree reduction per 1' of hose eliminated or if there are other variables? I will have to take another look at the plumbing to see if there are opportunities to eliminate any excess...

 

[nautibake]

I'm an engineer and love techie stuff but as I get older I increasingly look for connecting dots with small straight lines. I use this all the time - attach analog gauges, take a cheap camcorder and secure it aimed at the gauges and produce the fault. Go back and watch the time stamp along with the gauge readings. If Robert is correct then the high side pressure skyrockets as you get underway and the system shuts down. Easy peasy. No Nobel Peace prize but the Admiral goes to happy wife status faster and you still look like a genius. And you didn't even have to watch any you tube videos.

George

Thanks Reefgeorge, great point. I need to start abiding by the less-is-more philosophy. I might even be able to use the new security cam in the engine room to record the pressure readings (on 2 TB video server). Oops there I go again...

 

[nautibake]

Yep. You could use http://www.yachtd.com/products/sensors.html the YDTC-13 for this and they are less than 100$ a pop. I just threw one in to monitor engine room temp and its working pretty good.

I think this is the route I'm going to go, but with Maretron TMP100. I can hook up the raw water discharge and add 5 more sensors for other temps to the same unit.

I'll likely be posting a Maretron FPM100 and 5 pressure transducers for sale soon. Sigh...

 

[racclarkson@gmail.com]

Interesting, and impressive decrease. I wonder if the formula (from your results) hold up consistently: 1 degree reduction per 1' of hose eliminated or if there are other variables? I will have to take another look at the plumbing to see if there are opportunities to eliminate any excess...

Can't say. My original post was from memory. I found my notes today, and my observations were as follows:

Before and after: 3 AC's online continously for 15 mins.
Before modification seawater temp 87.8 F inlet and 94.4 F outlet = + 6.6 degrees
After modification seawater temp 88.3 F inlet and 91.8 F outlet = + 3.5 degrees

In re-plumbing, I eliminated one elbow (at sea strainer) and added two for a net gain of one. The old hose had no interior growth. What I was initially focusing on was that hose getting in my way under the stbd engine. I recorded the stats, before and after, just in case I screwed up a good situation.

 

[oscarvan]

Me too. That's thick wall copper and bronze.

Ah.... painted white. Time for my annual eye exam.....