Burned out air conditioner circulation pump

[ttex]

I installed this air conditioner and everything myself about 2 years ago and it's more or less been running great until last night. I woke up with the air conditioner off and found that it had shut itself down because the circulation pump was not running.

I smacked it a couple of times with a wrench and it started moving around but it wouldn't pump. I did get a quick wiff of burning plastic smell. Not strong and didn't last very long.

I disassembled the pump and checked the diaphragm and everything and it all looked good so I reassembled it and reinstalled it and it started working just fine.

After running for about 20 minutes the breaker for my air conditioner circuit tripped at the panel and when I went to look at the air conditioner area I could smell a strong burning plastic smell.

With that all out of the way I'm pretty sure I know what's going on I just want to run it by y'all and see if there's something I'm missing. When I first installed the circulation pump I was supposed to put a 1.5 amp fuse for the pump but I completely forgot. At this point what I think happened is that as the strainer would clog the amps would rise and as it wasn't being protected this continued for a while every time the strainer would clog and eventually it burned out the wiring inside the pump or the windings themselves.

The motor is surely toast.

Basically my theory is that this happened because I forgot to install the 1.5 amp fuse. Does anyone disagree?

[Rohan]

What type of A/C was it? What brand?

[ttex]

Webasto Platinum 12k btu

Circulation pump is a Shurflo AC circ pump 4.5 gpm

Circulation pump runs off of a relay that is activated by the Webasto system.

[ttex]

Wiring is 10 gauge. The circuit breaker for the air conditioner is 20 amp

[ttex]

I disconnected the circulation pump and the air conditioner will start up and run. I turned it off before it errors out because the circulation pump is not on. As soon as I reattach the circulation pump and turn it on it trips the breaker

[JoeRobertJr]

Originally Posted by ttex

...The motor is surely toast.

Basically my theory is that this happened because I forgot to install the 1.5 amp fuse. Does anyone disagree?

Hi, ttex,
Your theory sounds completely reasonable to me - that a fuse might have prevented the windings from overheating when the pump became heavily loaded. Lousy situation, but experience makes us wiser. I am installing a pump myself and making sure I include the 3-5A fuse spec'd by the manufacturer. I'll start with a 3A and see what happens. I'll also put a label on the fuse holder as a reminder to my future self.

[Madehn]

No this does not sound right. Your pump would not be protected by a 1.5 amp fuse. They draw more power than that on a normal basis. The contro circuitry in your AC box may have needed that fuse. If something fried it is more likely that it is in your ac box than in the pump itself. The pump might draw more amps as flow became restricted but more likely your control circuit was called upon more often as flow became restricted then went into staying on continuously as the AC unit was continuously asked for cooling Normally the AC unit would then shut down if that cooling did not happen and show a high pressure fault code. Guessing that something in your ac control box fried. Just my best guess. Good luck with it. You can swap out pumps on a temporary basis and see if pump is the issue but my guess is that your fault will be in the control board for the AC unit.

[ttex]

Originally Posted by Madehn

No this does not sound right. Your pump would not be protected by a 1.5 amp fuse. They draw more power than that on a normal basis. The contro circuitry in your AC box may have needed that fuse. If something fried it is more likely that it is in your ac box than in the pump itself. The pump might draw more amps as flow became restricted but more likely your control circuit was called upon more often as flow became restricted then went into staying on continuously as the AC unit was continuously asked for cooling Normally the AC unit would then shut down if that cooling did not happen and show a high pressure fault code. Guessing that something in your ac control box fried. Just my best guess. Good luck with it. You can swap out pumps on a temporary basis and see if pump is the issue but my guess is that your fault will be in the control board for the AC unit.

The pump is definitely the issue. That is not in doubt. I just now replaced the pump and everything's working fine. The pump does call for a 1.5 amp fuse for protection and these fuses do protect the pumps. This is 120 volt so that may be why you're confused with the 1.5 amp.

Also, this 120 volt circuit does not touch the boards and sensitive stuff in the air conditioner. Those are powered off of a transformer that goes down to 24 volts. Which is of course protected by their fuses inside the unit itself.

[HopCar]

I curious about the pump. I don’t think ShurFlo makes a suitable pump for AC use. The one you are using is way too small for a 12K BTU AC. Webasto recommends a 1000 gallon per hour pump for that AC. Take a look at the March AC-5C-MD. It’s not self priming so it would need to be mounted below the waterline.

[thinwater]

I kinna doubt the fuse would have made a difference. Centrifugal pump amps typically do not go up that much with restriction. In fact, often they go down (higher head, but less flow). Haven't you heard a vacuum cleaner or fan speed up when the suction is blocked? It's not like a gear or diaphragm pump. The fuse only helps if there is a locked rotor (something jamming the impeller). More likely just poor quality on that unit. Maybe a seal failure.

[Capt Clark]

Originally Posted by HopCar

I curious about the pump. I don’t think ShurFlo makes a suitable pump for AC use. The one you are using is way too small for a 12K BTU AC. Webasto recommends a 1000 gallon per hour pump for that AC. Take a look at the March AC-5C-MD. It’s not self priming so it would need to be mounted below the waterline.

A real Hopkins Carter guy would recommend the better March pump…. the
LC-5C-MD. Especially if it’s installed in the engine room.

[HopCar]

Originally Posted by Capt Clark

A real Hopkins Carter guy would recommend the better March pump…. the
LC-5C-MD. Especially if it’s installed in the engine room.

You’re right, just seemed the guy was working on a budget.

For those who are curious, the AC-5C-MD is an air cooled pump.
The LC-5C-Md is a liquid cooled pump. I believe it is also submersible.

[Scrimshaw4]

Just 5 weeks ago I had a "Nettle" aka Jelly Fish clog my AC's strainer. Not only did the March Pump burn up, it also took out the relay control board because a fuse was not installed between the two! Apparently when it was installed it was believed that the pump had it's own internal shutdown protection. Mine was the liquid cooled model and yes all their magetic drive centrifical pumps not self priming so they have to be installed below the waterline. There's a fuse there now!