Spa blower overheating

I have a 220 volt 1-1/2 horsepower spa blower. It runs about 5 minutes then shuts off, I think due to overheating. It was very old, 15+ years old. And has never worked in the 10 years I have lived here. Took it apart to check the brushes (which were fine), but since the motor looked really rusted I figured it was bad.

I just purchased a new blower, and it also runs 5 minutes and shuts off. Darn it....

It is located 24 feet from the in-ground 8-foot round spa, but with no hartford loop. Total depth of spa about 3 feet or so, spa bubble air holes about 2 feet or so deep (around the seating area).

The wiring is 220 volt. Two 110 volt hot legs that come from an Intermatics timer box, and a ground. One leg runs straight through to the blower, the second leg runs to a on-off light switch to turn blower on-off.

Any ideas on this? I can't figure anything out.

New information:

I lifted the spa blower off the air pipe, and set it over to the side. I turned it on and ran it for 50 minutes free flowing sitting to the side with no backpressure on it. I also noticed that it ran very quiet. When it was on the air pipe it would be loud and scretching for 5 minutes then shut off.

So now I think I have ruled out the blower itself (it is new), and the electrical/wiring (works fine if I pull the blower from the air pipe). So now it looks like the stain on the motor is due to backpressure in the air line.

The spa has 25 holes around it on the seat. I drained the spa down to the level of the holes, then got in there and cleaned the holes out with a small screwdriver and a shop vac before installing the new blower. When the blower is running for the 5 minutes before it shuts off, air is blowing out of all the holes fairly agressively. Lots of air, lots of bubbles, and very large and violent bubbles.

I'm wondering if maybe I either need to install a hartford loop, or maybe even that the 1-1/2 horsepower blower is oversized for this installation. Maybe it is to powerful for this installation. I saw on another site someone recommended to someone else with a similar problem to install a T connector right below the blower with a valve and exhaust some of the air into the equipment area. So that the motor would get some free flowing fresh air to cool the motor.

I've moved the thread where others can see it, and several folks here may be able to help you. However, I will offer a couple of comments.

1. Most of us here who've worked in service over the years have learned the hard way to NEVER assume that "it" (whatever "it" is) works probably, just because it's new.

2. Motors usually trip because of excess current OR excess heat. In practice, these two usually are related. BUT, it will help folks help you to know whether the motor is tripping internally, or whether the external breaker is tripping.

3. Also, ratings matter. If you would look on the motor label, you should be find some like FLA or FLRA or RA (full load amps or full load running amps or running amps). Finding that value would be relevant.

4. If you can get your hands on a clamp-on ammeter, and can place it over one of the 220V wires during motor start-up, you'll be able to see exactly what amps your motor pulls, both during startup and during operation.

5. If you can also check the VOLTS, during startup, that can help identify current supply problems, like undersized wiring to the motor.

6. Finally, contrary to what most people think, centrifugal pumps overload during minimum flow restriction, not during maximum restriction. In your case, if there's not enough resistance to airflow, it could overload both your old and your new pump. In that case, simply installing a valve in between the pump and the spa, and throttling the valve till the amps (on the ammeter mentioned above) are in range, could fix your problem.

Good luck!

Ben

The blower is an Air Supply Silencer blower, 1.5 HP, 240 volts, 4 amps. It has an Amatek / Lamb motor in it (which pretty much all in-ground spa blowers have the Amatek/Lamb motor, the different manufacturers just wrap different pastic housings around it and stick different nameplates on it). The motor is what is tripping, not the breaker. The wires are #8 copper wire, on a 30 amp dedicated breaker, so that should be fine.

I think I fixed it. The blower originally sat directly on top of the check valve. What I did was add a PVC connector and short piece of PVC pipe (a couple inches). Then drilled a hole (about 3/8 inch) in the newly added short air pipe between the check valve and blower. I just ran the blower for about 40 minutes, and it ran fine. The hole in the pipe exhausts air into the equipment area. This then seems to have reduced the backpressure on the blower, and also allows the blower to move enough cool air over the motor to keep it cool and not overheat and cut off.

I also think I like it better now. Before the bubbles where very large and aggressive in the spa, almost uncomfortable. Now with relief hole that vents off some of the air, the bubbles are smaller and less aggressive. Maybe the blower was oversized to begin with, maybe a 1.5 HP blower is overkill for this installation, maybe a 1 HP would have worked better.

It's not clear to me how what you did fixed it, but spas and blowers are pretty much on the fringe of my experience, and I've learned that it's usually not a good idea to argue with success!

Glad you got your problem resolved.