Pneumatic Air Switch Controls


Modern Electronic Controls.

By James Arjuna

Dated March 4, 2002

A modern electronic control system has several safety features that make them much safer for modern spas and modern pumps.

To recognize the difference, a pneumatic controller has air buttons that depress quite a bit in order to actuate an air switch on the other end of a small tubing. They normally have a dial thermostat that is very sensitive to a slight change; a small turn will increase or decrease the temperature 3 or 4 degrees.


1/ The standard mechanical / pneumatic control boxes in common use are not electrically strong enough to run modern pumps over 2 HP 240 Volts or 1 HP 120 Volts. The standard control box is listed at 1.5 HP 240 V or 1 HP 120 V because of the air switch limitations of 2 HP 240 V maximum on the pump. In order to make them work on a 5 HP, 16.4 AMP pump, you would have to modify the box by adding a step-up higher amp relay and void the UL, or ETL label. Most building inspectors would not allow that.

2/ The standard mechanical boxes are not capable of having a blower and second pump clean-out. So, if you leave the blower off for months at a time (as in Colorado, Vermont, and Canada and other cold areas, for instance), the bacteria will build up, unless the owners run the second pump and blower to clean them out. (Electronic controls run these once or twice a day for 20 seconds to one minute, to insure sanitary water in the plumbing and air system). I suppose you could always just leave the blower off the spa and not have that to enjoy. The blower doesn’t work very efficiently on a full foam spa anyway.

3/ In a freezing cold climate, with the mechanical equipment we have now, it will stop running all together and freeze if the heater high limit trips. The mechanical controls will shut off the whole spa if there is a heater malfunction. (The solution is to have two high limits, one for the heater and one for the pump. But that doesn't exist on the mechanical controls we have now.)

4/ The mechanical controls being sold today have no automatic high (or low) speed jet pump shut off after 20 to 30 minutes. The high speed pump will keep running until the heater high limit trips off the spa. Electronic controls all have this shut off after 20 to 30 minutes. That means that the water in the spa with mechanical controls can reach 121 degrees, which is the heater high limit temperature, before the control box is shut off by the heater high limit. The liability on this could be horrendous for a spa builder. At 121 degrees human skin can become scalded, and older folks will pass out from the heat before they can get out. This is not good. I think that this is the number one reason for not using them unless you put a high limit, as in our digital electronic controls. On the Balboa, last time I checked, the limit is 112 degrees on the pump. It will shut off the pump at 112. On the Gecko it shuts off at 2 degrees above the set point on most. However, with the 20 minute shut down that is only available on the electronic systems (or Len Gordon hybrids), the spa will never reach that temp. There is a double safety system built in to the Gecko and Balboa.

5/ If the spa is shut down, as with an electric power failure or GFCI tripping, the spa with a mechanical timer on it, as in the mechanical/pneumatic packs, will come back on at the same temperature setting. This is because the thermostat is mechanical. But the filter times will be starting later by the length of time the power was off. On many of the electronic controls there is a reset temp of 95 to 100 degrees and 2 to 3 hours twice a day.

6/ Mechanical controls are simpler to fix for a qualified service tech with commonly available parts. Sometimes you can substitute parts with what you have in stock. Like using a double pole air switch to replace a single pole. (Just use one side). This is a big plus for the mechanical vs electronic.

7/ The latest version of most electronics is much more reliable than the mechanical controls, in my experience. It took quite a few years for the spa industry to get here.

8/ With air buttons you can put them under the spa cover or on the wall of the spa with no problems. With electronic topsides the moisture will eventually cause the overlay to become discolored or even fall off and have to be replaced. It simply is like a bumper sticker. You peel off the back and expose the glue and press it in place.

9/ The cost for repairs on a mechanical control are mostly in labor to diagnose and repair the problem. The parts are a lot less expensive for the repair, but in my experience the repairs happen more often, compared to the good electronics from Gecko and Balboa.

10/ Digital controls are much easier to set the temperature and control it accurately. With a mechanical control it is hard to get it set, but once it is set we recommend leaving it alone until seasonal temperature changes. Some run 103 in winter and 100 in summer. A slight turn on the thermostat will change up to 4 degrees at a time. The best way to set the mechanical thermostat is to adjust it to the highest setting and watch the spa. When it reaches the temperature you like, turn it down until is just goes off, then just nudge it up a tiny bit, until the heater light comes on. Or turn the heater down and when the water reaches the temperature you want , turn it up until it barely clicks on the heater. It will be within one degree of what you want. You do not want to keep turning the thermostat over and over, up and down; that will ruin them. With digital you can change the temperature as frequently as you want.

11/ The cost to repair a digital controlled spa can be more if the service guy has to use new boards. We use rebuilt or take the customer's board in to be rebuilt. The diagnostics is really fast on a circuit board. Once you find the problem is the board, (It doesn't matter what the problem is), you change it. There are only two service technicians I have heard of who will repair circuit boards in the field. The parts are cheap enough, but the labor needs to be somewhat skilled to diagnose the problem, then remove the defective part and replace it with a solder gun. It takes a test bench in the service van to do that.

12 The digital controls have "self-diagnostic codes". This allows us to tell what is wrong quickly. By taking into account what the diagnostic code says and what the spa is doing, we can determine what parts to send along with the service person.

13/ Digital controls are more expensive to install in a spa, but have a lot of plusses for the owners of the spa. Mechanical controls cost a lot less and are often found on "bargain" spas.

Right now the concensus is in strong favor of the electronics for ease of operation, self-diagnostics, SAFETY reasons, and the electrical current limitations of the air switches.

I would like to see a hybrid system with:

I prefer to have a digital temperature control for easier temperature setting. If a mechanical / pneumatic control had all this it would improve function and safety.

Some more detailed information

Since about 1995 the motor companies have been making stronger and stronger HP (horsepower) motors in theses smaller frames for spa. Many years ago, before there were spas, a 5 HP motor was huge in physical size, and much too large to fit under a spa skirt.

When portable spas first hit the market, they mostly used swimming pool pumps that had either 1 to 1.5 HP and they pretty much had one pump. Those pumps ran much cooler for two reasons:

1/ They used a "service factor" of 1.4 or more on the motor. That means the pump’s motors were oversized for the load, and this helped them to run much cooler. I still see old 1986 vintage Sundance spas with the Starite pumps with service factors in a closed cabinet in front of the spas. While the pump was on high speed, you could place your hand on the motor and not get burned. Not any more. Even so there have been cases of Sundance spas going into a continuous high speed operation because of a control failure and causing super hot water in the spa. I am not picking on Sundance, because Sundance was the best spa made in 1986, in my opinion. This is just for a point of discussion.

2/ They were only 1 to 1.5 HP. Today you can’t find many spas with that weak of a pump, except for the old fashioned Hot Spring spas. At 1.5 HP they don’t move much more than 90 GPM tops. Today’s pumps are moving over 200 GPM in some spas.

If you take a modern high efficiency motor and put it on a mechanical control system that does not have a 20 minute shut off, the spa can keep on running until the high limit in the heater cuts off the whole spa. The water is very unsafe at 121 degrees and people have been known to jump in without testing the temperature. That could kill an elderly person or anybody with heart or blood pressure problems.

The problem is that these controls are still being used on spas and they are being used with modern high energy efficiency motors, which were not in existence when the first mechanical / pneumatic / air switch controls received their UL or ETL approval.

I think the whole thing needs to be reevaluated by UL and ETL, because even a 1.5 to 2 HP modern pump runs a lot hotter than the old pumps back then. That makes the old mechanical / pneumatic control unsafe to use with the newer motors and especially in a thermal pane spa of any type. If the equipment were outside the skirt that might be OK, but why?

The modern electronic controls have redundant safety features that make them 500 times safer. I still think there are more things that can be done to make spas a lot safer. It is like building a spa to save that one child who has no clue what a hot tub is. When the last child is harmed forever, I’ll be very happy.

Here are some of the safety things we are developing:

Suction cover shut off. If the suction cover is removed the spa pump attached to that suction fitting is inoperable. The only way to run that pump is to replace the suction fitting. If the suction fitting is gone the spa won’t work. This is a lot better than the "vacuum operated" safety suction shut down system. With a vacuum switch, by the time the switch is activated by a vacuum change the little girl’s hair is already in the fitting and that may be too late. When the hair is on it’s way down the drain hole, it doesn’t create enough vacuum change to kill the pump until the largest part of the hair hits the opening and creates the vacuum change to actuate the switch.

High limit sensors on the individual spa pumps that shut off each pump from running if the water in the spa reaches 112 degrees. At 112 the user can get out of the tub without being burned or without passing out. Even someone with a slight heart condition can sense the water is too hot and exit the spa, before it renders them helpless. This is in addition to the automatic 20 minute shut off that we have now and the 2 degrees over the temp shut down on the Gecko controls. This would be another level of redundancy on this very real problem. This problem is not addressed at all in the standard UL / ETL controls with mechanical /air switches. That is why I deem those controls to be unsafe.

I had a lady call me about 7 years ago who had jumped into a spa that was hot enough to cause second degree burns on her legs. She told me that she always just opened the cover and got in for many years out of habit. The spa had never failed her before it burned her.

She wanted me to testify against the spa company in court, but I didn’t want to. The spa company has since gone out of business. I told her to never, ever go into a spa unless you check the temperature at least with your finger and that she should have a thermometer to check before she goes in again. That advice was too late, because she said that she was "never" going to get into a spa ever again. That is a tragedy, because she loved the tub before it burned her.

It is a lot different when you have an actual person on the phone compared to some statistic or a newspaper article. It "hits home" real hard and you never forget that conversation and the suffering she went through. I was burned, by gasoline, when I was in my early 20’s. I still have the scars, 34 years later. Burns are some of the most painful types of injuries there are. By the time I reached the hospital, I was screaming in agony.

Don’t buy a spa with a modern pump and a mechanical/pneumatic control system. If you have one of these spas, you may want to change the controller to a modern electronic system.

I have seen spas that were outside in Colorado in which the owners never ran the blower for months at a time. The blower on those old spas just blew in freezing cold air, so they were never turned on until Spring. I turned one on one time and this black, disgusting slime rose out the air holes. It looked like black mucus. If you buy a mechanical / pneumatic control without the 30 second or so daily clean-out on the blower, you will have to remember to turn it on once a day, or at least three times a week, to clean out the bacteria from the air chamber. Some sales pitches today use that as a reason to not have a blower. I really like a good warm air injection system, like we have in the Haven Spas and Emerald Spas. If you have an electronic control, that is not a problem or even something to think about, because it is automatic.

I have seen some spa companies who operate a cheaper spa business. In order to keep the prices down, they use a mechanical / pneumatic controller. The problem is they are often voiding the UL or ETL sticker by placing it in a spa that is not designed for that type of controller. Often you will see 3 HP or more pumps on those 2 HP air switches. This is just asking for trouble. The switches are arcing much more and the switch contacts are burning out quickly. The motors are starved for proper starting voltage and that ruins the motors as well. If you are considering a spa with a pneumatic control with air buttons, make sure, at least the pump motors are not stronger than the switch rating. Never use a 2 HP pump on a box rated for 1.5 HP 240 volts or even a 1.5 HP 120 Volt pump on the same switches that are rated for 1 HP with 120 Volts. When you have a 240V pump, the amp draw is less because the power come from both Amps and Volts combined.

Copyright 2002, Havenmade Inc. You may download this for personal reference as a consumer. No use is permitted by any commercial company or individual. You may not resell this information or publish it in any format without the written permission of the author and Havenmade Inc.