Better pressure switch

[imagineer]

Can anyone suggest a better air compressor pressure switch that this?

MDR11 (USA) Air Compressor Switch

The MDR11 (USA) Water Pump Pressure Switch from Condor USA. 2-pole Single Phase (N.C.) Def. Purpose Switching Capacity: 26 FLA/156 LRA up to 240V Gen. Purpose Switching Capacity: 2 HP @120V 3 HP @240V NEMA A600 Pilot Duty Acc. to EN 60947 4.0 kW (AC3), Ue=240V (1~) Cut-out pressures up to 225...

condor-usa.com

I replaced the switch on my (5hp, 60gal Husky single stage) compressor 3 times in the last year and the one I installed on 6/6/26 failed yesterday.
I need a 135/100 psi switch.

 

[OccupantRJ]

Does the unit have a magnetic starter? If not, there's the problem. A 3 hp rated switch contact set won’t likely last long trying to run 5 hp directly through it.

 

[Hohn]

Does the unit have a magnetic starter? If not, there's the problem. A 3 hp rated switch contact set won’t likely last long trying to run 5 hp directly through it.

Exactly. You simply can't ask a set of pressure switch contacts to make/break way over its rating and last very long.

You want a mag starter to take the load off the switch to the switch just acts like a relay.

 

[OccupantRJ]

I have not used one myself but have read that some guys are using the Weg starter. The entire unit is cheaper than some of the replacement contacts in some of the older well known brands of starters I dealt with at work, and overload setting is adjustable.

WEG 5 HP 1 Phase Magnetic Starter NEMA 1 208-240V 22-32 Amps ESWS-25V24E-RM34

Shop the WEG ESWS-25V24E-RM34 5 HP single-phase magnetic starter with NEMA 1 enclosure. Reliable motor control for efficient and safe operation.

compressor-source.com

 

[imagineer]

No, the compressor doesn't have a magnetic starter, nor did it when I purchased it (used) about 20 years ago. The original pressure switch that failed about this time last year was nearly identical to the 2 that have been installed since.

 

[Hohn]

I have not used one myself but have read that some guys are using the Weg starter. The entire unit is cheaper than some of the replacement contacts in some of the older well known brands of starters I dealt with at work, and overload setting is adjustable.

WEG 5 HP 1 Phase Magnetic Starter NEMA 1 208-240V 22-32 Amps ESWS-25V24E-RM34

Shop the WEG ESWS-25V24E-RM34 5 HP single-phase magnetic starter with NEMA 1 enclosure. Reliable motor control for efficient and safe operation.

compressor-source.com

Given the very reasonable price, I'd buy that in a heartbeat if I were OP. It would solve the pressure switch issue forever.

 

[Hohn]

No, the compressor doesn't have a magnetic starter, nor did it when I purchased it (used) about 20 years ago. The original pressure switch that failed about this time last year was nearly identical to the 2 that have been installed since.

Right, so I think you're seeing evidence that yet another switch is the definition of insanity, as they say. You need a mag starter because your motor is probably a bit marginal for the compressor. Husky isn't exactly using top of the line hardware in the BOM and the fact that this compressor is rated only 100/135 is sort of a giveaway at how weak the motor is.

Add the fact that as a box store compressor without any unloaders, the marginal, low-cost motor is having to start against tank pressure and you get a high inrush that eats pressure switches.

Husky's engineering team almost certainly knew this would happen and they just shoulder shrugged and decided "meh, consumer usage, it's good enough."

Get the mag starter. It will solve the problem until the problem moves to be the motor instead of the pressure switch.

 

[OccupantRJ]

Right, so I think you're seeing evidence that yet another switch is the definition of insanity, as they say. You need a mag starter because your motor is probably a bit marginal for the compressor. Husky isn't exactly using top of the line hardware in the BOM and the fact that this compressor is rated only 100/135 is sort of a giveaway at how weak the motor is.

Add the fact that as a box store compressor without any unloaders, the marginal, low-cost motor is having to start against tank pressure and you get a high inrush that eats pressure switches.

Husky's engineering team almost certainly knew this would happen and they just shoulder shrugged and decided "meh, consumer usage, it's good enough."

Get the mag starter. It will solve the problem until the problem moves to be the motor instead of the pressure switch.

It looks like the switch he referenced has unloader function.

 

[txvwnut]

You need a pressure switch rated for a 5hp compressor. The one you listed is rated for a 3hp which is why it failed.

 

[Hohn]

It looks like the switch he referenced has unloader function.

I see that now. Still massively underrated for the task at hand, as you mentioned.

 

[mm08822]

Not the fault of the 3hp rated PS controlling a 5HP motor.

Buy a 5HP rated PS and then there is no need for a motor starter.

 

[BillK]

was nearly identical to the 2 that have been installed since.

Can you find one that is identical ?

 

[imagineer]

The original and all replacements were Condor brand and marked "MDR 11/11EA". The only difference was the red knob on the original was a bit different. Apparently that model # covers a variety of switches and some are not rated for 5hp.

 

[Hohn]

The original and all replacements were Condor brand and marked "MDR 11/11EA". The only difference was the red knob on the original was a bit different. Apparently that model # covers a variety of switches and some are not rated for 5hp.

Condor has some good pressure switches-- the unit on my little 120V compressor has had a hard life for 20 years and is still kicking.
But no switch can survive being massively under-specified. It's not on Condor, it's on Husky for cheaping out and cutting a corner.

 

[mm08822]

I read it as the OP didn't use a properly rated replacement part and continued to do so 2 more times. A similar part from the same product family doesn't mean it's sized properly.

 

[yatg]

If you want to retain that style of pressure switch, use it to drive a contactor that will handle the load.

feed > pressure switch > contactor coil a1,a2
and
feed > contactor t1,t2 ... contactor l1,l2 > motor
feed > contactor L1,L2 ... contactor T1,T2 > motor

The pressure switch only has the load of the contactor coil, which is miniscule compared to the load of the motor.

Contactor example, 60A, stated good for 10hp @ 240v, but find something with a known name

https://www.amazon.com/Shopcorp-Contactor-Pole-220V-240V/dp/B0FRT8D84K/?tag=atomicindus08-20

 

[manwithtools]

feed > contactor t1,t2 ... contactor l1,l2 > motor

I think you got that swapped around, should be:

Feed > contactor L1,L2 ... contactor T1,T2 > motor

 

[yatg]

I think you got that swapped around, should be:

Feed > contactor L1,L2 ... contactor T1,T2 > motor

you're right L# is line (not load), T# is terminal side. fixed above. thanks.

 

[imagineer]

FYI, I found and ordered a pressure switch that's OEM on Ingersoll Rand single stage compressors with 5hp motors.

 

[OccupantRJ]

It will be interesting to see what the IR switch is rated.