McDonnell Miller pump control/LWCO

Jeffro3

Heya Folks;

I'm running two 13 section Burnham boilers and they both have McDonnell Miller 150shd pump control/lwco. These were installed in the last 4 years. They both run great except for the pump controls. I keep flooding the boilers because the switches go bad. I blow the system down every Monday, and I've changed the micro switches multiple times, but they wear out rather quickly with winter cycling.
The company changed to micro switches over the reliable mercury switch and sells only the new ones at a high price.
I'm wondering if anyone else has run into this, what they did, or if there's another manufacturer that makes a better unit.

tim smith

You are probably running too much amperage through

contacts, are you switching the motor through a contactor or direct for condensate? We have ran into this problem several times.

The Boiler Dr.

Poor quality M & M switches

I have had 5 failures out of 12 new control installs. I am not the only one either. Those new micro switches are JUNK!
If the switch can't take a 3.5 to 5 amp load when rated for twice that there is surely something wrong.

Jeffro3

interesting

Hmmmm,Interesting idea about the contactor. It would be a smaller draw to pull in a coil, tho the switch is rated for 15 amp. Tx, I'll probably put one in during the summer.

It's also nice to know someone else has seen this and I'm not nuts (at least about this ). Isn't interesting how they'll only sell you both switches on the mounting plate for 500.oo + ? I supose it's the liability thing so that you're not running the water too low. I get mine from MSC for 4.oo and just make sure it's adjusted for the proper level.

tx much for the response.

The Boiler Dr.

BTW

Which switch gave you trouble? 3-wire LWCO or 2-wire pump?

Jeffro3

which switch

The 2 wire pump control as it gets more cycles than the LWCO.