Hacking a condensing boiler blower

November 2015

I needed a blower for various projects, and had liberated on from our Worcester Bosch Greenstar condensing combi boiler before it went to the scrappers.

The blower is an EBM Papst RG130 model. The product data shows it will shift about 140 cubic meters per hour (about 85 CFM). This is a bit weak for many applications but I decided to go ahead anyway…

The plug has five connectors. Pulling the plastic cover revealed some helpful writing on the PCB (left to right):

  • 230V (two connectors – no indication of live/neutral)
  • GND – ground for PWM and HS
  • PWM – speed control, more on this below
  • HS – Hall Sensor, an output for RPM (2 pulses per rev)

I found out a good deal of info from this document: http://www.ebmpapst.com/media/content/info-center/downloads_10/catalogs/heizung/Condensing_boiler_technology.pdf

Sadly however, no information on the PWM speed control. The PCB includes some text “+14V” which suggests that this is the high value of PWM. Also the specs for model RG128 state max RPM is ~7,000, so if monitor the motor speed I should be able to work out when I am getting close to the PWM max.

Next steps:

  • mount the bugger and attach a 230V switch
  • start with 5V on the PWM line and work up from there
  • use an Arduino to measure RPM

More… later…