Bosch Thermotechnology US customer service: 1-866-642-3198. Hours: Monday-Friday, 8 AM - 8 PM Eastern. Typical hold time 10-15 minutes.
What to have ready
- Model number — from the data plate on the side of the unit
- Serial number — same plate
- Error code if displayed
- Install date if you have records
- Symptom summary — what happened, when, what changes
- For Greenstar combi: heating system description (radiators, baseboards, in-floor; primary/secondary?)
What Bosch support can do
- Walk you through error code diagnostics over the phone
- Confirm warranty coverage by serial number
- Dispatch parts to a Bosch-trained installer (not direct to homeowner)
- Locate the nearest Bosch-trained installer (and hydronic-specialist for Greenstar)
- Email the installation or owner manual
- Help with Home Comfort app pairing
- Escalate complex combi issues to field engineering (24-48 hour response)
What they won't do
- Ship parts directly to a homeowner
- Dispatch a technician — that's the installer's job
- Help with hydronic system design beyond what's in the Hydronic Piping Guide
Other contact points
- Sales / wholesale: regional Bosch sales rep through your installer
- Email: service@bosch-thermotechnology.us
- Hydronic engineering escalation: through the main line for combi-specific questions
Bottom line
Bosch phone support is technically competent on Greentherm tankless. For Greenstar combi questions specifically, the field engineering escalation can be slow (24-48 hours) but the answers are authoritative. For Tronic POU mini-tank issues, the phone support is straightforward — these are simple products.