My Air Handler is Possessed!

[PWMDMD]

I have a 3.5-year-old Bosch IDS 2.0 heat pump that has been working perfectly until now. I noticed about a month ago that the AH came on with the system off. It was a short 2-minute run with the outside condenser not running. I thought maybe it would automatically run periodically when the system was off to just keep the ducts clear or whatever. Then over the course the last few weeks it's been happening more and more with longer run times. This AM it ran for 20 mins. The system is OFF, the fan is set to Automatic and NOT circulation, and the dehumidification setting is off. I reset the thermostat and turned the breaker off and on to reset the system and it didn't help. I have a call into the service company.

Both the heat pump and thermostat are fairly sophisticated - does it should like a computer or thermostat (Bosch BCC-100) problem?

 

[Inked]

I know we have some members in the business but if I had to guess I would say it’s a thermostat issue.

 

[97prizm]

Sounds like a thermostat that's bad or low batteries in the thermostat. I'd remove the batteries turn the thermostat off and wait 20 minutes. Put the new batteries back in and set to your desired settings. Second do you have 2 air filters in use ie a pre-filter and a second fine filter? If so I had an issue with my parents newer furnace that is a high efficiency furnace. Certain combinations of a dual filter cause a restriction and longer run times.

 

[CDX825]

Literally just installed a bosch air handler the other day.

My suggestion would be to try unhooking G from the thermostat and see if it quits. If it does its a thermostat issue. If it doesn't its the control board in the air handler.

 

[Chevyc10]

Control board fan relay sticking.

 

[PWMDMD]

So the thermostat has a c-wire, no batteries. I removed the thermostat while the system was off and it has turned on and off several times so I'm going to go with the control board. A "senior tech" is coming out next Monday to troubleshoot. I figured I'd just turn off the breaker but interestingly, the breaker labeled A/C does not feed the A/C. It also seems to be happening more frequently.

Thank you everyone for the responses!

 

[Fitter30]

Page 10
https://www.bosch-homecomfort.com/u...ls/bcc100_advanced_settings_guide_01.2022.pdf

 

[facility1]

possibly bad/dirty return sensor

 

[PWMDMD]

Page 10
https://www.bosch-homecomfort.com/u...ls/bcc100_advanced_settings_guide_01.2022.pdf

Still cycles on and off with the thermostat disconnected completely.

 

[Sequoiasoon]

Subscribing for updates.

have a Bosch IDS 2.0 system and very happy with it. Mine has a 10 year maybe 12 parts and labor warranty. I had it installed about 3.5 years ago. AC works great, heats work well to supplement HW baseboard (or replace for shoulder seasons). Electric usage is down as compared to old CAC and oil usage is also reduced.

PSEG was doing deal so it was also interest free payments. Better option for me than raiding other funds.

 

[Nukeman7]

So the thermostat has a c-wire, no batteries. I removed the thermostat while the system was off and it has turned on and off several times so I'm going to go with the control board. A "senior tech" is coming out next Monday to troubleshoot. I figured I'd just turn off the breaker but interestingly, the breaker labeled A/C does not feed the A/C. It also seems to be happening more frequently.

Thank you everyone for the responses!

Still cycles on and off with the thermostat disconnected completely.

This certainly pinpoints it to the HVAC master control board. In my experience, the newer HVAC units with inverter technology have control boards that are more sensitive to under/over voltage fluctuations. It may be good insurance to install an in-line surge protector if the repair technician determines the control board has failed.

 

[PWMDMD]

Well, he initially thought it was the control board but as soon as he replaced it, the fan turned on when it shouldn't have, and then he knew it was the blower itself. He replaced the blower and there are no issues anymore. We have a 10-year parts warranty but still pay labor and he completely deducted any labor time concerning the control board. I thought that was very fair.