I am looking for some advice on whether or not my furnace is short cylcing - or if there are other suggestions?
Immediately below is the set up and some context. The house, is 3500 sq feet excluding the basement (1500 sq feet), located in Canada's capital - with weather extremes of -35C to +35C. Currently -20C.
- A Goodman GMVC951155DX furnace (2007)
- Honeywell Vision Pro IAQ (2011)
- White Rodgers Humidifier (2006)
- Bryant ERV (2012)
- I recently had the ERV installed, along with a cold air return to the basement (there wasn't one before) and the installation of a furnace direct air intake pipe from outside (previously it was drawing air from the basement - which i suspect, now, may have been drawing/removing all the cold air that fell to the basement).
The new cold air return is 90% blocked given that the return is close to the furnace, and was drawing too much air - but it is still enough air even though I have partially blocked the return). If I unblock the new cold air return (completely) so that it sucks up the cold basement air, the furnace comes on and off 6 times in 20 minutes.
Prior to the new basement return, the house only circulated air from the first (main) and second floors. I realize there may be some insulation challenges in the basement, however the basement was much warmer before the changes.
The added difficulty, even with the current circutances (new cold air return largely blocked) is that the furnace is coming on for short periods. The temperature on the VisionPro thermostat aligns with what is called for, but the furnace only comes on for approx 5 minutes, and does not seem to be sufficient to warm up the house (it feels cold). As for gaps in between calls for heat, there are long gaps at high temperatures, but small amounts of time at low termperatures).
If I keep the house at a high temperature (I tried this, say 23C), the temperature in the house is maintained. However, if I keep the temperature at say 21C (70F), then the house gets cold despite the frequent calls for heat. I would have thought that if the the basement cold-air return was drawing more air than before, that the furnace would have come on more - and the house would have been warmer, not colder.
The technicians, as I understand, did not make any changes to the thermostat setup etc or change any settings on the HVAC, except to install the ERV controller next to the thermostat. Currently, the ERV is off in the above scenario.
What could be causing the furnace to short-cycle (on for short periods)?