The 154 model I bought did not have sufficient space between the heat plate and the cap, which caused a lack of airflow which then caused it to over-heat just after a few minutes of operation. The old one it replaced had about a 3/4" stand-off that allowed ample flow. If yours is restricted too, you may need to add something behind the plate screws to increase the separation between the two plates. I did that and it now moves air similar to the old one. If it wasn't for that, this one works just like the old one, which lasted 24 years.