There's a safety recall on Venmar HRV's.
They can overheat and cause a fire.
Go to www.venmar.ca for model and serial numbers of faulty ones.
We had a house fire close by that was caused by one of these over-heating.
From what I understand, they are sending homeowners an add-on kit to detect
an overload, but this is second hand news. They're closed for Christmas,
but I'll call their 1-800 hot line for further info.
In the meantime, unplug it if you have one.