Cooling system performance

I set out for our vet's office this morning. The temperature was 24 degrees. I have a scan gauge with coolant temperature selected. The engine temperature rose as I drove the 10 miles to our vet's office. There are two traffic lights, two roundabouts and a stop sign near my home and then a county road with a 55 mph speed limit for the last 8 miles of the trip.

As the coolant temperature rose above 105 degrees the heater blower switched on to 1 bar on the display. I always feel a stream of cold air momentarily on my feet when the blower turns on. Temperature gradually increased and blower speed increased to an indicated 5 bars. The temperature at that point was 180 degrees. The last 5 miles of the trip the temperature never exceeded 180 degrees. The heat extracted from the engine by the heater core while warming a cold cabin with 5 bars of indicator blower speed prevented the coolant temperature from going above 180 degrees.

At the vet's office I sat there waiting for a prescription for our dog to be filled. The ICE cycled on at 115 degrees and off at 130 degrees while I was waiting and the heater blower eventually dropped back to 3 bars as the cabin warmed to the target of 72 degrees.

On the return trip with the cabin warm, the temperature gauge increased from about 130 degrees to 195 degrees about halfway home.

I have noticed in winter city driving that when the ICE is above 130 degrees, the ICE switches off at traffic lights and during deceleration and engine temperature never reaches 195 degrees. It takes some getting used to.

Just wanted to point out that there is not much wasted heat with this vehicle.

 

I only mentioned this because as with our first home with a heat pump, it took some getting used to. You don't stand over the warm air register with a heat pump because the discharge air is only in the 75-90 degree range as opposed to the 130 degree range with a gas furnace. The heat pump must run longer cycles to maintain the temperature which actually makes it a more even heat than with a gas furnace with shorter heating cycles.

The same is true of the PriusV. In winter city driving, the discharge air is cooler because the ICE keeps shutting off at traffic lights and on deceleration. The coolant temperature remains well below the 195 degree thermostat limit. It takes longer for the cabin to heat up. It's the price you pay for a fuel efficient vehicle. On the freeway where the ICE stays on, it heats up like any other vehicle.

 

I agree.
I have a digital thermometer that I use to periodically check my heat pump performance and record the readings. This morning it was 11 degrees in Columbus. Our setpoint is 68 degrees and today my heat pump return air was 66 degrees and the supply air was 77 degrees. (11 deg delta) This is a 16 SEER, 2 speed heat pump with 2 stages of electric strip heaters in the air handler. That provides us with 3 heating levels. (Low compressor/high compressor/high compressor plus strip heaters) It locks out the compressor below 5 degrees and then just uses both stages of strip heaters. Today I suspect, it will cycle between high compressor and high compressor plus strip heaters. Lots going on in a Honeywell thermostat that manages all of that.

Our home is all electric and with our low electric rates, our budget is $117/month. One more reason for our next vehicle to be electric.