Why not a dehumidifier?

[flapjake314]

So when the outside air temp is very cold I try to keep the car circulating inside air. However per other threads, Ford programmed the HVAC to turn this off after a few minutes to prevent fogging of the windows. However it never turns it back on either...

Most experts agree the energy savings of a heat pump is minimal particularly in extreme cold, but why not just a dehumidifier so you can keep recirculating cabin air? Trying to heat -20F air to be 70F is not a great idea...

FMC you can DM me for my address to mail me a "good idea" check haha jk, but am I missing something, would that solve a lot of issues?

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[RickMachE]

Dehumidifiers generate a lot of warm air, and copious amounts of water. Water draining out would freeze, and the tube would clog.

 

[flapjake314]

Dehumidifiers generate a lot of warm air, and copious amounts of water. Water draining out would freeze, and the tube would clog.

MY2024 mach-e now with in-cabin water dispenser

 

[Mach-Lee]

Dehumidifiers don't work below freezing because the moisture would freeze on the evaporator. The Mach-E A/C compressor will not run when it's colder than 32ºF outside, so no dehumidification is possible below that temp.

Below 32ºF you dehumidify the cabin by taking in (dry) outside air.

When it's -20ºF heating outside air is the only option, recirc will fog the windows up almost instantly due to the cold glass surfaces requiring a very low interior dewpoint. The heater is not powerful enough to heat the air from -20ºF to 70ºF. This is why the Mach-E shouldn't be used when it's that cold.

 

[KadeBR]

Few found out the recirc will stay on if it only blows out main vents don't use defrost of feet. Then just hit max defrost as needed and hit it again to revert to previous settings if you use remote start last settings it will have the cabin comfortable in 5 min.

 

[flapjake314]

The Mach-E A/C compressor will not run when it's colder than 32ºF outside, so no dehumidification is possible below that temp.

i understand the existing one doesn't work this way, but why can't it run a dehumidifier inside the cabin like i have in my basement?

yes it'll create a bucket of water but you can imagine it getting pumped out once every [30] minutes so it doesn't easily freeze etc

 

[A-A-Ron]

but why can't it run a dehumidifier inside the cabin like i have in my basement?

yes it'll create a bucket of water

I love when you answer your own question. Honestly, it’s a smaller engineering project for Ford to add a larger heater than to deal with buckets of water inside your cabin.

 

[Phrozen]

When it's -20ºF heating outside air is the only option, recirc will fog the windows up almost instantly due to the cold glass surfaces requiring a very low interior dewpoint. The heater is not powerful enough to heat the air from -20ºF to 70ºF. This is why the Mach-E shouldn't be used when it's that cold.

Yeah, I've gotta disagree here on the "shouldn't be used" part. I drove my Mach-E in the -40s the week before Christmas, and between the various heaters (seats and wheel and defrost) and dressing appropriately, it worked just fine. In fact I at one point stopped to help out a stuck car, and my wife had to turn the heat down after 10 minutes or so.

 

[Ron Bonifas]

I love when you answer your own question. Honestly, it’s a smaller engineering project for Ford to add a larger heater than to deal with buckets of water inside your cabin.

I don't believe a household sized dehumidifier (which way about 50lbs.) would pull moisture out of the cabin quickly enough to keep windows from fogging. I don't want the wife asking why we're driving around with an inverter and a running dehumidifier in the back seat so I'll leave that experiment up to a more optimistic individual.

 

[flapjake314]

I don't believe a household sized dehumidifier (which way about 50lbs.) would pull moisture out of the cabin quickly enough to keep windows from fogging. I don't want the wife asking why we're driving around with an inverter and a running dehumidifier in the back seat so I'll leave that experiment up to a more optimistic individual.

but you're saying if i wear one of those fighter jet masks it'd work?

 

[Ron Bonifas]

but you're saying if i wear one of those fighter jet masks it'd work?

Maybe! I'm curious now how fighter jets etc. have dealt with extreme cold at high altitudes.

 

[AZBill]

Maybe! I'm curious now how fighter jets etc. have dealt with extreme cold at high altitudes.

Bleed air from the jet engine, very hot. That is how they keep you warm at 35000 feet.

 

[Mach-Lee]

i understand the existing one doesn't work this way, but why can't it run a dehumidifier inside the cabin like i have in my basement?

yes it'll create a bucket of water but you can imagine it getting pumped out once every [30] minutes so it doesn't easily freeze etc

A few things wrong with that:

1. Refrigerant dehumidifiers are only effective down to 30% RH. Below that they are extremely inefficient to run and struggle to remove any more humidity. In the winter single digit humidity levels are required in the cabin to prevent window fogging, far below what refrigerant units are capable of.
2. Packaging. Where are they going to put this extra dehumidifier?
3. Liquid water in freezing environment. This would require a heated drain pain and drain wasting more energy.

In winter temps the only practical way to dehumidify the cabin is to bring in fresh air. You can’t dehumidify it with a refrigerant system because the dew points are too low.

Yeah, I've gotta disagree here on the "shouldn't be used" part. I drove my Mach-E in the -40s the week before Christmas, and between the various heaters (seats and wheel and defrost) and dressing appropriately, it worked just fine. In fact I at one point stopped to help out a stuck car, and my wife had to turn the heat down after 10 minutes or so.

You must not have been moving very fast, there’s no way it will keep up on the highway at -40° for long. The convective loss from the wind is a huge thermal load. I ran out of heat on the interstate when it was only -10°F. If you heat up the car before leaving and only drive slow around town you might make it for a few minutes at -40° but if you get on the highway you’ll freeze after 30+ minutes.

Maybe! I'm curious now how fighter jets etc. have dealt with extreme cold at high altitudes.

Bleed air from a jet engine is very warm, hundreds of degrees. There’s more that enough heat being generated by a jet engine to heat anything you want. You could heat a jet cabin to 100°F if you wanted to.

 

[Ron Bonifas]

A few things wrong with that:

1. Refrigerant dehumidifiers are only effective down to 30% RH. Below that they are extremely inefficient to run and struggle to remove any more humidity. In the winter single digit humidity levels are required in the cabin to prevent window fogging, far below what refrigerant units are capable of.
2. Packaging. Where are they going to put this extra dehumidifier?
3. Liquid water in freezing environment. This would require a heated drain pain and drain wasting more energy.

In winter temps the only practical way to dehumidify the cabin is to bring in fresh air. You can’t dehumidify it with a refrigerant system because the dew points are too low.





You must not have been moving very fast, there’s no way it will keep up on the highway at -40° for long. The convective loss from the wind is a huge thermal load. I ran out of heat on the interstate when it was only -10°F. If you heat up the car before leaving and only drive slow around town you might make it for a few minutes at -40° but if you get on the highway you’ll freeze after 30+ minutes.



Bleed air from a jet engine is very warm, hundreds of degrees. There’s more that enough heat being generated by a jet engine to heat anything you want. You could heat a jet cabin to 100°F if you wanted to.

I'm sure there is plenty of waste heat and fuel efficiency is not a top priority in a jet fighter!

A few things wrong with that:

1. Refrigerant dehumidifiers are only effective down to 30% RH. Below that they are extremely inefficient to run and struggle to remove any more humidity. In the winter single digit humidity levels are required in the cabin to prevent window fogging, far below what refrigerant units are capable of.
2. Packaging. Where are they going to put this extra dehumidifier?
3. Liquid water in freezing environment. This would require a heated drain pain and drain wasting more energy.

In winter temps the only practical way to dehumidify the cabin is to bring in fresh air. You can’t dehumidify it with a refrigerant system because the dew points are too low.





You must not have been moving very fast, there’s no way it will keep up on the highway at -40° for long. The convective loss from the wind is a huge thermal load. I ran out of heat on the interstate when it was only -10°F. If you heat up the car before leaving and only drive slow around town you might make it for a few minutes at -40° but if you get on the highway you’ll freeze after 30+ minutes.



Bleed air from a jet engine is very warm, hundreds of degrees. There’s more that enough heat being generated by a jet engine to heat anything you want. You could heat a jet cabin to 100°F if you wanted to.

A few things wrong with that:

1. Refrigerant dehumidifiers are only effective down to 30% RH. Below that they are extremely inefficient to run and struggle to remove any more humidity. In the winter single digit humidity levels are required in the cabin to prevent window fogging, far below what refrigerant units are capable of.
2. Packaging. Where are they going to put this extra dehumidifier?
3. Liquid water in freezing environment. This would require a heated drain pain and drain wasting more energy.

In winter temps the only practical way to dehumidify the cabin is to bring in fresh air. You can’t dehumidify it with a refrigerant system because the dew points are too low.





You must not have been moving very fast, there’s no way it will keep up on the highway at -40° for long. The convective loss from the wind is a huge thermal load. I ran out of heat on the interstate when it was only -10°F. If you heat up the car before leaving and only drive slow around town you might make it for a few minutes at -40° but if you get on the highway you’ll freeze after 30+ minutes.



Bleed air from a jet engine is very warm, hundreds of degrees. There’s more that enough heat being generated by a jet engine to heat anything you want. You could heat a jet cabin to 100°F if you wanted to.

I'm sure there's plenty of waste heat from a fighter jet engine and fuel efficiency isn't a top priority. Not to relevant to passenger vehicle. Sorry...thanks for answer thou

 

[Phrozen]

You must not have been moving very fast, there’s no way it will keep up on the highway at -40° for long. The convective loss from the wind is a huge thermal load. I ran out of heat on the interstate when it was only -10°F. If you heat up the car before leaving and only drive slow around town you might make it for a few minutes at -40° but if you get on the highway you’ll freeze after 30+ minutes.

The one day I remember exactly where I was driving, the route was ~12 miles, 20 minutes, from the airport (where the car had been sitting plugged in but cold-soaked for almost a week) home, on roads with speed limits of 45, 40, 55, 45, 30, 20 in that order. There aren't a lot of wide open interstate highways in Fairbanks, Alaska, but we do indeed get plenty of cold weather. And I can confirm that the Mach E will indeed handle real winter temperatures.

But like I said, this is coming from someone with a lifetime of winter driving experience, so maybe "dressing appropriately" means something different to me than it does you.

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