View Full Version : dual zone heat?
The boss and I have different levels of comfort for temperature and the amount of air blowing on us. So, I am considering running two heating coils in series, one for each side of the cockpit, coolant leaving the engine running through the PS first then through the DS coil. I do not have a glove box, so think I have enough room physically to mount two units. But, I am now unsure of the coolant temperature leaving the first coil used to heat the air for the second coil. Air entering the first coil should be between 185-200 degrees, but I cannot find any data on what the outlet temperature may be, which would be the inlet temperature for the DS heating coil. Anyone have any guesstimates on the coolant temp leaving a heating coil? Or any other fundamental flaw I should consider?
Thanks in advance
JJ
PS. I also plan on heated seats, so this is in addition to...
Nigel Allen
02-25-2023, 12:15 AM
I was thinking about a similar idea and I reckon it would work well, just tricky finding the room for 2 heaters. I only installed one and it does a pretty good job. If I build another Roadster I would aim to do 2 like you have suggested.
1. Put 5/8" Y pieces in you supply and return lines.
2. Make the lines the same total length for each heater. to ensure even flow restriction / balance to each core.
I haven't yet fitted seat heaters, but likely will for this winter.
Cheers,
Nige
mladen
02-25-2023, 12:18 AM
If mounting two on the firewall is a struggle, you can potentially mount one on top of the passenger footbox. The inside part is not very deep and I doubt anyone would use the space at the top of the footbox.
rich grsc
02-25-2023, 08:58 AM
Put adjustable ball regulators on the duct hoses. :rolleyes:
So, both recommendations are to plumb the coolant lines in parallel instead of series. I was concerned that running in parallel may create two compromised heating systems whereas running in series would guarantee at least one adequate heater.
Also agree there is real estate above the PS footbox that can be utilized.
mladen
02-25-2023, 10:56 AM
If by compromised you mean that they wouldn't work as well due to cooling the fluid, I think you'd need about 50 heaters working on high to achieve that :)
that was exactly my thought, the output temp of the coolant from the heater coil should be sufficiently hot to serve as an input to a second coil. Running in series is simpler and ensures sufficient volumetric flow.
phils88gt
02-26-2023, 02:55 AM
I'm not a designer of automotive heating coils but ive designed many fluid heating coils for other applications. Average fluid coil design for hot water is a 20 deg differential. You could put them in series if you wanted to. Just the second coil would output less heat per gallon flowed. It will certainly work.
CraigS
02-26-2023, 08:03 AM
I did that on mine and ran them in series. I found a small heater assembly somewhat similar to this one
https://www.vintageair.com/heater-only/
At first I mounted one over the passenger's feet and ran an air hose over to driver side. Soon found that was not enough capacity. So I bought another one and mounted it on the firewall behind the dash. Mine had 2 speed fans and I had a cable operated valve out in the engine bay. Never hooked the valve up though. Since this is 100% recirculated air there is no flow w/o the fan. So we each had 3 options for heat; none, low fan, high fan. I opened the water valve in Sept and closed it in April. It worked well enough considering what we were driving. For about 12 years we had a New Years day Capitol Area Cobra Club cruise and we were one of two cars that were comfortable.
egchewy79
02-26-2023, 08:32 AM
Agree w/ Rich on this one. Why not put an adjustable vent on the PS?
David Williamson
02-26-2023, 09:35 AM
your experience may be different but I found the heater did nothing on the highway. If you put your hand under the dash there was some heat but that was it, so when it stopped working years ago I never fixed it. I do use the fan to help defrost the windshield when the roof is on. My wife travels with a hat and mitts beside the seat and there is a blanket in the trunk. She will wear a warm coat while I have a thin one on. And I have a 12V plug in heated seat in the trunk as well. She is comfortable.
David W
Alan_C
02-26-2023, 07:00 PM
Adjustable vents aa well as add seat heaters in both the bottom and back cushions. The FFR heater directs the heat into the foot wells and works. Once the heated air gets mixed with the turbulent air in the cockpit, the heat is gone. Other than the legs, seat heaters would do more to apply heat to one's bottom and back more effectively than a conventional heater ever could. This is the same problem as those who want AC in a roadster. Unless you are going to enclose the cabin, both heat and AC to the mid to upper body is pretty much futile.
CraigS
03-03-2023, 07:47 AM
I ran my heaters in series. I ran the hoses so the passenger side got the coolant first. Can't say I ever checked it for temp variation but, if there was any, my wife got the benefit so that worked fine. Also when I was by myself, I didn't flip her fan on so I got all of the heat.
I ran my heaters in series. I ran the hoses so the passenger side got the coolant first. Can't say I ever checked it for temp variation but, if there was any, my wife got the benefit so that worked fine. Also when I was by myself, I didn't flip her fan on so I got all of the heat.
This is exactly what I was thinking.
rthomas98
03-03-2023, 08:58 AM
You could also have your wife pick out a riding outfit from here. :D
https://www.thewarmingstore.com/heatedclothing.html
My wife complained about her feet being cold. She got some of the socks and the complaint is now gone. Just a thought given how much heat is going to be lost when you are driving at speed.
BradCraig
03-03-2023, 09:10 AM
Good luck engineering around the cooling\heating needs of the fairer sex in an open car. I as well as most folks have found that the wife ends up in the car far less than you think. Just my $.02. :-)
ydousurf
03-03-2023, 10:38 AM
Put adjustable ball regulators on the duct hoses. :rolleyes:
I think Rich has the optimal and a quick solution to the problem!?
You could always go with a different vendor/solution and then use the defrosters selection and route those hoses to the appropriate locations that you desire. Just throwing out that idea instead of using dual cores.
Doug
Mustang Man
03-04-2023, 10:01 AM
While I'm in Florida, and our driving season is opposite most other states, we do get some high 30s low 40s in our driving season. All I have is seat heaters and the wife has never complained. We wear extra layers so that as it warms up during the day we can remove an inner long sleeve shirt or even take our jackets off for the afternoon ride home. Seat heaters keep your back, bottom, and thighs warm no matter the speed. A water-based heater will lose all efficiency once you're up to speed and cockpit air is diluted with turbulent outside air. Maybe if you had a top on the car, but otherwise, after 16 years I do not regret not installing a water-based heating system one bit. Keep it simple. Wear warm clothes and use seat heaters. You'll be good for most cold weather driving.
HTH...
Mark
CraigS
03-05-2023, 08:07 AM
Good luck engineering around the cooling\heating needs of the fairer sex in an open car. I as well as most folks have found that the wife ends up in the car far less than you think. Just my $.02. :-)
This is true. That is why I did everything I could to make it comfortable for her. Take the FFR to lunch on Saturday when it is 50deg? If she isn't happy we take the daily driver. If she can hack it we take the FFR. Well worth it to me.