# Cab Heater Poll - What works?



## nicklogan (Feb 4, 2010)

With winter fast approaching I've started working on a better personal warmth solution for my EV ( last year a heavy parka kept me warm but doesn't keep the windshield clear). I had planned on using a ceramic heating element but am now also considering using the existing heater core with a water heating element setup instead.
I'd like to do an informal poll and hear from people who have implemented a heating solution that works. Please include the following information if you respond:
What's the typical midwinter temperature where you live?
Do you preheat before you drive?
How long is your typical trip and does the cab stay warm enough so you don't need gloves?
Can you keep the windshield frost free and will it melt it clear in sleeting conditions?
Lastly, please provide some details on the type of system used: water heater, ceramic element, kit from an EV parts supplier, original equipment,etc. If you're satisfied with the results and live where a real winter occurs, please share. I think a lot of builders could benefit from real world feedback.

Thanks in advance,
John Nicholson
www.evalbum.com/2672


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## bluefxstc (Dec 29, 2007)

John
I use a fluid heater which I made from some pipe fittings, water heater elements and a Bosch pump. The pump was $70 and the rest of the parts cost about $20-30. Heater is about 1600w and heats the air to about 85f in 3-5 minutes. I like it because I didn’t have to modify any of the rest of the heating system. If I had to do it over, and I still might modify it, I would make it slightly bigger to heat the air to a hotter temp quicker. Say something around 2000-2500w. I live in Boise ID so typical winter temps are in the 5-30f range. My normal commute is only about 20 minutes so in the morning it is good since it has been in a garage all night, but in the afternoon after being cold soaked all day, it is takes awhile to warm up. It would be easy to do, just add another heating element but otherwise I am happy. 
Bluefxstc
http://www.diyelectriccar.com/garage/cars/242


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## EVfun (Mar 14, 2010)

I recommend 2 ceramic heaters, between 1200 and 1500 watts each. It is best to operate them in 2 stages, in a striped arrangement (every other row in each heater on when the heater is on low.) A single element suffers a little when it gets down to freezing outside. The split control allows mild heating for defrosting when you really don't want to add heat. Since it mixes half unheated air with half heated air it gives gentle amount of heat while moving a lot of air. I did not set up any preheat system. Just ceramic heat alone is already better than the ICE car heating system it replaced, the heat is much faster than waiting for an engine to heat a gallon of water.


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## tomofreno (Mar 3, 2009)

What's the typical midwinter temperature where you live?
>>> High's in the 20's F to 40's F, lows 0 F to upper 20's F, mid-20's most common.

Do you preheat before you drive?
>>> Sometimes

How long is your typical trip and does the cab stay warm enough so you don't need gloves?
>>>Anywhere from 4 to 30 miles one way. Yes.

Can you keep the windshield frost free and will it melt it clear in sleeting conditions?
>>> Yes and Yes

Lastly, please provide some details on the type of system used: 
>>> Two 1.5kW ceramic heater elements side-by-side in place of the original heater core, connected in parallel to my nominal 115V pack (cost $18.00 each). Measured V*I to them is around 3.1 kW.
Downside: had to remove the dash to install.
Upside: almost instant heat, and good airflow with two side-by-side (important). No fluids to worry about.

I usually only leave it on for about 10 minutes or less, then cycle it on/off as it gets too hot after that unless it is colder than normal. Below 10 F I leave it on most of the time. Also needs to be on more at higher vehicle speeds as the car cools faster with more airflow over it. Driving at 60 mph requires significantly more heating than driving at 35 mph. I am not certain it could keep the car warm at 60 mph in zero F temp.


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## [email protected] (Jun 14, 2011)

I have a link for an electric water heater 

I am considering trying it with a 1500 watt DC to AC converter

http://www.northerntool.com/shop/tools/product_200339137_200339137

Northern Tool and Equipment has for $39.00

*Kat's 1500 Watt Circulating Tank Heater — Model# 13150*


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## gojo (Feb 1, 2011)

I took out my old blower and heater core,and I only left the vents to the windshield in place. I then attached a ceramic hair dryer ($20) to the vents. My biggest expense was the relay switch ($98 but cheaper on ebay). The 120 volt ac hair dryer's fan works with my 120 volt dc pack. It's cheap and simple.

I am in Minnesota, and we can go down to -35F. so I only use my EV 8 months out of the year. I only use this for light frost, or condensation on the windshield, but it does warm the cab in my RX7 a bit. The other 4 months I make good use of my ICE's waste heat.


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## nicklogan (Feb 4, 2010)

Thanks for all the information. I'm going to give the water heater approach a try, similar to what bluefxstc did. Right now the plan is to use a TopsFlo 15PV solar hot water pump along with the temp sensor circuit described here ( http://www.siliconchip.com.au/cms/A_30610/article.html ) to turn the motor on and off. The first pass at the pipe assembly with a 220v/4500W element is pictured below ($60 of Home Depot parts). If 4500W is too much, it won't be too hard to change out the element. At my pack voltage it should be more like 3 KW. I'm also considering an expansion tank like the picture attached so the system will have a convenient fill point. I'll probably build a foam board box around it. If I get this together and it works ok, I'll post a parts list. I was reluctant to tear into the dashboard and not wild about bringing full pack voltage into the cab.


http://www.amazon.com/gp/product/B005EU7ONMhttp://www.amazon.com/gp/product/B005EU7ONM


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## bluefxstc (Dec 29, 2007)

Nicklogan

I found I really don’t need a temp control. On my car I use the AC on/off relay to control a mercury contactor like this. http://www.surplussales.com/Relays/mercury_con.html. The contactor controls the pack voltage. I did put a normally closed temperature control device in the circuit like this. http://www.surplussales.com/Thermal/pdf/6700.pdf In my situation I used a switch that opened up if the temperature rose above 190F. The switch is mounted on a tab I welded to the pipe and is in series with the power to the mercury contactor . If the temp goes above 190 the temp switch opens and cuts off power to the contactor and the heater. I can turn off the heater just by switching the AC switch built into my car to off. If I had to do it again I would not use the temp switch since I haven’t found that the water gets above 100f-110f. It works well without it and I prefer simple to complicate. Additionally, my car adjusts the temp by mixing outside air with heated air and that still works so I can control the temp that way. For an expansion tank I used the stock expansion tank in the stock location. It made mounting easy. What size are your barb fittings? I sized mine so they were the same size as the stock heater hose. Yours look a little small but it may just be the picture. I used a bosch aux water pump from a Mercedes. It was $70 at a local auto parts store. Need to be careful that you are able to bleed all the air out of the system. I have a small fitting at the top of my system to accomplish this. It is normally closed but when I filled the system I had it open. I also had to have my pump at the bottom of the system to make sure it always had fluid. It did take a while to get it working. Let me know if you have any questions. 

Bluefxstc


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## GizmoEV (Nov 28, 2009)

Maybe someone else can confirm but I would be leery of using galvanized pipe in the heating system. I'm sure there is a reason other than cost that it isn't used by OEMs in any vehicle I have seen. If you don't want to use something difficult then why not some CPVC hot water pipe that you can glue together?


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## nicklogan (Feb 4, 2010)

bluefxstc
"On my car I use the AC on/off relay to control a mercury contactor like this. http://www.surplussales.com/Relays/mercury_con.html. The contactor controls the pack voltage. I did put a normally closed temperature control device in the circuit like this. http://www.surplussales.com/Thermal/pdf/6700.pdf "

Those mercury contacts look good, I'll consider those but I already have an Allbright SW60B built into my motor contoller box from when I was planning on using ceramic heater elements. I wanted to use that temp control circuit to control the pump to save wear on the contactor (even though it has magnetic blowouts and an arc suppresion diode). I don't have AC (it's an '84 truck) but I'll likely use that bimetallic snap switch as an overtemp safety on the contactor with a dash mounted on-off switch. It remains to be seen if the motor control circuit and heater core fan speed switch will work ok to regulate temperature in the cabin. I think my heater element wattage is higher than yours so I may have to downsize.

 "I used a bosch aux water pump from a Mercedes. It was $70 at a local auto parts store."

I looked at those but they seemed to be used in auxilary situations (heater circulation with the motor off and turbo cooling) so I was concerned about lifetime. The solar pump is rated for 30,000 hours and has a soft start. It was about $70 also. It's not rated as highly as a Laing D5 solar pump (probably with good reason but time will tell) but those are also three times the price. EVsource uses a Laing in their hot water heater kits.

Thanks for the tips.

GizmoEV
"Maybe someone else can confirm but I would be leery of using galvanized pipe in the heating system. I'm sure there is a reason other than cost that it isn't used by OEMs in any vehicle I have seen. If you don't want to use something difficult then why not some CPVC hot water pipe that you can glue together? "

I'm not sure I understand why you would be concerned about pipe thats used primarily for hot water and steam heating systems. It's heavier and more expensive than plastic pipe so OEM's may avoid it for those reasons. It was all pre-cut and threaded, so not difficult at all to put together right off the shelf. I would rather not have to smell the toluene in plastic pipe glue. It also means I have to worry less about a "meltdown" event or fire. If you want to use plastic pipe I suppose a spa heater unit would work but it would cost quite a bit more.

I'll let people know how (or if) it works out.


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## nicklogan (Feb 4, 2010)

bluefxstc

"For an expansion tank I used the stock expansion tank in the stock location. It made mounting easy. What size are your barb fittings? I sized mine so they were the same size as the stock heater hose."

I forgot to answer your question - the barb fittings are 1/2" for the ones going to the heater core fittings and 3/8" for the one going to the expansion tank. The original tank was odd shaped and old and the new one will fit better in the insulated box with the heater unit. It also will take a standard pressure relief radiator cap.


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## tomofreno (Mar 3, 2009)

> The first pass at the pipe assembly with a 220v/4500W element is pictured below ($60 of Home Depot parts). If 4500W is too much, it won't be too hard to change out the element. At my pack voltage it should be more like 3 KW


4500W at 220V rms would be a heater resistance of 220*220/4500 = 10.76 Ohm, so at 144V I would expect about 144*144/10.76 = 1927W, and of course less while driving if the lead acid pack voltage sags significantly in winter under load.


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## tomofreno (Mar 3, 2009)

There are several other posts here from people who used galvanized pipe with a water heater in the past. I've not seen anyone report any problems. Of course it and the pump and lines will need to be insulated well to limit heat loss outside the cab.


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## GizmoEV (Nov 28, 2009)

nicklogan said:


> I'm not sure I understand why you would be concerned about pipe thats used primarily for hot water and steam heating systems.


I didn't know if electrolysis would be a problem. You will have several different metals in the same fluid. There is a reason that hot water attachment pipes have a plastic insulator between the copper tubing and the steel swivel nut that attaches to the galvanized hot water tank. Maybe there won't be any issue with the brass fittings in the galvanized pipe. I just wasn't sure and thought you might want to find out. From what Tomofreno says he hasn't heard of any one reporting problems. Of course if they don't inspect inside the tubing they won't know until something lets loose.


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## nicklogan (Feb 4, 2010)

tomofreno
"4500W at 220V rms would be a heater resistance of 220*220/4500 = 10.76 Ohm, so at 144V I would expect about 144*144/10.76 = 1927W, and of course less while driving if the lead acid pack voltage sags significantly in winter under load."

Right, that estimate off the top of my head was high. And actually it's a 240 volt element so 4500W/240V = 18.75A, 240V/18.75 = 12.8 ohms, 144v/12.8 ohms = 11.25A, 144V x 11.25A = 1620W. Downsizing may not be the concern.

"There are several other posts here from people who used galvanized pipe with a water heater in the past. I've not seen anyone report any problems. Of course it and the pump and lines will need to be insulated well to limit heat loss outside the cab. "

Right. And people have been using brass radiators with iron engine blocks for over a hundred years (but not so much lately!). Additives in modern antifreezes should take care of the problem of electrolysis. The foam box and line insulation should confine heat loss to where it's wanted.


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## GizmoEV (Nov 28, 2009)

nicklogan said:


> And people have been using brass radiators with iron engine blocks for over a hundred years (but not so much lately!). Additives in modern antifreezes should take care of the problem of electrolysis. The foam box and line insulation should confine heat loss to where it's wanted.


I've never seen a brass radiator. I've only seen copper and aluminum ones. It is probably the (fortunate) lack of modern antifreeze in household water that necessitates the special insulating couplings on home waterheaters.


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## Roderick (Dec 8, 2013)

I think choosing between ceramic and water heating choices are just as simple as, do you want spend time on installing or spend time on waiting for heat.
I believe ceramic heating is cheaper and more efficient (efficient as in less energy spent to produce the same temperature inside the cabin)

am I wrong?


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## gojo (Feb 1, 2011)

Roderick said:


> I think choosing between ceramic and water heating choices are just as simple as, do you want spend time on installing or spend time on waiting for heat.
> I believe ceramic heating is cheaper and more efficient (efficient as in less energy spent to produce the same temperature inside the cabin)
> 
> am I wrong?


I agree with you, having gone with a ceramic hair dryer for heat. It is simple and also less weight involved. I removed all the old heating fans, and such, and simply put in the hair dryer. I am running on 120 volts DC, and to my surprise the 120 volt AC fan motor still worked. I needed to buy relay switch.

I would only recommend this for mildly cold weather.


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## poprock (Apr 29, 2010)

A 2 speed 12v caravan hair dryer gives an embarrassing amount of heat on the high setting and is easily fixed into the demister venting. I fitted a micro switch to the heat lever operating a 12v 40 amp relay.


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## Moltenmetal (Mar 20, 2014)

I too am using a 120VAC compact (travel) hairdryer, connected to the defrost duct hose on my Spitfire with a rubber Fernco coupling, and a relay capable of stopping a DC arc to turn it on and off- that's critically important. The relay I tried to use originally, rated for 230 VAC and 40 A, wasn't able to stop the arc and it melted the first time I tested it. 

Note that the high/low/off sliding switch, as well as the thermoswitch and thermal fuse installed in that hairdryer to protect against the fan stopping - none of these are good for DC. If the fan stops you need to shut it off immediately or you're going to possibly have a fire under your dash. I removed them all. Since I use mine only for windshield defogging and then only rarely (it's a convertible), and nobody drives the car but me EVER, it's not a huge risk to me.

The hairdryer is a nichrome resistance wire type, with a little DC motor which runs the fan. It uses a parallel connection off part of the nichrome wire coil to get a low enough voltage for the motor, and a diode to convert the AC to DC. If you get the polarity right, it runs just fine directly from my 105VDC pack.

I don't drive the car in the winter. From what I've read here, you're looking for at least 2500 watts of heating in that case in a typical car to be at all comfortable.

The ceramic space heaters that I've seen all have shaded pole AC motors, so they require some Frankensteining to use. You need a DC blower or fan (generally the 12V ones are your best option here). If your heater core is amenable to swapping out the water-to-air heat exchanger with a couple of these ceramic elements in the correct geometry, then that's an approach that several people here have used successfully.

Irrespective of whether you're using air or water heating, a reliable means to shut off the DC supply to the heater is essential. A means to shut off that power when the temperature goes too high (because of a fan failure) is also a very good idea- one I haven't implemented yet in mine, but if this were a car other people were going to drive I would definitely do it for safety. But also be aware that relay contacts can stick or weld together, and solid state relays can fail in the fully on state. Generally, heater circuits require a second, independent means of shutoff in case that happens- that's what the thermoswitch and/or thermal fuse is for. You can probably safely put the AC rated thermoswitch and thermal fuse in your heater device in series with the coil of your DC relay (obviously removing them from the AC circuit they're wired into now!) and then the only thing you need to worry about is the contacts of your relay welding together.

The ceramic elements are somewhat self-regulating, but not reliably enough to be failsafe against a fan failure. All the ceramic heaters I've taken apart have at least one secondary safety against fan failure.

If you're using water heating, similarly you need a means to protect against excessive pressure due to boiling if your pump fails. Your element should be protected against boiling dry- a short circuit of your pack voltage to the chassis of your car resulting from a failed heater element is likely not something you want either. Your pump needs to be good for hot water (most of the little DC pumps aren't). 

As to the worries about galvanized parts and galvanic corrosion, here's the piece of information you're missing. A car's cooling system is FULL of dissimilar metals. The reason you can get away with that and not experience enormous galvanic corrosion of the less-noble parts is a) it's a closed system which has a minimal ingress of fresh oxygen, and b) the antifreeze mixtures are loaded with corrosion inhibitors. The steel pipes, brass valves and cast iron radiators of my house's 80+ yr old hydronic heating system are in perfect condition on the interior just because it's a closed system with minimal fresh oxygen being admitted. As to the zinc galvanizing: don't worry about it. It won't help much, but it won't hurt either. Just make sure your system has an expansion tank (water expands as it heats up, just like everything) and that the tank is sealed against fresh air entrance but also has a means to relieve pressure if you start making steam. A tube off the top of your expansion tank running into another bottle partially filled with antifreeze will do that job nicely- it will vent excess pressure while also preventing too much air from being sucked back into the system every time it cools down again.


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