# Easy heater core install VW Passat



## etischer (Jun 16, 2008)

I chose a slightly different approach to installing a heater in my car. Most people replace the heater core with an electrical equivalent. The heater core is burried inside the dash on most cars, and it is generally an 8 hour job to replace it. This would be a maintance nightmare, so I found a more acessable location inside the air filter box. 






















Air filter rain cover removed.












Air filter housing removed.












Electric heater core removed from a $20 portable heater.













Electric heater core installed. 












View from inside the blower housing (blower fan removed)

Quite a nice fit, I was able to bolt the two pieces together without modifications!

The heater draws 5A at 320VDC, about 1600 watts. Air comming out of the vents is around 90 degrees when the ambient air is 60 degrees. Not as powerful as a regular car heater, but it gets hot immediately. I am using the original heaters safety thermostat. I don't know if how well it may work at twice the voltage (and half the current). It is a purely resistive load, so hopefully the contacts will not weld themselves. I also plan to use a click thermostat to power my main heater relay, in addition to the fan power.


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## Woodsmith (Jun 5, 2008)

Good mod there. Looks easy to install and access for service.

My only concern would be passing heated air over the fan. The fan normally only sees ambient air temperature and supplying heated air may cause over heating problems with the fan, and motor, if it is in the airstream.

However, if it causes you no problems then I may do likewise on my daily ICE car. Only this morning I was thinking how nice it would be to be able to demist immediately rather then 3 miles along the motorway.


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## tj4fa (May 25, 2008)

It does look a nice install.  

Hopefully, none of the plastic parts will get too hot and melt.


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## etischer (Jun 16, 2008)

Guess I'll find out =)
The core doesn't get too hot, I scanned it with a non-contact thermometer and it was around 100 degrees F on the inlet side. Everything just seems to get warm, nothing is getting hot. My only worry is the heater getting stuck on. 

The contactor Im using has aux NC contacts, so I will use these to make sure the contacts are not welded before I energize the coil. Im also swtiching the (+) and (-) for redundancy and complete isolation when the heater is off. 




tj4fa said:


> It does look a nice install.
> 
> Hopefully, none of the plastic parts will get too hot and melt.


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## tj4fa (May 25, 2008)

etischer said:


> Guess I'll find out =)
> The core doesn't get too hot, I scanned it with a non-contact thermometer and it was around 100 degrees F on the inlet side. Everything just seems to get warm, nothing is getting hot. My only worry is the heater getting stuck on.
> 
> The contactor Im using has aux NC contacts, so I will use these to make sure the contacts are not welded before I energize the coil. Im also swtiching the (+) and (-) for redundancy and complete isolation when the heater is off.


Is that something like they did on this one?

http://www.evconvert.com/eve/bring-on-the-heat


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## etischer (Jun 16, 2008)

tj4fa said:


> Is that something like they did on this one?
> 
> http://www.evconvert.com/eve/bring-on-the-heat


Yep, same circuit, execpt my contactor has an output which tells me it is fully open (no welded contacts). I will monitor this "healthy" signal before allowing the contactor to close. 

This may be overkill since the load is purely resistive. Im not sure it's worth the extra cost of a safety relay, but it's something worth thinking about. The heater being stuck on could burn the car down.


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## Overlander23 (Jun 15, 2009)

320v through a heater that's normally used in a 110v application? I was wondering about this. So it's working fine? I'll be installing a ceramic element on 200v system, and wasn't sure if it would work properly. 

Looks like 1500 watt rated elements are 1500 watts regardless of voltage, since your amp draw is pretty low.


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## Tesseract (Sep 27, 2008)

Overlander23 said:


> 320v through a heater that's normally used in a 110v application?
> ...
> Looks like 1500 watt rated elements are 1500 watts regardless of voltage, since your amp draw is pretty low.


Gah!?! No, this is a fire waiting to happen. Electric heaters invariably use a resistive element, so Ohm's law most definitely applies!

The peak to peak voltage of the 120V ac line in the US is ~320V, but the RMS voltage - _which, btw, is the equivalent voltage in DC that would heat a resistor up the same amount _- is simply 120V. 

Applying 320VDC to a 120VAC heater will result in ~7x more wattage. Hopefully the element will open soon afterward, rather than catch something on fire.

Furthermore, almost all common contactors and relays are rated to switch AC, not DC. If a DC rating is specified at all it will invariably be for a much lower voltage and/or amperage compared to the AC rating. The reason why is that AC (in the US) crosses zero volts 120 times per second so arcs are (usually) self-extinguishing. DC is, well, DC, so arcs don't extinguish once formed unless the contacts are separated by the maximum ionization distance (IIRC, that is 1kV/cm at STP*).

Rather than veer off into a didactic/pedantic explanation, just ask Dimitri about what happens if you use a regular hot water heater thermostat, rated for at least 240VAC/30A, to switch ~132VDC to a resistive heater 

etischer, you should share some more details with your setup because your results are most unusual. Did you actually measure the amount of DC current flowing through that heating element (nice installation btw)?

EDIT - I looked at your (etischer's) pics again and it appears there are multiple elements in the heater and you were able to rewire them from parallel to series - is that correct?


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## etischer (Jun 16, 2008)

The ceramic heater has 4 heating elements. Two are powered for low power, and all 4 are powered for high power. 

I doubled the voltage, but I connected the two groups of heating elements in series, so the power should remain the same. One could run 480 with all the four elements in series.

I hooked up my meter and measured 5.5 amps. If I reduced the fan speed, the ceramic heater gets hotter and current is reduced to 5 amps. It's resistance increases with temperature so in a sense it is self regulating. 

This was all done with 230V AC, I still need to finish the contactor wiring and fusing to connect to my battery pack. I don't imagine the power should change much, 230VAC should have the same rms power as 325VDC. 

Thanks for the advice on the contactor. I'll have to check the cut sheet to see what the DC ratings are. 

For non-inductive loads (AC-1) it is rated 500v 16A. I don't know what the other ratings mean.










Here's a picture of my contactor, I have an extension cord plugged in the line side of the contactor for testing.


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## tj4fa (May 25, 2008)

This may be the cut sheet based on the A600 and Q600 markings on the controller.

But don't ask me anything about this stuff. I just know how to Google.

http://database.ul.com/cgi-bin/XYV/...n=versionless&parent_id=1073990247&sequence=1





etischer said:


> Thanks for the advice on the contactor. I'll have to check the cut sheet to see what the DC ratings are.
> 
> 
> 
> ...


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## etischer (Jun 16, 2008)

I couldn't find data for the contactor I'm using, but I'm pretty sure it is a rebranded Sprecher Schuh. 

TCat is right, the ratings go to almost nothing for DC. 

These two contactors shown below are rated for 9A and 12A inductive load, 20A non inductive load. 

At 440VDC they are rated only 100mA! Looks like I'll be switching to a kilovac relay. They must have a smaller contact gap compared to DC specific contactors. I know some have magnets near the contacts to attract the arc.


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## Tesseract (Sep 27, 2008)

etischer said:


> ...
> TCat is right, the ratings go to almost nothing for DC.
> ...
> At 440VDC they are rated only 100mA! Looks like I'll be switching to a kilovac relay. They must have a smaller contact gap compared to DC specific contactors. I know some have magnets near the contacts to attract the arc.


 
TCat, huh? Hmm... that's a new one.

You could try wiring all three phases on the contactor in series to get a better interrupt rating. It still won't be enough to switch 5A at ~300VDC but it'll get you at least halfway there. If you aren't using the contactor to cycle the heater to maintain temperature then the life should be acceptable (at least 1,000 cycles would be my W.A.G.).

You could otherwise try to find a solid state relay with high voltage DC rated outputs. While these are becoming more and more common because of solar panels they are still relatively rare.

Oh, and that was an interesting tidbit about the heaters having a strong positive tempco so they self-regulate. Good to know.


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## gdirwin (Apr 7, 2009)

etischer said:


> This was all done with 230V AC, I still need to finish the contactor wiring and fusing to connect to my battery pack. I don't imagine the power should change much, 230VAC should have the same rms power as 325VDC.


230VAC is already rms so you cannot use the root(2) multiplier to get peak. From a heating/energy perspective, 230VAC would be equivalent to 230VDC (assuming unity power factor, ie a perfectly resistive load). With 325VDC, the equivalent wattage would be (325/230)*(325/230) which is almost double (assuming a constant resistive load). This should be a big concern!

I am in the same boat (see thread here: http://www.diyelectriccar.com/forums/showthread.php/ceramic-heater-and-160vdci-38696.html ) - I am using 160VDC and hoping to use 120 V ceramic heater elements (1.8 times the wattage).


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## matspassat (Sep 30, 2015)

My question may be obvious--how are you going to get enough voltage to operate that heater while driving your car? If you try to convert 12 volts to what it require, the amperage would be so high as to burn out your wiring, not to mention your alternator. You could heat up your car before driving, but that wouldn't stay warm long.


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## samwichse (Jan 28, 2012)

matspassat said:


> My question may be obvious--how are you going to get enough voltage to operate that heater while driving your car? If you try to convert 12 volts to what it require, the amperage would be so high as to burn out your wiring, not to mention your alternator. You could heat up your car before driving, but that wouldn't stay warm long.


You registered on this forum to come ask THIS question? Did you even try to read any of the thread?


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## matspassat (Sep 30, 2015)

Yes, I read the whole thread. Nowhere did I see this question answered. I saw lots of discussion about power factor, etc, but nothing about how you would get enough power from 12 volts. I found this thread in Passat World. Is your car an EV? If so, I apologize. I just assumed it was a standard Passat. If you have converted it to an EV, then you would have enough voltage, I expect your batteries would be drained quicker with the heater on, though.


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