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Modifying AC Kit (In Squareback)
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nogoodwithusernames
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PostPosted: Tue Jan 12, 2021 1:22 pm    Post subject: Modifying AC Kit (In Squareback) Reply with quote

Alright folks, looking to get some feedback regarding an idea of mine. I've got a Gilmore enterprises AC kit for my Squareback, and I am contemplating setting it up to run as a heat pump also. (T4 engine conversion with homemade stainless exhaust manifold so no heat currently...)

To start with I'll summarize my knowledge:

I know I'll have to source another evap valve, a couple check valves, reversing valve, and a two way drier.

The kit as it is, seems to have a thermostat dial that has a cap tube (??) running to the evaporator to control when the system need the compressor or not, as well as of course a fan control switch. (This is speculation on my part based on what I've observed so correct me if I'm wrong.)

Now for the questions.

Once I get the system setup mechanically, how do I run it??

Fan control will obviously still work, but what about switching between heat and AC? Would I need an additional thermostat to control it in heat mode or can I source something that can do heat and cold control?

I thought up some crazy contraption where two differently calibrated thermostats are connected with some 3D printed gearing system so that it's setup to seamlessly switch between the two but that seems far fetched Laughing

Also where should I source parts from?
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PostPosted: Tue Jan 12, 2021 2:21 pm    Post subject: Re: Modifying AC Kit (In Squareback) Reply with quote

Iíll say first off, that I barely know how a heat pump actually works, but I do understand the theory.
My simple mind envisions two buttons. One button to engage the A/C system and a second button that energizes whatever relays are required for reversal. Similar to the O/B terminals on a heat pump thermostat.
I canít speak to any specific temperature control. Every Heat Pump thermostat Iíve seen runs on 24V A/C.
I had an old Honda back in the day that had A/C added. It was basically on or off with different fan speeds.
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Mispeld
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PostPosted: Wed Jan 13, 2021 6:22 am    Post subject: Re: Modifying AC Kit (In Squareback) Reply with quote

Interesting topic. I often wondered about a heat pump in a car since I own two diesel cars, a diesel truck and of course my ACVW. But I live on the coast of NC so heat isn't too important to me. I was more interested in the concept.

I am no expert on vehicle AC's but I did work as a certified HVAC service technician on residential/commercial.

In residential - the reversing valve is normally operated when control voltage 24VAC to the reversing valve is turned off (some are opposite but the theory is if anything fails the unit will be on heat mode). The evaporator and condenser will both be the same but will switch jobs meaning the evap will now become the condenser and vice versa. You shouldn't need any extra coils. So to switch between AC and heat would simply be one wire energized or not to the reversing valve. You would have to make sure the reversing valve can work on 12VDC.

I would think the hard part would be to source bi-flow expansion valves to work with 134a pressures. I would want a TXV for the evaporator side but one that could be bypassed in heat mode and perhaps a piston type expansion valve for the condenser coil. I wonder how a piston would handle the RPM fluctuation/pressures/flow of the compressor?

Another area of concern would be the condenser coil icing over in heat mode. I am sure if your savvy you can install some type of timed relay to switch to AC mode to defrost the coil while the blower motor turns off. I suppose replacing a residential type defrost card with some type of mechanical relays and such?

I doubt you would need a thermostat unless your looking for a fancy climate controlled vehicle like that of a new car where you can set the temp. I have never worked on RV's, but maybe they run off of 12VDC?

The concept isn't rocket science, but is it worth it? A heat pump in any water cooled vehicle is pointless in my opinion. Could be interesting in a ACVW but I don't think the juice is worth the squeeze. I had a fastback in the 90's and that heat was great. It melted a cheap 12v plug-in compressor I had on the floor behind the drivers seat. I would rather run stock heat with no loss of HP rather than running a compressor and dogging the 1600.
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nogoodwithusernames
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PostPosted: Wed Jan 13, 2021 9:33 am    Post subject: Re: Modifying AC Kit (In Squareback) Reply with quote

Mispeld wrote:
The concept isn't rocket science, but is it worth it? A heat pump in any water cooled vehicle is pointless in my opinion. Could be interesting in a ACVW but I don't think the juice is worth the squeeze. I had a fastback in the 90's and that heat was great. It melted a cheap 12v plug-in compressor I had on the floor behind the drivers seat. I would rather run stock heat with no loss of HP rather than running a compressor and dogging the 1600.


That is exactly the question going through my head. Though a few things to point out I don't have any heat at this time so this is a cost/benefit analysis of modifying an AC kit to run heat VS. if it's easier/better to build heater boxes around my existing T4 header or source some bus heater boxes. And it's a 1.7 T4 motor so I'm not too concerned about the couple of HP I'll lose as I've already got a fair bit over the stock 1600.

I suppose finding parts that work with R134a will be the determining factor if they exist and are not stupid expensive. I suppose I'll start searching on auto part sites since anything they have will be rated for 134a.

Thanks for all the replies so far, and feel free to hop in with thoughts and opinions.
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Mike Fisher
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PostPosted: Wed Jan 13, 2021 10:36 am    Post subject: Re: Modifying AC Kit (In Squareback) Reply with quote

Easier to just put stock heater boxes on it like the Germans designed it.
Keep heating/cooling separate!
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PostPosted: Wed Jan 13, 2021 10:48 am    Post subject: Re: Modifying AC Kit (In Squareback) Reply with quote

It might make an interesting exercise in "conversion losses" as we go from chemical to pressure to inertial to phase change and back, instead of using the original waste heat to achieve the end result directly!
Wink


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PostPosted: Wed Jan 13, 2021 3:03 pm    Post subject: Re: Modifying AC Kit (In Squareback) Reply with quote

Mike Fisher wrote:
Easier to just put stock heater boxes on it like the Germans designed it.
Keep heating/cooling separate!


there you go posting without reading again...

but Derek I do think you would be better off with some custom heater boxes filled with swarf instead of going the heat pump route
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PostPosted: Wed Jan 13, 2021 3:42 pm    Post subject: Re: Modifying AC Kit (In Squareback) Reply with quote

Erik G wrote:
Mike Fisher wrote:
Easier to just put stock heater boxes on it like the Germans designed it.
Keep heating/cooling separate!


there you go posting without reading again...

but Derek I do think you would be better off with some custom heater boxes filled with swarf instead of going the heat pump route


There you go shooting off your mouth without understanding I knew he would have to modify his exhaust/heater boxes! Then agreeing with me in the end.
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PostPosted: Wed Jan 13, 2021 3:45 pm    Post subject: Re: Modifying AC Kit (In Squareback) Reply with quote

There is a thread about making custom heater boxes using steel wool or equivalent. Can't find it right now...
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nogoodwithusernames
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PostPosted: Wed Jan 13, 2021 3:53 pm    Post subject: Re: Modifying AC Kit (In Squareback) Reply with quote

Guys, guys, it's alright, you both think heater boxes are the best option eh? Let's leave it at that, enough junk in our lives as-is let's stay focused on our VW's here. Cool

I was picturing in my head painstakingly TIGging each fin onto the header pipes which would take eons, but if I can wrap in a coarse wool like stainless scrubbers... That opens up the heater box option as much more feasible. Skins would be fairly easy to fab up and then source some 914 flapper boxes and it'd about put itself together. And likely a fair bit cheaper than sourcing extra parts to convert the AC.

If anyone has a link to that thread I'd appreciate it, and I'll so some searching for it as well via google.

This is exactly the kind of feedback I was looking for. Yeah it could be a neat project to do a heat pump but I just want the easiest and cheapest heat source I can get. Cheers to you all!
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(Conversion thread https://shoptalkforums.com/viewtopic.php?f=1&t=151375&sid=f0542d44a322d290c29d6609fac7f215)
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PostPosted: Wed Jan 13, 2021 7:04 pm    Post subject: Re: Modifying AC Kit (In Squareback) Reply with quote

nogoodwithusernames wrote:
Guys, guys, it's alright, you both think heater boxes are the best option eh? Let's leave it at that, enough junk in our lives as-is let's stay focused on our VW's here. Cool

I was picturing in my head painstakingly TIGging each fin onto the header pipes which would take eons, but if I can wrap in a coarse wool like stainless scrubbers... That opens up the heater box option as much more feasible. Skins would be fairly easy to fab up and then source some 914 flapper boxes and it'd about put itself together. And likely a fair bit cheaper than sourcing extra parts to convert the AC.

If anyone has a link to that thread I'd appreciate it, and I'll so some searching for it as well via google.

This is exactly the kind of feedback I was looking for. Yeah it could be a neat project to do a heat pump but I just want the easiest and cheapest heat source I can get. Cheers to you all!


it's what people do for aircraft. that may help you find stuff not here on thesamba...
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PostPosted: Sun Jan 17, 2021 11:32 am    Post subject: Re: Modifying AC Kit (In Squareback) Reply with quote

why wood you need another evaporator?? just bypass the expansion valve.and add one to the condenser that can be bypassed could also pull some heat off the oil cooler or just use a heat exchanger. I dont see it being that hard to do. kinda like riding the vapor in reverse.....with a few extra parts. you could also make a hot water heater.just make the J tubes from stainless add some finnage and a tube around them welded & sealed good add fittings&anitfreezze&pump. you may also need a external core to run in the summer so you dont boil the liquid & cook nutten. inner cooler pump should do the trick. or....put a waterboxer engine in Shocked Wink
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PostPosted: Sun Jan 17, 2021 2:56 pm    Post subject: Re: Modifying AC Kit (In Squareback) Reply with quote

Once completed you will have a window fogging issue due to recirculating interior air to heat....add that into your thoughts
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PostPosted: Sun Jan 17, 2021 5:00 pm    Post subject: Re: Modifying AC Kit (In Squareback) Reply with quote

bring in some out side air for the heat/ac will help. ac de fogs a lot better than heat.
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PostPosted: Yesterday 10:50 am    Post subject: Re: Modifying AC Kit (In Squareback) Reply with quote

air-h2o-air wrote:
Once completed you will have a window fogging issue due to recirculating interior air to heat....add that into your thoughts


Had not thought of that, I was planning on connecting to the defrost vents too...

I think that settles for sure that I'll build some heater boxes then. At least for the time being. Maybe some day when I'm bored I'll still do it but for now I've got enough projects on my plate that I'm going to take the easier path for this one.

Though by all means keep brainstorming, perhaps I'm not the only one with a somewhat non-stock setup that wants options for heating and cooling. I am doing my best to keep it all looking stock or at least hidden away as best as possible.
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(Conversion thread https://shoptalkforums.com/viewtopic.php?f=1&t=151375&sid=f0542d44a322d290c29d6609fac7f215)
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nogoodwithusernames
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PostPosted: Yesterday 10:53 am    Post subject: Re: Modifying AC Kit (In Squareback) Reply with quote

mark tucker wrote:
why wood you need another evaporator?? just bypass the expansion valve.and add one to the condenser that can be bypassed could also pull some heat off the oil cooler or just use a heat exchanger. I dont see it being that hard to do. kinda like riding the vapor in reverse.....with a few extra parts. you could also make a hot water heater.just make the J tubes from stainless add some finnage and a tube around them welded & sealed good add fittings&anitfreezze&pump. you may also need a external core to run in the summer so you dont boil the liquid & cook nutten. inner cooler pump should do the trick. or....put a waterboxer engine in Shocked Wink


Whoops, look like I wrote that wrong. Meant that I would need another expansion valve for going the other direction, at least according to diagrams I've seen.

And no water-cooled motors for me Cool I'm enjoying the little 1.7 type 4 in it right now.

Water heater is interesting, and my exhaust is currently stainless. Though that'd be a lot of extra weight to lug around for no good reason when heater boxes would probably be plenty for me Laughing
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