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zoti
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Joined: December 26, 2007
Posts: 2064
Location: Plano, TX USA
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 Posted: Sat Oct 29, 2022 11:12 pm Post subject: Re: Installing Bobilvan's CDH water heater |
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I would add another flap to the hot air hose after the heat exchanger to divert the hot air back into the cabin or outside to vent.
This way you get a hot shower and hot air while you are showering. |
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fxr
Samba Member
Joined: December 07, 2014
Posts: 2325
Location: Bay area CA
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| Posted: Sun Oct 30, 2022 10:37 am Post subject: Re: Installing Bobilvan's CDH water heater |
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| zoti wrote: |
I would add another flap to the hot air hose after the heat exchanger to divert the hot air back into the cabin or outside to vent.
This way you get a hot shower and hot air while you are showering. |
It's actually not that warm by the time it's been through the exchanger - and if you want cabin heat as well while heating the water (we well might) just put the flap to a quarter open to the cabin - that makes the airflow about half through the exchanger with its extra inherent drag.
Plus (with the afterburner) the heater switches off when the water is hot enough, so when actually showering you have turn it back on again if it wasn't on before you started heating water. That last bit sounds complicated - but the GPIO input to the afterburner just switches the heater to Maxpwr (maximum power) from whatever it was before and when disconnected the heater goes back to its previous setting. 
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Jim Crowther
1984 1.9l EJ22 Westy Wolfsburg Edition
Vespa GTS 300 |
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fxr
Samba Member
Joined: December 07, 2014
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Location: Bay area CA
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ledogboy 
Samba Member
Joined: September 19, 2005
Posts: 578
Location: Scappoose, OR / Oakland, CA
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| Posted: Sun Nov 06, 2022 3:22 pm Post subject: Re: Installing Bobilvan's CDH water heater |
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| fxr wrote: |
| I've just finished adding a servo to control the diverter valve instead of the extremely unwieldy 'choke' cable provided.] |
That is really cool and seriously impressive. Kudos!
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1986 Westy Weekender
Now a full camper
1.8t Syncro conversion
Some people call him Maurice... |
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shagginwagon83
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Joined: February 07, 2016
Posts: 3805
Location: VA/TN
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| Posted: Mon Nov 07, 2022 6:17 am Post subject: Re: Installing Bobilvan's CDH water heater |
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Oh man this is awesome!!
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Brandon
"Jo Ann" - '83.5 Westfalia EJ22e w/Peloquin
Instagram @joannthevan |
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jimf909
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Joined: April 03, 2014
Posts: 7482
Location: WA/ID
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| Posted: Mon Nov 07, 2022 7:27 am Post subject: Re: Installing Bobilvan's CDH water heater |
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| fxr wrote: |
1. The Bowden cable... |
Bowden cable? You mean the thing I've been working with since I was adjusting the brakes on my Huffy nearly 50 years ago? All these years I just called it a brake cable or derailleur cable or tencentlife fresh air cable. It turns out it has a name and an intriguing story behind the name: Bowden at then corporate giant (  ) Raleigh Bicycles? Bowden, small-time inventor who died at a young 44 years old? George Larkin, Bowden employee?
https://en.wikipedia.org/wiki/Bowden_cable
A 1918 Lewis gun on a Foster mounting fitted to an Avro 504K Night Fighter. The gun trigger is operated by a Bowden cable
Thanks for the thread and the name behind the cable.
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- Jim
| Abscate wrote: |
Do not get killed, do not kill others.
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Current: 1990 Westy Camper - Bostig RG4, 2wd, manual trans w/Peloquin, NAHT high-top, 280 ah LFP battery, 160 watts solar, Flash Silver, seam rust, bondo, etc., etc.
Past: 1985 Westy Camper - 1.9 wbx, 2wd, manual trans, Merian Brown, (sold after 17 years to Northwesty who converted it to a Syncro). |
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syncrodemaya
Samba Member
Joined: February 24, 2017
Posts: 106
Location: Vancouver
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| Posted: Wed Mar 13, 2024 3:57 pm Post subject: Re: Installing Bobilvan's CDH water heater |
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| fxr wrote: |
| zoti wrote: |
I would add another flap to the hot air hose after the heat exchanger to divert the hot air back into the cabin or outside to vent.
This way you get a hot shower and hot air while you are showering. |
It's actually not that warm by the time it's been through the exchanger - and if you want cabin heat as well while heating the water (we well might) just put the flap to a quarter open to the cabin - that makes the airflow about half through the exchanger with its extra inherent drag.
Plus (with the afterburner) the heater switches off when the water is hot enough, so when actually showering you have turn it back on again if it wasn't on before you started heating water. That last bit sounds complicated - but the GPIO input to the afterburner just switches the heater to Maxpwr (maximum power) from whatever it was before and when disconnected the heater goes back to its previous setting. |
Why did you run the airflow from the heat exchanger to the outside of the van? Seems like an unnecessary hole to cut into the body.
Did you add an expansion tank into the closed system? I'm thinking the heat into that closed loop will create some pressure after a while.
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'88 Sunroof Syncro 2.1L |
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fxr
Samba Member
Joined: December 07, 2014
Posts: 2325
Location: Bay area CA
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| Posted: Wed Mar 13, 2024 5:23 pm Post subject: Re: Installing Bobilvan's CDH water heater |
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| syncrodemaya wrote: |
| fxr wrote: |
| zoti wrote: |
I would add another flap to the hot air hose after the heat exchanger to divert the hot air back into the cabin or outside to vent.
This way you get a hot shower and hot air while you are showering. |
It's actually not that warm by the time it's been through the exchanger - and if you want cabin heat as well while heating the water (we well might) just put the flap to a quarter open to the cabin - that makes the airflow about half through the exchanger with its extra inherent drag.
Plus (with the afterburner) the heater switches off when the water is hot enough, so when actually showering you have turn it back on again if it wasn't on before you started heating water. That last bit sounds complicated - but the GPIO input to the afterburner just switches the heater to Maxpwr (maximum power) from whatever it was before and when disconnected the heater goes back to its previous setting. |
Why did you run the airflow from the heat exchanger to the outside of the van? Seems like an unnecessary hole to cut into the body. |
When I installed this, I didn't realise the air would be warm at best - if I was re-doing it in another van I'd certainly consider venting that air inside. A good point. 
| Quote: |
Did you add an expansion tank into the closed system? I'm thinking the heat into that closed loop will create some pressure after a while. |
The hot water tank has an overflow vent - this takes care of any expansion.
I'm just re-doing the electrics for this, to simplify them. When putting this together, I installed a switch at every point where I might want to have control for some reason - most of those have proved unnecessary, but confusing for Mrs fxr...
One thing I want to automate is the servo control of the air diverter valve. This is trickier than it might at first appear. It might just have to be left as one of those things that have to be remembered each time. Which means it'll always be forgotten, cueing much cursing later...
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Jim Crowther
1984 1.9l EJ22 Westy Wolfsburg Edition
Vespa GTS 300 |
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syncrodemaya
Samba Member
Joined: February 24, 2017
Posts: 106
Location: Vancouver
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| Posted: Wed Mar 13, 2024 8:22 pm Post subject: Re: Installing Bobilvan's CDH water heater |
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That's great to hear there is an overflow vent, thanks for that info!
Please post how the servo install goes what your method ends up being for that.
Also do you have any data for time it takes to heat up a full tank of hot water? I've watched a couple YouTube videos about them it seems like it is about 15 mins to get to 40 degrees (Celsius), curious what you have seen using this system.
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fxr
Samba Member
Joined: December 07, 2014
Posts: 2325
Location: Bay area CA
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| Posted: Thu Mar 14, 2024 10:22 am Post subject: Re: Installing Bobilvan's CDH water heater |
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| syncrodemaya wrote: |
That's great to hear there is an overflow vent, thanks for that info!
Please post how the servo install goes what your method ends up being for that.
Also do you have any data for time it takes to heat up a full tank of hot water? I've watched a couple YouTube videos about them it seems like it is about 15 mins to get to 40 degrees (Celsius), curious what you have seen using this system. |
15 minutes seems a bit optimistic - if the water starts at 20C then perhaps, but usually it starts much lower than that. Worst case has been about 25 minutes from start to 40C ready, but usually more like 20 minutes. All depends on how cold the water is, and if the CDH is already on at full blast.
The servo works fine as it is - there's a 12V to 5V regulator powered from the 'water heater on' switch. The 5V feeds a servo controller with manual control, and the servo can give the full swing of the diverter actuator. However to have that auto controlled rather than manual means having the regulator powered on all the time the CDH is on plus an added relay - I'm not sure I like that.
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Jim Crowther
1984 1.9l EJ22 Westy Wolfsburg Edition
Vespa GTS 300 |
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syncrodemaya
Samba Member
Joined: February 24, 2017
Posts: 106
Location: Vancouver
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| Posted: Thu Mar 14, 2024 2:28 pm Post subject: Re: Installing Bobilvan's CDH water heater |
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| fxr wrote: |
15 minutes seems a bit optimistic - if the water starts at 20C then perhaps, but usually it starts much lower than that. Worst case has been about 25 minutes from start to 40C ready, but usually more like 20 minutes. All depends on how cold the water is, and if the CDH is already on at full blast.
The servo works fine as it is - there's a 12V to 5V regulator powered from the 'water heater on' switch. The 5V feeds a servo controller with manual control, and the servo can give the full swing of the diverter actuator. However to have that auto controlled rather than manual means having the regulator powered on all the time the CDH is on plus an added relay - I'm not sure I like that. |
20-25 minutes is still pretty good for a full tank of hot water! I've been also looking into coolant heaters that could be used on water tanks and curious to see the efficiency of both systems and also the amount of setup involved with both. A Webasto coolant heater could be more efficient but requires more setup potentially for a fuel source as well as another exhaust port.
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'88 Sunroof Syncro 2.1L |
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fxr
Samba Member
Joined: December 07, 2014
Posts: 2325
Location: Bay area CA
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| Posted: Sat Mar 23, 2024 5:59 pm Post subject: Re: Installing Bobilvan's CDH water heater |
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| fxr wrote: |
One thing I want to automate is the servo control of the air diverter valve. This is trickier than it might at first appear. It might just have to be left as one of those things that have to be remembered each time. Which means it'll always be forgotten, cueing much cursing later... |
And now that's done.
Powered a relay from the power feed for the GPIO relay, removed the wiper connection from the servo control board potentiometer, and put the relay contacts across the pot's board connections. Now the relay simulates the pot moving from one endstop to the other, and the air diverter valve works just the way I wanted. Now it's just one switch to turn on the water heater, and it all turns off automagically when the water is up to temp. 
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Jim Crowther
1984 1.9l EJ22 Westy Wolfsburg Edition
Vespa GTS 300 |
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fxr
Samba Member
Joined: December 07, 2014
Posts: 2325
Location: Bay area CA
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| Posted: Mon Mar 25, 2024 3:57 pm Post subject: Re: Installing Bobilvan's CDH water heater |
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The above works OK, but the servo returns to 'Cabin' as soon as the heater turns off from MAXPWR. This means that hot air under maximum fan is now fed into the cabin - not desirable with the possibility of a shower curtain hanging right by the outlet. Now modified so that the servo relay coil ground is controlled from the Afterburner GPIO O/P 1, set to activate on RUN (i.e. NOT in 'Standby'). As the coil supply is fed from the water heater switch, it can only activate when the water heater is switched on AND the CDH is running, even if just cooling down.
Yes, I know, rather convoluted and only of interest to those who might be heating water this way, but it works perfectly as desired.
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Jim Crowther
1984 1.9l EJ22 Westy Wolfsburg Edition
Vespa GTS 300 |
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