Although I have made provisions for future wire runs by putting several different types of cabling along my cold air duct in the center of the floor (front to back) I find the need to make 110v runs as I did not pre install my wiring while building. Changed my mind on design too many damn times.
What I am thinking of doing is similar to the OEM by run heating ducts at the floor to wall area under a shield but to actually run the heat - a/c ducts through ABS plumbing. This way I can control the air distribution better and utilize automotive dash vent covers on the outlets to direct airflow and control the different zones.
First, I don't know if the ABS will handle the heat but seeing it used as an exhaust stack for mid to high efficiency home furnaces, I think it should work.
Secondly I need advice on also running 110 inside the same area. A little nervous on this one but again I see wiring run close to heat ducting in houses.
There is NO WAY I'd run wiring in a HEAT duct. And pretty sure it'd have to be the very last and ONLY option to even consider it in an A/C duct.
Heat and wiring don't mix as wiring already has a hard enough time not over heating just from the current loads.
The reason I wouldn't want it in an A/C duct is the condensation which is moisture which is almost as bad as heat.
;D BK ;D
Quote from: B_K on March 20, 2017, 07:38:03 AM
There is NO WAY I'd run wiring in a HEAT duct. And pretty sure it'd have to be the very last and ONLY option to even consider it in an A/C duct.
Heat and wiring don't mix as wiring already has a hard enough time not over heating just from the current loads.
The reason I wouldn't want it in an A/C duct is the condensation which is moisture which is almost as bad as heat.
;D BK ;D
Would over-sized wires in conduit satisfy both problems?
A couple of things here. You are not supposed to run low voltage and high voltage wiring together. ABS does not like hot temperatures and will melt at 175f, but don't know if your heater heat would melt it. Flexible air heater hose is easier to work with.
--Geoff
Quote from: DoubleEagle on March 20, 2017, 10:03:27 AM
Would over-sized wires in conduit satisfy both problems?
In my opinion NO.
But I'm no expert. But the way I see it just because it's in conduit doesn't take away the heat or condensation issues.
;D BK ;D
I would imagine the hot dry air would quickly dry out the plastic insulation on the wire and it would begin to crack from the flexing of the bus allowing in the humidity in the air and further speeding up corrosion. It sounds like a plan that is doomed to failure. JMHO There are other ways to add wire runs after the fact. We used to get creative all the time when updating buildings and still remain within codes.
Good luck with your project.
I have been blessed with knowing George Myers (who lives close by) who is an electrical engineer, and has authored many articles on wiring in Bus Conversions Magazine, and written his own guides. I saw how he had laid out massive amounts of plastic conduit in his own conversion that went everywhere. His advice was that if a circuit is going to be buried in insulation just under a hot roof, go to the next size so that it could carry the current despite the heat (12 gauge called for, go to 10 gauge).
As far as whether conduit can keep out moisture goes, with weather tight connections everywhere in the system, it should not gain moisture. I had a dump trailer that was used to haul road salt year-round that had conduit running to every light with sealed fittings that did a good job of keeping the salt water out. So, it seems that with the proper conduit there should be no problem running in A/C ducts if the electrical code does not have anything against it. With heating ducts, it would depend on how hot they actually get. We should probably go by what might be said about all of this in the RV electrical codes, specifically Article 551 of the National Electrical Code, "Recreational Vehicles and Recreational Vehicle Parks". Some libraries have it, but otherwise it is not a cheap book.
Walter the problem is not how well sealed the conduit is sealed, but rather that the Temp changes it will see in an A/C duct.
A/C is already known for causing a lot of condensation just by the nature of how it works. But running a conduit inside a A/C duct sealed or not is going to cause the conduit to generate condensation inside of it even if it is sealed because your going to be refrigerating it.
At least that is the way I see it.
;D BK ;D
For the record, GM & MCI ran wire chases through the ducts before buses had centralized heat and air. Obviously low voltage scenarios. You rarely ever hear of buses flambaying on their own accord due to wiring issues. Conversions however...
Quote from: B_K on March 24, 2017, 11:59:45 AM
Walter the problem is not how well sealed the conduit is sealed, but rather that the Temp changes it will see in an A/C duct.
A/C is already known for causing a lot of condensation just by the nature of how it works. But running a conduit inside a A/C duct sealed or not is going to cause the conduit to generate condensation inside of it even if it is sealed because your going to be refrigerating it.
At least that is the way I see it.
;D BK ;D
That would be true if the air inside the conduit had enough moisture, but what if the air was dry, or the conduit had desiccant in it to keep it dry, and then sealed?
Quote from: DoubleEagle on March 24, 2017, 07:41:01 PMThat would be true if the air inside the conduit had enough moisture, but what if the air was dry, or the conduit had desiccant in it to keep it dry, and then sealed?
I live near the coast of North Carolina. I'm sure it's 110% different for Clifford, and Geoff, and ThomasinNV, and the other folks in the "desert west", but where I live, if it's "sealed" that means that you've captured water in that conduit or air line or chassis cavity and it's going to come back to hurt you. Also, moisture seems to get into "sealed" areas but can't get out -- I'll let you guess how that works out.
What seems to work best for us is "flow through" air, deflectors to keep rain or road spray etc. out as best as possible, and drains at low points.
But sealing it to keep it dry -- ain't gonna happen.
Quote from: Oonrahnjay on March 25, 2017, 05:17:04 AM
I live near the coast of North Carolina. I'm sure it's 110% different for Clifford, and Geoff, and ThomasinNV, and the other folks in the "desert west", but where I live, if it's "sealed" that means that you've captured water in that conduit or air line or chassis cavity and it's going to come back to hurt you. Also, moisture seems to get into "sealed" areas but can't get out -- I'll let you guess how that works out.
What seems to work best for us is "flow through" air, deflectors to keep rain or road spray etc. out as best as possible, and drains at low points.
But sealing it to keep it dry -- ain't gonna happen.
Never say never. ;D The conduit system that kept my wires dry on my dump trailer were the vapor-proof type prescribed in explosive hazard conditions. There were mechanical seals at every fitting. For our purposes in a bus conversion, a product like Polywater FST foam duct sealant would work to seal the ends of conduit runs. It is a closed cell expanding foam that would hold even under pressure conditions. There are probably other brands as well. For the purpose of running conduit through a cooled passage, that should work. There are many conditions in the NEC (National Electrical Code for our international friends) that require the sealing against moisture and gas vapors in industrial and underground environments.
I've had the best luck by sealing it the best I can - then planning on how to deal with the water when it gets in.
Best to not go looking for trouble. . . .
Some have used chases in the back of the upper cabinets to provide access for wiring. While not perfect, it sure is handy!
K maybe I should have clarified it a little earlier. The electrical wiring would be running BESIDE the ABS heat/cool ducts inside it's own plastic conduit while both contained within a smallish cover panel at the floor/wall meeting.
I did not think about the condensation that may be present. This may be an issue but looking at the condition of the original HVAC runs I have my doubts.
I would think that should work, may want to wrap the air duct with some sort of insulation to prevent/reduce any condensation issues on the outside of the pipe. Then you are not losing cooling before it gets to the register. Depending on the area you are in, may not be a big deal, but here in the Midwest it can get quite humid.
I'm no expert but if I remember correctly condensation self generates as temperatures rise and fall.
So that is why I believe putting the conduit inside the A/C ducts is going to produce condensation.
But again I'm not a HVAC person, but I did stay in a Holiday Inn Express once.
;D BK ;D
I did one of two things. Thing #1 was to take the cable/wire down through the floor and traverse the distance in the bays, then come back up through the floor. It requires drilling a hole and using a grommet in the bulkheads that separate the bays, but they're aluminum and are easily drilled. Thing #2 was that above my windows, I built window valences that have a space behind them. In a lot of places, this acts as a wire chase where I can go the entire length of the bus. In some spots, I've installed LED lighting that's directed upward and reflects off of the ceiling, producing a nice, soft light. In one or two really tricky spots, I actually ran conduit so that the wire would have its own protected run. I probably overbuilt my electrical system with regard to wire sizing and chafe protection, etc, but I REALLY don't want to ever deal with a fire on board.