Plumbing & electrics

[Zephod_beeblebrox2]

I've been thinking hard about plumbing and electrics since I'm avoiding the use of propane and gasoline.

This is what I came up with...

Plumbing..
No handbasin, no kitchen sink.
A shower base that empties into a grey tank. All kitchen water and hand washing water gets tipped into it. Also a handy urinal - lol
Water - cold only - comes from under body holding tanks.
There is no electric pump. Instead there is a faucet under the bus (hidden). Also an old fashioned hand pump inside the bus, pointed into the shower base.
Hot water is achieved by heating cold water in a kettle or by dropping a heating element into a bucket.

Electricity.
At the back of the bus is a breaker box. On the side there's a 50A socket with a cover.
Riveted to the body ribs, close to the chassis is a metal conduit that takes 4 electric cables - each on an individual 15A breaker. There are two main breakers that get switched out. A 30A breaker for 30A connections and a 50A breaker for 50A connections.
The four cable s lead to individual 15A sockets.
There might be a 5th cable leading to a 12v battery charger.

Batteries.
There will be two (maybe just one) marine deep cycle batteries.
These will be charged by the alternator via a smart relay.
Also the battery will be charged via mains power.

The battery provides power for extraction fans (computer cooling fans,), USB chargers and power for 120w 12v water heating coils.
Possibly also for laptop charger.

Solar\wind don't figure immediately in my plans. Wind speed in my area is just too low at 3mph. Solar is stupidly expensive at $1.89 a watt.

[milkmania]

the things I've learned about electrical & plumbing....
1) Electricity will shock the $hit out of you
2) $hit rolls downhill

I've lived almost 50 years with these principles.

[Zephod_beeblebrox2]

I like the look of the 12v showers though I might engineer my own. They pump hot water from a bucket through a shower head. Maybe I'll rig up some kind of pull so that I can switch the water on and off while showering.

[nat_ster]

I'm not sure what the intention is behind starting this thread?

I feel this should have been posted in your build thread, so we don't clutter up this site with meaningless threads.

Nat

[Zephod_beeblebrox2]

This is a thinking thread, not something I have achieved. The bus build thread is about things that have been achieved.

[jazty]

Originally Posted by Zephod_beeblebrox2

power for 120w 12v water heating coils.

Will a 120w heater coil ever heat up more than a cup full of water? Do you have a link? I'm curious...

Originally Posted by Zephod_beeblebrox2

Solar is stupidly expensive at $1.89 a watt.

That's only true for the flexible panels or the expensive 12v stuff they sell at RV places (and you know it ). Solar can be found for near $1.00 per watt.

[Zephod_beeblebrox2]

Originally Posted by jazty

Will a 120w heater coil ever heat up more than a cup full of water? Do you have a link? I'm curious...


I used a cup heater to heat water for my laundry when I was living/backpacking for months at a time in eastern Europe. It took a while! But connected straight to a solar panel during the day...


That's only true for the flexible panels or the expensive 12v stuff they sell at RV places (and you know it ). Solar can be found for near $1.00 per watt.

Flexible is the only way to go IMHO.

[opus]

Originally Posted by milkmania

the things I've learned about electrical & plumbing....
1) Electricity will shock the $hit out of you
2) $hit rolls downhill

I've lived almost 50 years with these principles.

In that order?

[family wagon]

Originally Posted by opus

In that order?

Well, you sure don't want to be at the bottom of a hill when you discover the thing about electricity! Better to learn #1 first!

It's easy enough to figure wattage and temperature rise. Specific heat of water is around 1 Btu per pound per degree F (it varies with temperature), so if we have a mug holding 8 fluid ounces of water at 50 F and we want to raise it to 120 F, that's 0.52 pounds times 70 degree rise so 36 Btu needed (ignoring heat lost to the mug, ambient, etc). That's 0.0106 kw-hr, 10.6 watt-hours, so at 120 watts input it'll take 5.3 minutes (longer in the real world, where the heater doesn't achieve its rated output and heat is lost to the mug etc).

[Zephod_beeblebrox2]

Neat calculation. That's about what it took with my Soviet cup heater.

Now, imagine all the power from a 100w solar panel going into 5 gallons of water over 8 hours.

The water will be tepid but warmer than the ambient temperature.

[nat_ster]

I agree.

Small watt electrical heating elements are great for heating water over a long period of time.

Like from solar or a wind turbine.

Nat

[Zephod_beeblebrox2]

Originally Posted by nat_ster

Small watt electrical heating elements are great for heating water over a long period of time.

Like from solar or a wind turbine.

Nat

That's what I was thinking... Fill the bucket in the morning, heat the water all day and shower in the evening!

[family wagon]

Originally Posted by Zephod_beeblebrox2

Now, imagine all the power from a 100w solar panel going into 5 gallons of water over 8 hours.

The water will be tepid but warmer than the ambient temperature.

5 gallons = 41.5 pounds, 8 hours times 120 watts = 960 watt-hours = 3275 Btu. It can raise the water about 79 degrees F, so if it started at 50 F it could be at 130 F by end of day. But 8 hours is probably on the optimistic side for daily solar production at full power, even in the summer. (and remember we're still ignoring heat lost through the uninsulated walls of the bucket etc)

If instead that water were pumped through a collector designed for solar heating water, or even just left sitting stagnant in a collector big enough to hold the full 5 gallons, it would heat the water much faster. Estimating 1600 kWh/m2 annually from a solar irradiance map for North America off wikipedia, that's 407 watts available on average per square foot. If it's 60% efficient, then it takes just 4 hours to heat the same 5 gallon bucket. A square foot of solar water heater is generally much cheaper than a square foot of solar panel.. this is why you don't often see water heated by PV systems. It can be done, and maybe it's more convenient to store energy in a battery and heat water later instead of storing energy as heated water. But usually hot water is needed at a scale that makes PV-powered heating unattractive.

[nat_ster]

I agree, using a solar water heater would be more efficient.

I will have both.

Also, there are times in the spring and fall when it gets hot in the day time, but freezes at night. This makes the solar water heater harder to use.

However, where I live, when the sun is not out, the wind is often blowing. So I will still use the electricity to heat the water.

Nat

[Zephod_beeblebrox2]

Originally Posted by family wagon

5 gallons = 41.5 pounds, 8 hours times 120 watts = 960 watt-hours = 3275 Btu. It can raise the water about 79 degrees F, so if it started at 50 F it could be at 130 F by end of day. But 8 hours is probably on the optimistic side for daily solar production at full power, even in the summer. (and remember we're still ignoring heat lost through the uninsulated walls of the bucket etc)

If instead that water were pumped through a collector designed for solar heating water, or even just left sitting stagnant in a collector big enough to hold the full 5 gallons, it would heat the water much faster. Estimating 1600 kWh/m2 annually from a solar irradiance map for North America off wikipedia, that's 407 watts available on average per square foot. If it's 60% efficient, then it takes just 4 hours to heat the same 5 gallon bucket. A square foot of solar water heater is generally much cheaper than a square foot of solar panel.. this is why you don't often see water heated by PV systems. It can be done, and maybe it's more convenient to store energy in a battery and heat water later instead of storing energy as heated water. But usually hot water is needed at a scale that makes PV-powered heating unattractive.

Yup. I appreciate that but while the plan is eventually to have a hit tank under the bus, the budget says a bucket inside.

Now, if I'd been less concerned with building in absolute privacy then my construction techniques would have been different and I might have put in a pot belly stove.

There are advantages and disadvantages all ways.

[jazty]

Originally Posted by Zephod_beeblebrox2

Flexible is the only way to go IMHO.

For completeness I'll add that flexible panels when installed flush to the roof of the bus, though neat and tidy, are the least efficient and most expensive means of powering a bus by solar.

Originally Posted by family wagon

5 gallons = 41.5 pounds, 8 hours times 120 watts = 960 watt-hours = 3275 Btu. It can raise the water about 79 degrees F, so if it started at 50 F it could be at 130 F by end of day. But 8 hours is probably on the optimistic side for daily solar production at full power, even in the summer. (and remember we're still ignoring heat lost through the uninsulated walls of the bucket etc)

If instead that water were pumped through a collector designed for solar heating water, or even just left sitting stagnant in a collector big enough to hold the full 5 gallons, it would heat the water much faster. Estimating 1600 kWh/m2 annually from a solar irradiance map for North America off wikipedia, that's 407 watts available on average per square foot. If it's 60% efficient, then it takes just 4 hours to heat the same 5 gallon bucket. A square foot of solar water heater is generally much cheaper than a square foot of solar panel.. this is why you don't often see water heated by PV systems. It can be done, and maybe it's more convenient to store energy in a battery and heat water later instead of storing energy as heated water. But usually hot water is needed at a scale that makes PV-powered heating unattractive.

Great calculations! If somebody could chime in with the calculations for heat loss from an uninsulated bucket I'd be much obliged. I would guess that there would be a limit that would be reached well before 130F due to that ambient air temperature.

[Zephod_beeblebrox2]

At the moment my internal temperatures are about 97F. The high point was 139F.

[Zephod_beeblebrox2]

This looks interesting - a list of what all the gadgets use. It looks like a raw food diet perhaps supplemented by cooking outside is in order!

Interestingly, I looked at a peltier unit online. Somebody had coupled a peltier cooler unit $9 with a computer fan and a heat sink. They claimed frost would appear almost instantly on the peltier device. The rated power consumption was high at 12v, 5A or 60w.

On the other hand, with one of those units, a simple cooler can be turned into a refrigerator with advantages such as custom size.

If a peltier unit was planned into the power budget, that could be the way to go.

For the moment, I found my breaker box will fit under my kitchen countertop to a rib on the side wall. Now all I have to do is to work out the cabling. I was going to put it at the back and have cabling and conduit. That would have been more expensive though.

[family wagon]

Originally Posted by jazty

Great calculations! If somebody could chime in with the calculations for heat loss from an uninsulated bucket I'd be much obliged. I would guess that there would be a limit that would be reached well before 130F due to that ambient air temperature.

This is the sort of question I'd answer experimentally rather than try to calculate or even estimate. Unfortunately, I'm fresh out of 120 watt heaters! Anybody else want to try? If it were me, I'd just set a filled bucket outside in the morning, plug in the heater, and leave it for the day. At some point it'll reach equilibrium where the heat input from electricity equals the heat lost to the ambient and the temperature doesn't rise any higher. I did essentially this same test with a pair of electric 2250 watt baseboard heaters a few winters ago to estimate the heat loss of my bus before I began tearing it apart.

[crazycal]

Originally Posted by family wagon

It's easy enough to figure wattage and temperature rise. Specific heat of water is around 1 Btu per pound per degree F (it varies with temperature), so if we have a mug holding 8 fluid ounces of water at 50 F and we want to raise it to 120 F, that's 0.52 pounds times 70 degree rise so 36 Btu needed (ignoring heat lost to the mug, ambient, etc). That's 0.0106 kw-hr, 10.6 watt-hours, so at 120 watts input it'll take 5.3 minutes (longer in the real world, where the heater doesn't achieve its rated output and heat is lost to the mug etc).

Man, this was on the tip of my tongue. I was going to write the same thing but went to go make a cup-o-joe and you beat me to it. Now you look like the smart guy...and me...not so much.