Recirculating shower warm up time

[Dave01a]

This is a question / survey post. I'm considering adding a recirculating shower to my conversion van. I travel for work, and 80% of the time I have access to a land based shower. The other 20% usually happens after a break down or some other reason I couldn't make my planned destination. DOT kinda frown on breaking the 14 hour rule.


First off, shower alternatives are not in the discussion. I have VERY oily skin and hair, so daily hot showers are a requirement. My planned system would be 12V DC, but let me know if you are running 24V or 48V.



I have four questions for those of you that have / use a recirculating shower:


1. Water capacity USED, not the system capacity of you are only partially filling it.
2. GPM of your pump.
3. Wattage / Voltage of your heating element.
4. The all important question, rough heat up time. From fairly quickly, to go out and pick up a sandwich while it's pumping and heating up.


Thanks in advance for the info!

[booster]

Originally Posted by Dave01a

This is a question / survey post. I'm considering adding a recirculating shower to my conversion van. I travel for work, and 80% of the time I have access to a land based shower. The other 20% usually happens after a break down or some other reason I couldn't make my planned destination. DOT kinda frown on breaking the 14 hour rule.


First off, shower alternatives are not in the discussion. I have VERY oily skin and hair, so daily hot showers are a requirement. My planned system would be 12V DC, but let me know if you are running 24V or 48V.



I have four questions for those of you that have / use a recirculating shower:


1. Water capacity USED, not the system capacity of you are only partially filling it.
2. GPM of your pump.
3. Wattage / Voltage of your heating element.
4. The all important question, rough heat up time. From fairly quickly, to go out and pick up a sandwich while it's pumping and heating up.


Thanks in advance for the info!

If the shower is almost always needed per your description, you might want to consider adding a tank that you could heat with engine heat while driving as it sounds like that would be possible. Electric backup just in case.

[Dave01a]

Unfortunately the van is usually the TOAD in these situations. Although a heat exchanger is on the list of possibilities, just not the preferred. Trying to keep it self contained and portable for removal in cold temps.

[GeorgeRa]

You will need a large battery bank and charging system to electrically heat water, see attached site to calculate your energy demand.

https://gettopics.com/en/calc/water-heating-calculators

[Dave01a]

Yeah, that's part of why I'm asking for real world users. Calculated puts me at 45 to 55 minutes depending on incoming water temp according to that calculator. But the video's I've seen never mentioned a prolonged warm up time. Granted, I could easily pop a few quarts of water in the microwave on the inverter for a higher starting point with such a low water volume. Like I said, trying to get some real world users to comment.

[jrobe]

You probably need a propane tank and propane water heater. A propane water heater will heat up water to shower temps within a few minutes and is fairly cheap. There is no need for recirculation and the water pump takes minimal battery power. I can take an RV shower with 1 gal of warm water if I get wet, shut it off to soap up and then rinse off.

[Dave01a]

The question is for a recirculating shower.

[GeorgeRa]

You have the specific question about prolonged warming of water whatever it means, I suggest building a system and test it to check if physics apply to your system or not.

[booster]

Originally Posted by GeorgeRa

You have the specific question about prolonged warming of water whatever it means, I suggest building a system and test it to check if physics apply to your system or not.

I would have to agree we could use a lot more details of what is in place and what the goals are.


In general, when I hear of a "recirculating warm up" application it could be either with a tank water heater or an instant one. It simply uses a pump to circulate the same water in a loop, through the cold side as a return, to warm the piping and/or give an instant heater a chance to get started and warmed up. Very common in apartment buildings or homes where the faucets are a long ways from the water heater.

[Dave01a]

Conversion van setups are usually in the 1.5 to 3 total gallon range. The heat element is in a larger section of copper pipe, no tank, just a bit of a reservoir in the shower pan.

[booster]

Originally Posted by Dave01a

Conversion van setups are usually in the 1.5 to 3 total gallon range. The heat element is in a larger section of copper pipe, no tank, just a bit of a reservoir in the shower pan.

Are you talking about recirculating fresh water or used shower water from the shower pan?

[Dave01a]

Self contained SHOWER water.

Several filters, including a UV filter. Short term usage. As my initial post said, I have access to a land based shower roughly 80% of the time. The remaining 20 is usually due to a breakdown or something that prevents me from reaching my planned destination. Toss a couple of gallons in the recirculating shower, and I'm set. dump it in a few days of not needed.

[GeorgeRa]

Using electrical heat source element only to heat water, especially DC powered is rather rare in commercial or DIY conversions. Folks often use gasoline, diesel, LPG or marine water heaters, some have an auxiliary electrical heating element to be used if there is excess of electrical energy. I use diesel furnace with marine water heater which has built in 750W 120VAC element. I only use the 750W heater on shore power.

[Dave01a]

The DC supply is in place, any other source will require adding equipment to an already tight configuration.

FYI, this is a WORK vehicle, not a vacation and travel vehicle.

[GeorgeRa]

How big is your battery bank?

[peteco]

Check this article out. I assume you would be heating the water while the van is being towed, with 12v power supplied from the tow vehicle. Pay attention to the water heater current requirement. You may need to increase the size of the 12v power wire from the tow vehicle to the van.

https://www.thervgeeks.com/12-volt-water-heater/

[Dave01a]

Currently have 600W of solar, and 400Ah of LiFePO4 battery. Room to add another 200W of solar, and plenty of room for more batteries of needed.

No power from tow vehicle, they are all rentals being delivered.

Usually I have a bit of a heads up not being able to make my daily destination, but not always. Firing it up ahead of time with the solar and battery isn't a problem, but my time between fuel stops is 2 - 3 hours, vs. a 45 - 55 minute warm up time. Hence my asking for real world usage info.

Surprisingly, I've put this question on several forums, and have yet to get a response from an actual user.

[Dave01a]

Peteco,

I had to smile, I was working at an RV dealership when Winnebago introduced those units. Worst bit of engineering ever! You were lucky to get a year out of the transmission, and no option for a generator.

The only 'neat' thing about them was the pull out shower walls. The closet was for the toilet. The shower pan was in the center walkway with a board over it. Lift the board and pull out the walls for a shower. But it had to pump up to the gray water tank. You kept the hair out, or you replaced the lift pump fairly regularly.

Couple of years in they did a major upgrade on the engine and transmission, and carved out a spot in the back for a tiny generator.

All chuckling aside, that is one of many older articles using an open system large tank water heater ( 6+ gallons ), vs a closed recirculating system ( 1.5 -> 3 gallons ).

[Sensfan]

Originally Posted by Dave01a

The DC supply is in place, any other source will require adding equipment to an already tight configuration.

FYI, this is a WORK vehicle, not a vacation and travel vehicle.

You may want to consider communicating with with these guys in Ontario (north of Toronto). We have had not used their services; however, they are a family run operation that appears to have experience with innovative system design ideas. They may be able to offer interesting, non previously discussed “off grid" ideas adaptable to your “work vehicle” situation.
https://www.rayoutfitted.com/solar

[booster]

Unusual setup for us RV, fresh water, grey water tank people to recognize so a full description of the system up front would have saved a lot of time and posts, it think.


You can do the calculation for this pretty readily, I think.


3 gallons of water or 25.2#


50*F temp rise


1 btu/hr will raise 1# of water 1*F


25.5 X 50 = 1260btu/hr


1 btu/hr = .293watts



1260 X .293 = 369 watts



Assume about 5 amps or 60 watts per 100 watt panel in normal/decent sun conditions.


369/60 = 6.15 100 watt panels needed to get that much heat in one hour in a perfect world and no heat loss.


You can fill in your own parameters if different.


I did this very quickly so an accuracy check of it all by someone would be a good idea