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Old 04-04-2018, 09:54 AM   #21
Skoolie
 
Join Date: Dec 2017
Location: North Pole, AK
Posts: 107
Year: 1998
Coachwork: Amtrak RE
Chassis: International 3000
Engine: T444e
Preventing recorculating hot water from the cold line is a simple fix.

1. Change where the recirculating hot water is spliced in to merge with the hot water intake just before it enters the tank.
2. Add a check valve to prevent your recirculating hot water from going "backwards" into the cold side of your thermostatic mixing valve and the cold water line.

I think a couple easy changes could minimize your need to ooen/close valves during operation also.
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Old 04-10-2018, 12:45 PM   #22
Skoolie
 
Join Date: Oct 2015
Location: League City, Texas
Posts: 219
Quote:
Originally Posted by miscrms View Post
I've finished my first cut at a plumbing plan, would appreciate comments / feedback. Bus is a 40' Blue Bird All American RE being converted for full time living, family of 5.

Thanks,
Rob



Some of the components I'm looking at using:

Bladder / tanks:
http://www.skoolie.net/forums/f50/bl...nks-19652.html

Marine Water Heater (Electric / Heat Exchanger):
https://www.amazon.com/Kuuma-Water-H...ater+exchanger

Shurflo Marine Pump / Acumulator Tank:
http://shurflo.com/images/files/Mari...-4902-4212.pdf

City / Fill Inlet
https://www.amazon.com/dp/B00HTWP59S...v_ov_lig_dp_it

Drain / Grey Outlet
https://www.amazon.com/dp/B00HRX14E4...v_ov_lig_dp_it

Check Valve / Back Flow
https://www.amazon.com/dp/B000EDUTN6...v_ov_lig_dp_it

Pressure Regulator
https://www.amazon.com/dp/B003BZD08U...v_ov_lig_dp_it
https://www.amazon.com/dp/B01N7JZTYX...v_ov_lig_dp_it

Thermostatic Mixing Valve
https://www.amazon.com/dp/B01MS3X57O...v_ov_lig_dp_it

Recirculation Pump
https://www.amazon.com/dp/B0196WL6GY...v_ov_lig_dp_it

Strainer
https://www.amazon.com/Female-Strain...water+strainer
https://www.amazon.com/dp/B000F898B4...&pd_rd_w=ZZp5l
https://www.amazon.com/dp/B075PPLT3V..._t2_B0171GKS1Q
Please forgive my ignorance here on such matters, but I am trying to learn as quickly as I can...

Can you please explain the warm return / recirculation? It looks like you are pumping back against the flow of the other pump lower in your diagram...

I'm not sure how or why you would use warm / hot recirculation. Is this to "pre warm / heat" the water in the pipes before sending it to the faucets thus reducing water waste getting the water to your desired temp?
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Old 04-11-2018, 03:42 PM   #23
Skoolie
 
Join Date: Aug 2017
Location: Phoenix, AZ
Posts: 228
Year: 1997
Coachwork: Blue Bird
Chassis: AARE 3903
Engine: Cummins 8.3L 12v
Rated Cap: 78
Quote:
Originally Posted by dbhost View Post
Please forgive my ignorance here on such matters, but I am trying to learn as quickly as I can...



Can you please explain the warm return / recirculation? It looks like you are pumping back against the flow of the other pump lower in your diagram...



I'm not sure how or why you would use warm / hot recirculation. Is this to "pre warm / heat" the water in the pipes before sending it to the faucets thus reducing water waste getting the water to your desired temp?


Yes, thats the idea. The water in the hot supply pipes gets cold from sitting, so you can run the recirculating pump to flush the cooled water out and replace it with hot before opening the hot tap to reduce waste. Ideally when you do that the system is just sitting at stable pressure, so the main pump is idle. The accumulator should help keep the pressure stable while the recirculating pump is running so hopefully youre less likely to have it lock up or have the main pump kick on and fight the recirculating pump. Ive seen them used in home applications before, but not necessarily RVs, so well see how it goes.

Rob
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Old 04-11-2018, 06:59 PM   #24
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A correct hot water return system is piped into the cold water inlet with a check valve on both lines before the connection point of the DHWR(domestic hot water return) it can be also be piped in to the cold side of the TMV (thermostatic mixing valve). The idea is to war up the cold water going into the hot water equipment to help it heat the water by using water that is already tempered (warm) instead of the heater having to turn cold into hot it can spend less effort and last longer turning warm into hot
The idea of the return pump is to keep hot water on the ready at the farthest fixture fro the water heater in big buildings.
The hot water is there instead of running the water for minutes to get the hot water there.
For water saving it is nice but for boondocking it cost power to run that pump especially if it's not on a timer to only run just before usage hours and shut down after usage hours.
An instantaneous will always run to keep a pump happy and will be dead in a few years unless controlled properly or piped to a storage tank like an old 120v water heater tank and the instantaneous run the tank loop temp and the hot water and hot water return loop draws off of the tank
That is just my opinion of a domestic return system on the large size systems I work with and trying to use the idea in a schoolie?
If your Hooked to power then you can afford to run a pump and a water heater but if you are working off grid it would strain an electrical hot water system.
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Old 04-12-2018, 01:33 PM   #25
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I think the trick would be to have a hot water loop in your vehicle just like in a building but have it set off by a button at the point of use and just run until a temp sensor at the farthest point is satisfied, or simply on a timer. You'd still have a wait between when you pushed the "I want hot water" button and when it was available, but you wouldn't waste water or energy.
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Old 04-12-2018, 03:09 PM   #26
Bus Nut
 
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Location: Orange County, CA
Posts: 653
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Chassis: Crown Supercoach II (rear engine)
Engine: Detroit 6V92TAC, DDEC 2, Jake brake, Allison HT740
Rated Cap: 37,400 lbs GVWR
When I connect hot water to my bathroom handbasin's faucet I plan on using a simple small brass push valve to temporarily divert not-yet-hot-enough water back into one of the freshwater tanks. Hold the valve's button down until it begins to feel warm, then release it and hot water will flow as normal from the faucet. Simple, easy, effective. I already have the 1/2" return line connected into the driver-side fresh tank. Amflo makes a suitable small brass valve, and even if not a full 100% of the almost-hot water makes its way back to the freshwater tank it will still reuse most of it to prevent it going straight into the gray tank. Mind you, with 220 gallons of freshwater capacity maybe this isn't the highest priority!

John
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Old 04-12-2018, 03:57 PM   #27
Bus Crazy
 
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Location: SW New Hampshire
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Voila! You are the sensor and the logic. I hope you don't get a dent in your thumb.
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Old 04-12-2018, 05:51 PM   #28
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I'd use a demand-type water heater or one that one turns on prior to use rather than a holding tank heater.

I purchased a 30 litre boiler from Amazon.de. This will do well to provide enough hot water with which to work, including showers. One only needs to turn this unit on prior to use. These heat up quickly.
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Old 04-13-2018, 02:42 PM   #29
Skoolie
 
Join Date: Aug 2017
Location: Phoenix, AZ
Posts: 228
Year: 1997
Coachwork: Blue Bird
Chassis: AARE 3903
Engine: Cummins 8.3L 12v
Rated Cap: 78
I had originally planned to go tankless, ended up with a tank for 2 reasons.

1) Ability to heat from engine coolant (engine heat or Webasto) via heat exchanger and store hot water for later use.

2) Ability to use excess solar when its available to heat water and store for later use.

My intent is to use a manual warm before use switch on the recirculating pump. Check valve on the re-circulation loop outlet seems like a good idea.

We have a large battery / solar setup, so really not worried about the extra power use for the relatively recirculating pump. Water usage is expected to be the limiting factor for our boondocking.
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