Plumbing Plan, Comments Appreciated - Page 2

Biscuitsjam · 04-04-2018, 09:54 AM

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.

dbhost · 04-10-2018, 12:45 PM

Quote:

Originally Posted by miscrms

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

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?

miscrms · 04-11-2018, 03:42 PM

Quote:

Originally Posted by dbhost

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, that’s 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 you’re less likely to have it “lock up” or have the main pump kick on and fight the recirculating pump. I’ve seen them used in home applications before, but not necessarily RVs, so we’ll see how it goes.

Rob

Jolly Roger bus 223 · 04-11-2018, 06:59 PM

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.

dan-fox · 04-12-2018, 01:33 PM

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.

Iceni John · 04-12-2018, 03:09 PM

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

dan-fox · 04-12-2018, 03:57 PM

Voila! You are the sensor and the logic. I hope you don't get a dent in your thumb.

CaptSquid · 04-12-2018, 05:51 PM

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.

miscrms · 04-13-2018, 02:42 PM

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 it’s 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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