Dredge Hot Water Heater

[Leonard]

I don't think I'll put my bed over the hot water heater.
The pop-off on mine is set at 150 psi. There is 150 psi in the street in front of my house. I've seen 150 psi in the house when the outside regulator failed. The clue was the pop-off dripped. I keep a pressure gauge on my water heater which I check periodically.
Leonard

[Geowizard]

Leonard,

That's a real good idea!

I'm going to do that too.

- Geowizard

[easy goer]

I am looking at including a pressure relief valve as well. I have a friend here who is in the industrial pump field and is running my project by some of his fluid engineer friends in the hopes of keeping me from cooking or blowing myself up. He is a pretty good friend, as long as my wife isn't helping I feel they are working in my best interest. Unfortunately, at this stage of my life I am worth way more dead than alive!!!

Easygoer

[Geowizard]

Fluid engineering;

This is the plumbing equivalent of a battery and light bulb...



Pump1 is controlled by a PID Temperature controller.

Pump2 is controlled by the diver.

The heat exchanger is mounted onto/over something that gets warm/hot, not greater than 200 degrees.

There is no possibility of explosion. It is temperature controlled by the PID controller.

It's low cost too!

- Geowizard

[Micropedes1]

Easy,
All of this is good information, but let's see if an old-time dredger can set you straight.

Start with a simple "Y" connector at your pump. You need one with a shut-off on each side. A short water hose should be connected to one side of the "Y", making certain to use a hose washer/strainer just like the one on the back of your washing machine. The other half of the "Y" can be used to supply a blaster nozzle.

For the heater portion, you can get by with 25 feet of 3/8 copper (enough for 1-2 divers). For more divers, you will be better served with 1/2 inch tubing (same length). Putting the tubing on the outside is simply not acceptable. It will serve, after a fashion, but the heat recovery is sorely lacking.

Stopper one end of the tubing and fill from the other end with dry sand. Wrap the stoppered tubing around the smallest mandrel that you can find (I usually start with 1.5 inch wooden dowel). The sand keeps from crimping the tubing excessively while wrapping. After coiling the tubing, hammer it against a solid surface and rotate while pouring to remove all the sand. You should be able to blow freely thru it when finished.

Remove the end of the exhaust that lacks the exhaust port. Drill 2 holes to accommodate input and exit of copper water lines. Install heater coil and reweld the end plate. (this is usually easier to do with a fresh piece of flat stock rather than piece the original back into place).

Use swage or flare fittings to attach hose bib connectors to both ends of the heater coil. Check for leaks.

[Micropedes1]

You are almost guaranteed to exercise profane vocabulary while trying to fit your constructed coil back into the existing muffler assembly.

When you get ready to try it again, use a grinder to cut the exhaust barrel free from the exhaust flanges, leaving a couple of inches connected. Extend these exhaust tubes a few inches to get the "new" exhaust tube away from the motor for a bit more clearance and to give more distance between heater and pump.

Replace the barrel of the heater with over-sized 4 or 5 inch muffler tubing (from your local muffler shop). You will appreciate all the extra room when you try to insert a full-sized coil of 1/2 inch tubing. Seal both ends with flat stock and drill a 3/4 inch hole to vent the exhaust. Make darned sure that you do not puncture the heater tubing when drilling the exhaust vent (been there, done that).

Plumb as necessary.

[Micropedes1]

The most necessary part of your heater system is the surge tank. The bigger, the better.

The discharge line from your heater coil must be heat resistant hose (think washing machine hose again). Connect to the highest point on your surge tank via another "Y" connector. Remember that cold water line suggested for blaster use above? It really needs to be connected to the "Y" connector with your hot water line at the top of the surge tank. Adjusting the "Y" valves provides a positive pressure thru the heater coil at all times. Running it "dry" while the engine is running will burn thru the copper line quickly.

Pull your hot water from the bottom-most part of your surge tank via a connected water hose. This hose should have a 3/16 or 3/8 plastic hose fed thru its center and slightly exposed on the end. Silicone the ends of the hose to seal out cold water and to trap air within the heater hose.

You have enough hardware down in your dredge hole to contend with. You want that heater hose to float up out of the way. You will have the discharge end stuffed down the back of your wetsuit near your neck anyway. But if you prefer to have it tethered, then pass a loop of it under your weight belt, taking care not to obstruct the flow. (that's how you could get burned) BTW, all you really need for this is a good grade wet suit. it it gets too warm, simply remove the end of the hose from you wetsuit and let it hang.

[Micropedes1]

Make certain that the discharge line from your heater coil enters the surge tank from the top. That tank need to be secured to keep it from falling over and changing the positions of the input and discharge. In the unlikely event of a momentary stopped water flow, your discharge will turn to steam. That reservoir of water in the surge tank will give you some warning as it gets hotter and hotter. That means that you have adequate time to remove the discharge from the back of your wetsuit. The restricted flow is usually where you have it tucked into your weight belt.

[Micropedes1]

Oh, be sure to clean that filter screen daily, usually when you refuel. Better to be safe. Keep an extra on hand as rough handling sometimes punctures the screen and defeats its purpose.

Ran this set-up for 30+ years and have not gotten burned yet.

[Micropedes1]

The Geo/Precision pump on my bigger dredges simply had the thermostat removed and an aluminum plate in its place. A hole was drilled in the aluminum plate to regulate the water flow. Hose bib and unrestricted hose completes the set up. Matter of fact, the volume is sufficient to power a heated blasting nozzle. Cool, huh?

The ones running VW power have 100 feet of 1/2 inch stainless line inside a 12 inch exhaust chamber. No burn-thru issues when running dry.

Both of these were popular as everyone could enjoy a hot shower at the end of the day. A real treat when working in the remote wilds.