Heat exchanger and header tank and expansion tank

[blackdove1256]

I read the posts regarding FWC, expansion tanks and header tanks. I'm confused.

I have a horizontal HEX with four fittings. Two for raw water. Two for anti freeze. I need some help (pics too) of how/ where to put the expansion tank and if I need a header tank that would be pressurized.

Anyone have any thoughts. Many thanks.

Gregg

[ndutton]

Here is my system with two electric coolant pumps in series, header tank and recovery reservoir, water heater

[blackdove1256]

HEX and Header tank pics

Thank you ever so much. The diagram really makes it crystal clear how to set this up.

Gregg

[blackdove1256]

Head tank for FWC engine

Now that I have a diagram to work with, I tried to find a head tank with two fittings (in/out) and the overflow port. Without having to sell my children, I haven't had much luck. Plenty in the UK and Australia at reasonable prices, but not the US market.

Two thoughts. Maybe I'm not calling it by the appropriate name. Or, my research is faulty. Second one is not the case.

Anyone have any ideas where I can get a small tank like this? Thank you and have a great weekend.

Gregg

[ndutton]

Anyone have any ideas where I can get a small tank like this?

They're available in aluminum from Summit Racing and Jeg's for around $100.00, ebay has them in plastic for around $30. If you're looking for a better deal, check the local automotive junk yard. All cars these days have them.

When doing your searches, look for expansion tank, NOT recovery tank. The term I've used, header tank, is what we called it at Islander Yachts.

[Tim]

Can you post a picture of your horizontal heat exchanger? You may not need a header tank.

[sastanley]

Gregg, Neil is right..the terms are weird..not everyone calls them what we would call them these days..Until the last two cars I owned, the rad cap was on the rad and we had an overflow tank...not so much anymore..(uh oh, I am getting old.)

But anyway, old school car racers face the same dilemma we do, so check on some of the car racing sights to find what you are looking for...I think expansion tank is a good term.

[Wrsteinesq]

The raw water anti-siphon

Neil, could you please elaborate on the working of the anti-siphon valve in your raw water circuit? I think its intended function is to prevent water from continuing to flow from the thru hull all the way thru the circuit into the exhaust mixer when the engine is off. In most cases (I think including yours) that exhaust mixer is a water lift muffler. I think the idea is to prevent the water lift muffler from filling with water and backing up into the engine.

Would there be any point to installing an anti siphon valve if the magenta raw water circuit terminated not at a water lift, but at a standpipe? I’m not sure how a siphon would be established in the first place, since I think the design of a standpipe would effectively serve to break any siphon. But even if a siphon were somehow established, wouldn’t water be flowing from overboard to overboard? Maybe I’m missing some important consideration. Thanks—-

[ndutton]

Your understanding of the role an antisiphon plays is spot on as is your understanding of different exhaust systems. A waterlift system involves below the waterline components and therefore it's possible for an unchecked siphon to overfill the waterlift and back up into the engine creating the usual havoc. The antisiphon introduces air to break the siphon. The common device is a one way valve, mine is an open vent in the loop. I prefer the open vent because there are no moving parts to fail or maintain.

A properly engineered and installed standpipe system has no water bearing components below the waterline so a siphon is not possible negating the need for a device to prevent it.

[Wrsteinesq]

Thank you, Neil. Good to have confirmation. In a similar vein, and perhaps at some risk of taking this thread a little farther afield, would the same thinking apply to a PSS installation, which is part of the same circuit under discussion?

I have a PSS bellows instead of a traditional stuffing box. There is an option to “power lubricate” the PSS by tapping off of the raw water exhaust discharge and using that to fill the PSS bellows. Thus exhaust discharge water flows not just to the standpipe but also to the PSS. Of course, the PSS is well below the waterline, so there is always the risk that the line could break or maybe come loose. I took that route so I could test my engine and prop shaft installation on the hard without destroying the cutless bearing. My sense is that since it’s tee’d off the exhaust water line, and that goes to the top of the standpipe (which coincidentally acts as a siphon breaker) that there is also no need of a siphon breaker here, although it still might be prudent to run the hose high, above the waterline, coming from the PSS. Again, am I missing anything here? Thanks!

[ndutton]

Correct again. All you have to get over is having a hose connected below the waterline without a valve in case of a problem. Some are good with that, some not. Then again, I don't see why a valve couldn't be incorporated either. A factor in that decision is not giving some insurance actuary an excuse to deny a claim.

I did a similar arrangement on my Westsail with a conventional stuffing box and bearing in the keel deadwood. The purpose was to give the bearing actual flow instead of just immersion. As the boat was being loaded on the truck to haul it out of the boatyard for launching I jumped up in the cockpit to give the engine one more test run. Half the "experts" in the yard were running around like Chicken Little screaming at me that I had a massive leak, shut the engine down!! I said no, it's supposed to do that. You should have seen the looks on their faces, "Huh? What??" They'd never seen nor even heard of such a crazy-a$$ thing (1987).

The engine had a waterlift with the normal antisiphon but I put an additional antisiphon in the hose for the bearing. Not necessary if it's connected to the top of the standpipe though.