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View Full Version : Explain the "Y" adapter.....?


bigmac
11-29-2005, 07:34 PM
Sorry to be dense. I don't understand the engineering behind the "Y" adapter as a means of increasing heat through a HeaterCraft heater, nor am I clear on the mechanics of the install.

Currently, on my MCX, there are two heater hoses. One attaches to the circulating pump on the front of the engine, the other is connected to the intake manifold. I do understand that the "Y" adapter splices into the raw water line. What I don't understand...

does it splice in at the output hose from the raw water pump, between it and the transmission cooler?
how does it "splice in"? Adapter over the raw water pump output barb and then a double barb between the "Y" adapter and the tranny cooler hose?
which of the two heater hoses gets hooked up to the smaller branch of the "Y" adapter? The one from the circulating pump, I'm guessing?
this increases hot water flow through the heater core by using the higher-volume raw water pump instead of the less vigorous circulating pump?
does it matter which way the "Y" points?


Whew! Thanks...I feel unburdened having finally worked up the courage to ask the question.

rodltg2
11-29-2005, 08:04 PM
i dont understand the reason why the Y adapter increases heat at idle but thats what i have been told to do. i do know however that the return line to goes to it. ive heard it makes no differnce how you hook it up on the heater core because it will run both directions.

AirJunky
11-29-2005, 08:11 PM
Jeff in the R&D dept at Heatercraft told me it had something to do with the pump your using as a result of the Y install. The raw water pump pumps more volume at a higher rate than the engine water pump.
He might be a better source for that kind of info than you'll get here.

bigmac
11-29-2005, 08:25 PM
Jeff in the R&D dept at Heatercraft told me it had something to do with the pump your using as a result of the Y install. The raw water pump pumps more volume at a higher rate than the engine water pump.
He might be a better source for that kind of info than you'll get here.

So, the heater hose that is connected to the circulating pump should be disconnected, the pump fitting plugged, and that hose reconnected to the smaller branch on the "Y" pipe? Leave the heater hose that's connected to the intake manifold alone?

AirJunky
11-29-2005, 08:29 PM
Yep. You got it, BigMac.

bigmac
11-29-2005, 08:46 PM
Yep. You got it, BigMac.


Thanks for the help guys.

Leroy
11-29-2005, 10:06 PM
After reading extensively, I still find mystery around heaters! Especially when you have shower and heater! You are the first one to mention a circulating pump for the heater core? Normally there is hot water from engine to the heater core, back to the barb of the y if I understand this correctly, true? The circulating pump was in series with hot water in or cooler hot water out?

NOTE: ICBW


does it splice in at the output hose from the raw water pump, between it and the transmission cooler? YES

how does it "splice in"? Adapter over the raw water pump output barb and then a double barb between the "Y" adapter and the tranny cooler hose? ?
which of the two heater hoses gets hooked up to the smaller branch of the "Y" adapter? The one from the circulating pump, I'm guessing? You will want the water to flow back to the barb
this increases hot water flow through the heater core by using the higher-volume raw water pump instead of the less vigorous circulating pump? I believe it creates a venturi effect pulling water from the heater core
does it matter which way the "Y" points? YES

Whew! Thanks...I feel unburdened having finally worked up the courage to ask the question.

bigmac
11-30-2005, 12:44 AM
After reading extensively, I still find mystery around heaters! Especially when you have shower and heater! You are the first one to mention a circulating pump for the heater core? Normally there is hot water from engine to the heater core, back to the barb of the y if I understand this correctly, true? The circulating pump was in series with hot water in or cooler hot water out?

NOTE: ICBW


By circulating pump, I was referring to the engine's water circulation pump, as opposed to the raw water pump. I guess water from the block, once hot and the thermostat opens, is also circulated through the heater inlet hose (which is plumbed to the intake manifold and open to the cooling jackets), through the core and returned to the intake side of the engine's water pump. The Y pipe is supposed to go between the boat's raw water intake hose and the intake of the raw water circulating pump. The heater's return hose that used to go back to the water pump is now supposed to be connected to the 5/8 Y on the Y pipe, so water from the heater is now returned to the raw water intake hose instead of the engine's water pump. The Y pipe has a 1/8 inch hole that is supposed to slow down water flow and keep hot water in the heater core longer and therefore hotter. I guess.

My boat has a valve on the manifold fitting, which I presume is supposed to allow me to control the amount of flow into the heater core.

http://mccollister.info/valve.jpg

It seems to me that I could just close that valve down some amount and retard water circulation through the heater core, thereby accomplishing the same thing as the Y pipe with its 1/8 restricting hole.

Unless I'm wrong...

jimmer2880
11-30-2005, 08:15 AM
.....It seems to me that I could just close that valve down some amount and retard water circulation through the heater core, thereby accomplishing the same thing as the Y pipe with its 1/8 restricting hole.

Unless I'm wrong...

My "Y" adapter doesn't have a 1/8 restricting hole.

I put a shut-off valve on mine as well. I use it in the dead of summer when I don't want any heat going through the box (which will heat up the cockpit area even if the blower isn't on).

beef
11-30-2005, 09:56 AM
I got better circulation from placing the Y adapter before the raw water pump (between the thru-hull fitting and the rwp). This will allow the pump to pull through the Y at idle.

I also put in a couple of the brass garden hose splitters from Lowes. Use with 5/8" barbs and clamps to install on both the supply and return line. This will let you shut flow off in the summertime. By flipping the valves on the splitters, you can easily blow out the heater for < 32 nights in the fall, or use to pour antifreeze through the heater core for winterization.

bigmac
11-30-2005, 10:08 AM
My "Y" adapter doesn't have a 1/8 restricting hole.

I put a shut-off valve on mine as well. I use it in the dead of summer when I don't want any heat going through the box (which will heat up the cockpit area even if the blower isn't on).

I was reading about this stuff over on the Malibu forums. They are just as confused as we are. It all sounds like a bunch of voodoo to me. Lots of people on other boards quote Dan at Heatercraft, but nobody quotes him the same way twice. I got the impression that nobody really knows why the Y pipe works to increase heat at idle.

Supposedly, the 1/8 inch hole slows water circulation. I don't know why Jimmer's doesn't have that, it's supposed to be the reason it works to increase heat at idle. OTOH, if decreased circulation is the key, why use the raw water intake hose for the return instead of the engine's water pump?

Oh well, guess I'll hold off, at least until I understand this better. If my wife isn't complaining about being cold in the boat, it must not be a problem.

http://mccollister.info/yhole.jpg http://mccollister.info/yfitting.jpg
http://mccollister.info/ypump.jpg

88 PS190
11-30-2005, 11:44 AM
What if the key is increased circulation, and that if the Y connection didn't have a restriction barb there would be too much draw through the core and thereby produce either extreme heat, or too much draw on the hot water side.

The raw water pump moves alot of water very rapidly, I could see it being able to draw enough in excess of the other set up to require a restriction because at idle it could over cool the engine and thereby lower the temperature of the water and therefore the heat it could produce. As RPM go up suction rises, more water goes through the barb, and risk of over cooling diminishes.

This is purely speculation. But makes sense to me. The key then isn't less circulation, it is more circulation, just a matter of how much more the heater needs at idle.

jimmer2880
11-30-2005, 10:52 PM
....Supposedly, the 1/8 inch hole slows water circulation. I don't know why Jimmer's doesn't have that, it's supposed to be the reason it works to increase heat at idle. ....

Well then - maybe I'd better look closer at my Y adapter... . I don't remember looking through it. Hmmm... Maybe I do have the restriction hole.

I will say, though - that my Y is before the raw-water pump - not after (like you show in your pic BigMac).

sorry... can't go look at it either - I'm im Ottawa this week.

88 PS190
11-30-2005, 11:33 PM
the one in the pics above isn't on bigmacs boat i believe it is on a waterpump which the engine is rotating opposite of the MC such as perhaps the malibu

bigmac
12-01-2005, 12:22 AM
the one in the pics above isn't on bigmacs boat i believe it is on a waterpump which the engine is rotating opposite of the MC such as perhaps the malibu

Yeh, that's the same Johnson raw water pump as on a MC, but the image is not from a MasterCraft install. If you look at the hoses, you can see that the Y adapter is on the wire-reinforced intake hose, so it's before the raw water pump (you can even see a Perko Flush Pro on that line in the upper left corner of the image). I don't know if it's a Malibu - from what I read, Malibu's factory heater install puts the Y adapter after the raw water pump. FWIW, this thread (http://www.themalibucrew.com/forums/index.php?showtopic=492&hl=) on the Malibu forum indicates that it doesn't make TOO much difference in heat output, although the edge does go to HeaterCraft's recommendation.

Hard to know what to think. Putting the return line before the raw water pump should result in completely different flow characteristics than putting it afterward. Maybe none of it makes any difference - just get some hot water into the heater core - doesn't matter how you do it... :rolleyes:

AirJunky
12-01-2005, 12:48 AM
I believe the hole causes the hot water to stay in the heater core longer. Water passes thru the engine, and into the core & exhaust. The raw water pump is pulling the water thru the core, but because the hole is there, it causes the hot water to flow thru the core slower & allows a smaller amount of hot water to reenter the engine coolant.
Whatever... the bottom line is the heater pumps heat when the engine is at lower engine RPMs. And since I did the install 4 yrs ago, the only time I've ever seen my temp gauge get over about 180 or 185 was when the impeller blew apart (it was 3 yrs old).

bigmac
12-01-2005, 08:34 AM
I believe the hole causes the hot water to stay in the heater core longer. Water passes thru the engine, and into the core & exhaust. The raw water pump is pulling the water thru the core, but because the hole is there, it causes the hot water to flow thru the core slower & allows a smaller amount of hot water to reenter the engine coolant.
Whatever... the bottom line is the heater pumps heat when the engine is at lower engine RPMs. And since I did the install 4 yrs ago, the only time I've ever seen my temp gauge get over about 180 or 185 was when the impeller blew apart (it was 3 yrs old).

OK...but in this thread (http://www.themalibucrew.com/forums/index.php?showtopic=492&hl=) it seems that Malibu uses a Y pipe and puts it after the raw water pump, so it's not pulling water through the core, it should be pushing it since it's now on the output side of the raw water pump rather than the intake side. Although - there could be a venturi effect from the Y and 1/8 inch hole, in which case the concept should be similar in either location.

And then there's MasterCraft, which (currently, at least) doesn't use a Y pipe or raw water pump to pull or push at all, but uses the engine's water pump to circulate through the core instead. That has to be a lower volume of water, which in turn should accomplish the same thing as a restrictor hole on the Y pipe/raw water pump combo - decreased flow/more hot water time in the heater core. OR, one could just close down the valve on the intake manifold and slow the water flow that way. While more water-time in the core makes sense, one could (and they do) also argue that faster flow is the key, and that the suction applied by the raw water pump at the Y pipe accomplishes that - push AND pull the water instead of just pushing it, and the restrictor hole is there because that high-volume raw water pump is TOO powerful and pulls TOO much water.

I'm not trying to be argumentative for its own sake, I'm just trying to understand the rationale. I know you have extensive experience at cold-weather boating and I take your observations seriously. It looks like there are three different ways to get one's HeaterCraft heater to work. The plumbing arrangement that MasterCraft uses (on my boat) is basically the same as the way my truck works. I don't really want to go to the trouble of buying Y pipes, cutting hoses and scrunching down in the bilge of a V-drive for re-plumbing without understanding why I'm doing it.

Guess I gotta call Dan, Dan, the HeaterCraft man...

beef
12-01-2005, 11:16 AM
MC or Bu, the concept is the same. I do think the the greatest effect at idle is to put the Y before the rw pump - that's where I put mine.

Here's my take on the Y: At speed, the water flow is sufficient using the circulating pump for suction. However, at idle there is not enough to draw water through the core, so it cools off in between sets (when you need it for the guy that just got out of the lake!). Using the Y to hook up to the rwp definitely solves the idle speed problem. It has plenty of suction to circulate hot water through the core. My theory is that at higher speeds, the rwp would pull too much/too fast through the core, not allowing enough heat transfer. That's where the restriction hole comes in. The combination of the added suction of the rwp and the restriction in the pipe allows it to work better at all speeds.

Leroy
12-01-2005, 12:38 PM
I still want to talk to one of the ME's at work, but this page explains the why and importance of the restriction if used after the RW pump. Open the first yellow square to around 1/2 inch, pinch the second yellow square as small as you can. Not exactly the same as the Y but illustrates the principle.

This is also the same as why airplane wings have lift and pitchers can throw a curve ball..

http://home.earthlink.net/~mmc1919/venturi.html

Or why an atomizer works, actually better illustration.
http://theory.uwinnipeg.ca/mod_tech/node68.html

bigmac
12-01-2005, 12:44 PM
I still want to talk to one of the ME's at work, but this page explains the why and importance of the restriction if used after the RW pump. Open the first yellow square to around 1/2 inch, pinch the second yellow square as small as you can. Not exactly the same as the Y but illustrates the principle.

This is also the same as why airplane wings have lift and pitchers can throw a curve ball..

http://home.earthlink.net/~mmc1919/venturi.html

Or why an atomizer works, actually better illustration.
http://theory.uwinnipeg.ca/mod_tech/node68.html

Venturi effect is about the only way I can think that the Y adapter would work either before or after the RWP, and it also explains why there is a restriction on the return-line branch of the Y (if there were no restriction, there'd be no venturi effect). But if it is indeed venturi effect that makes the Y adapter work better, then that means that the point of the Y adapter is to increase heater core heat output by INCREASING water flow through the heater core.

Leroy
12-01-2005, 01:02 PM
Yes, agree, it increases the flow through the core. A simple T should not work well after the RW pump. See your point same before or after, but before there is a suction component also, which I assumed would dominate before the RW pump.

It's funny, this stuff always seems backwards to me, the way a wing is shaped should push the plane to the ground....until you understand.

Venturi effect is about the only way I can think that the Y adapter would work either before or after the RWP, and it also explains why there is a restriction on the return-line branch of the Y (if there were no restriction, there'd be no venturi effect). But if it is indeed venturi effect that makes the Y adapter work better, then that means that the point of the Y adapter is to increase heater core heat output by INCREASING water flow through the heater core.

Jorski
12-01-2005, 02:23 PM
The Y causes MORE water to be pulled through the core.

This is achieved by siphon effect. The cool water rushing through the fat part of the "Y" pulls hot water through the skinny part of the "Y". The reason that there is more heat at idle, is that the raw water intake line moves much more volume by the Y even at idle (via the siphon) than the motor's circulating pump does. At high speed, either connection pulls plenty of water

If more hot water is pulled through the core it will remain hotter per a given volume of air passing through the fins of the heater core. The air from the fan will cool the water in the core and thus the air will be warmed.

No voodoo...really just a clever and simple idea.

chico
12-04-2005, 01:15 PM
The restriction in the y is to throttle down the speed of the water going thru the core.
if you did not have that restriction there the raw water pump would rather suck water from the core than suck it all the way from the water intake,which would cause an overheat situation.(path of least resistance)At idle the circ pump doesn"t have enough pressure difference to force it thru the core.(too far away).

88 PS190
12-04-2005, 03:36 PM
ah but combined at idle the rw pulls on the output from the core, and the circ pump pushes it towards, and combined you have heat at idle so long as you have the Y.

bigmac
12-04-2005, 03:44 PM
If I detach the heater hose return line from the water circulating pump in order to hook it up to the Y, how do I plug that hole in the water pump?

rodltg2
12-04-2005, 04:19 PM
what did you do with the plug that was there?

88 PS190
12-04-2005, 04:53 PM
You should be able to get one at a hardware store

Its like a pipe threaded plug 3/8" or such. Bring the old adaptor, find something it threads in to in plumbing, and then find the plug. And then use teflon tape or silicon to seal it.

bigmac
12-04-2005, 05:26 PM
what did you do with the plug that was there?I left it at the MasterCraft factory.. :D

AirJunky
12-04-2005, 05:38 PM
If I detach the heater hose return line from the water circulating pump in order to hook it up to the Y, how do I plug that hole in the water pump?
Napa or the auto junkyard.

bigmac
12-04-2005, 05:59 PM
Napa or the auto junkyard.

I suppose I could have guessed that :o

Hollywood
12-27-2007, 04:55 PM
May be a little late to the party, but for you guys putting in the Y-adapters from a factory installation, you should be using a dissimilar plug on your circulation (water) pump. This will keep it from seizing up in there, not that you'll ever really need to remove it for any reason. Brass is readily available and would be best. Won't matter if you have an iron or aluminum casting, just like your engine drain plugs.

I agree with the theory of pulling MORE water through the core to keep the air blowing hot. Think of when your core gets clogged. If you were to plug the outlet, you would eventually get cool air blowing out because even though it is supplied with HOT water, the air blowing across it will cool down the water sitting in the core. A constant, flowing supply of hot water will keep your air blowing hot. The size of the hole in the Y is dependent on some fluid mechanic calculations someone else already did so no need to do it all over again.

Jesus_Freak
01-08-2008, 01:49 PM
This is achieved by siphon effect. The cool water rushing through the fat part of the "Y" pulls hot water through the skinny part of the "Y".

I am definitely late, but I wanted to expand a few concepts. The "siphon" or "venturi" effect is simply caused by a static pressure deficit when boundary layers become unattached from nearby walls. The sketch below is from some old, simple, and not-necessarily-related work I did. In the case of the heater system, material flowing from "B" induces a boundary layer separation at junction "C" and assists in pulling material from "A". This picture is based on material flowing via a different primary route, but the sketch is still valid.

I agree with the theory of pulling MORE water through the core to keep the air blowing hot. Think of when your core gets clogged. If you were to plug the outlet, you would eventually get cool air blowing out because even though it is supplied with HOT water, the air blowing across it will cool down the water sitting in the core. A constant, flowing supply of hot water will keep your air blowing hot.

Yes, the amount of heat the air can accept (you can feel) is 100% governed by UAdT. "U" is set by the air fan speed, since the heat transfer is limited by the gas-side exchange coefficient. "A" is set by the heater design. "dT" increases as more water is supplied at a given temperature. For a fixed design and fan speed, that is the ONLY way to get more heat.