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Old 08-12-2019, 17:12   #1
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Use engine water intake for heat pump?

In a effort to reduce the holes I put in my hull, especially in her neither regions, could I use the through hull for the water intake for the engine for the heat pump as well? What type of fitting/through hull would I use for this?


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Old 08-12-2019, 17:46   #2
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Re: Use engine water intake for heat pump?

I personally would not tee anything off the engine water intake.
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Old 08-12-2019, 17:49   #3
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Re: Use engine water intake for heat pump?

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Originally Posted by gonesail View Post
I personally would not tee anything off the engine water intake.
Intake for the head then?
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Old 08-12-2019, 18:35   #4
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Re: Use engine water intake for heat pump?

Sharing a thru hull probably cause more trouble than having an extra thru hull if properly installed. Existing thru hulls were probably sized to the application and running an additional item starves both for water.
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Old 08-12-2019, 19:52   #5
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Re: Use engine water intake for heat pump?

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Originally Posted by Lepke View Post
Sharing a thru hull probably cause more trouble than having an extra thru hull if properly installed. Existing thru hulls were probably sized to the application and running an additional item starves both for water.
Even if it's just the fresh water for the toilet?
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Old 08-12-2019, 20:07   #6
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Re: Use engine water intake for heat pump?

Having a boat with a proper seachest, I can tell you that they DO work, and you can tee off the engine intake thru-hull without problems. Many good boats are designed this way, and they work. On my boat one thruhull feeds the engine, the genset, the water maker, and two AC cooling pumps. Sister ships that used electric toilets also feed those from the same thruhull.

BUT.... You need to understand a the issues and design needs for a system like this.

The thru-hull needs to be large enough to supply all the possible users at one time. If you don't have a custom seachest, a large strainer sufficient to feed all the users and a manifold of tees and valves can work just as well.

If you use a simple manifold, you should have a separate valve for each user so you can isolate each one for maintenance without shutting the whole system down.

You need to be sure than none of the users can pull water "backwards" through the other systems. An engine's flexible impeller water pump is close enough to a positive displacement pump that it will not back flow to any real extent, but a heat pump's centrifugal pump would need a check valve. In my system the engine and genset have pumps that prevent back flow, as does the watermaker. But the AC pumps each have a check valve to prevent air bleeding back into the system.

It is not a simple change. It is worth doing if done well, but it done badly it will be an endless source of problems.

People who dismiss the benefits of limiting the number of thru hulls have never opened a companionway and seen water over the floor boards. I have seen boats with more than a dozen underwater thru hull fittings (record on a 53 foot boat: 23!). I would not even waste time trying to figure out WHICH one was the issue, I'd just call a mayday and launch the life raft.
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Old 08-12-2019, 20:15   #7
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Re: Use engine water intake for heat pump?

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Originally Posted by billknny View Post
Having a boat with a proper seachest, I can tell you that they DO work, and you can tee off the engine intake thru-hull without problems. Many good boats are designed this way, and they work. On my boat one thruhull feeds the engine, the genset, the water maker, and two AC cooling pumps. Sister ships that used electric toilets also feed those from the same thruhull.

BUT.... You need to understand a the issues and design needs for a system like this.

The thru-hull needs to be large enough to supply all the possible users at one time. If you don't have a custom seachest, a large strainer sufficient to feed all the users and a manifold of tees and valves can work just as well.

If you use a simple manifold, you should have a separate valve for each user so you can isolate each one for maintenance without shutting the whole system down.

You need to be sure than none of the users can pull water "backwards" through the other systems. An engine's flexible impeller water pump is close enough to a positive displacement pump that it will not back flow to any real extent, but a heat pump's centrifugal pump would need a check valve. In my system the engine and genset have pumps that prevent back flow, as does the watermaker. But the AC pumps each have a check valve to prevent air bleeding back into the system.

It is not a simple change. It is worth doing if done well, but it done badly it will be an endless source of problems.

People who dismiss the benefits of limiting the number of thru hulls have never opened a companionway and seen water over the floor boards. I have seen boats with more than a dozen underwater thru hull fittings (record on a 53 foot boat: 23!). I would not even waste time trying to figure out WHICH one was the issue, I'd just call a mayday and launch the life raft.


That's inline with what I was thinking. Any guides on design and calculations?

Thanks!
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Old 08-12-2019, 22:58   #8
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Re: Use engine water intake for heat pump?

Quote:
Originally Posted by billknny View Post
Having a boat with a proper seachest, I can tell you that they DO work, and you can tee off the engine intake thru-hull without problems. Many good boats are designed this way, and they work. On my boat one thruhull feeds the engine, the genset, the water maker, and two AC cooling pumps. Sister ships that used electric toilets also feed those from the same thruhull.

BUT.... You need to understand a the issues and design needs for a system like this.

The thru-hull needs to be large enough to supply all the possible users at one time. If you don't have a custom seachest, a large strainer sufficient to feed all the users and a manifold of tees and valves can work just as well.







If you use a simple manifold, you should have a separate valve for each user so you can isolate each one for maintenance without shutting the whole system down.

You need to be sure than none of the users can pull water "backwards" through the other systems. An engine's flexible impeller water pump is close enough to a positive displacement pump that it will not back flow to any real extent, but a heat pump's centrifugal pump would need a check valve. In my system the engine and genset have pumps that prevent back flow, as does the watermaker. But the AC pumps each have a check valve to prevent air bleeding back into the system.

It is not a simple change. It is worth doing if done well, but it done badly it will be an endless source of problems.

People who dismiss the benefits of limiting the number of thru hulls have never opened a companionway and seen water over the floor boards. I have seen boats with more than a dozen underwater thru hull fittings (record on a 53 foot boat: 23!). I would not even waste time trying to figure out WHICH one was the issue, I'd just call a mayday and launch the life raft.
+1

Fitted many sea chests or manifolds to boats It simplifies life immensely One sea-cock and one strainer and no headaches. 2" is more than enough for most boats up to 60'
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Old 09-12-2019, 09:58   #9
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Re: Use engine water intake for heat pump?

Only issue I would see with the sea chest or manifold idea is that I like to have two inlets for the engine. This is because the engine intake take quite a bit of water continuously and I have seen problems where debris such as plastic bags have covered the intake and the suction holds them in place. A second intake makes this unlikely as you don't get the increased suction. The ideal would be one intake each side to a manifold that distributes to services as required. Generally outlets have to be individual to prevent back flow/cross contamination.
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Old 09-12-2019, 12:13   #10
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Re: Use engine water intake for heat pump?

Quote:
Originally Posted by billknny View Post
Having a boat with a proper seachest, I can tell you that they DO work, and you can tee off the engine intake thru-hull without problems. Many good boats are designed this way, and they work. On my boat one thruhull feeds the engine, the genset, the water maker, and two AC cooling pumps. Sister ships that used electric toilets also feed those from the same thruhull.

BUT.... You need to understand a the issues and design needs for a system like this.

The thru-hull needs to be large enough to supply all the possible users at one time. If you don't have a custom seachest, a large strainer sufficient to feed all the users and a manifold of tees and valves can work just as well.

If you use a simple manifold, you should have a separate valve for each user so you can isolate each one for maintenance without shutting the whole system down.

You need to be sure than none of the users can pull water "backwards" through the other systems. An engine's flexible impeller water pump is close enough to a positive displacement pump that it will not back flow to any real extent, but a heat pump's centrifugal pump would need a check valve. In my system the engine and genset have pumps that prevent back flow, as does the watermaker. But the AC pumps each have a check valve to prevent air bleeding back into the system.

It is not a simple change. It is worth doing if done well, but it done badly it will be an endless source of problems.

People who dismiss the benefits of limiting the number of thru hulls have never opened a companionway and seen water over the floor boards. I have seen boats with more than a dozen underwater thru hull fittings (record on a 53 foot boat: 23!). I would not even waste time trying to figure out WHICH one was the issue, I'd just call a mayday and launch the life raft.

No they don't all go to one fitting. That one fitting feeds the tank (sea chest) That sea Chest is exactly that, it is a container that is fed by one thru hull, but all those feeds your talking about go into the sea chest, not one hose feeding one thing. The side of the sea chest is just like different locations on the hull but in one location. Not remotely like tying two or three hoses together on a single hose.
If you doubt me. Go to your hose feeding your engine cooling. Cut it in two add your a/c pump hose, down a couple inches, cut it again and add a t for your gen set. I will bet my ass none of your equipment will work and cool properly.
As for an answer for the original question, no, do not put any other equipment on the engine coolant hose.
The hose for the exchanger your talking about uses copious water flow, I definitely put it on a dedicated thru hull. I never recommend sharing of thru hulls. Capt. Vince Rakstis, Ret. St.Petersburg, Fl.
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Old 09-12-2019, 13:30   #11
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Re: Use engine water intake for heat pump?

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Originally Posted by NorthernMac View Post
In a effort to reduce the holes I put in my hull, especially in her neither regions, could I use the through hull for the water intake for the engine for the heat pump as well?
Benefit of doing this is less about fewer hull penetrations as modern seacocks are very reliable, but more about having a single sea strainer which takes up an enormous amount of real estate. Down side is its arguably more likely to clog a single sea strainer, so make sure its easily viewable.

Option 1 - off shelf. Try the Groco manifold. Groco warns against using them, but makes them if you insist on doing it anyway. Note, the largest manifold port is smaller than the intake. They make several sizes.

Option 2 - build your own. Attached pic is a nicely installed one that I plucked off Steve D'Antonio's website. He does not give any design guidance, but I designed mine such that the sum of the area of simultaneous consumers equal to or is less than intake (area of a circle is PI * r ^2). For example, my Perkins 4.236 has a 1-inch intake for engine, and A/C has 3/4" intake. Therefore, I can use a 1-1/4" intake to feed these two simultaneously. If I also had a generator with 3/4" intake, I would need a 1-1/2" intake. Appears Groco follows this same approach. I will say that engine + generator + A/C feels like it's pushing the concept a bit - any obstruction in the Sea Strainer would cause contention.

NOTE - new engine manufacturers may void a warranty if the engine does not have a dedicated feed. Also, a surveyor may ding you, especially if you do not size it properly.

Click image for larger version

Name:	Manifold <a title=Bronze.jpg Views: 49 Size: 369.5 KB ID: 204698" style="margin: 2px" />
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Old 12-12-2019, 10:27   #12
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Re: Use engine water intake for heat pump?

My Tayana 47 came with a large sea strainer that serviced several items, but it was 20 years old and made of Chinese stainless that seemed on the verge of failing, so I replaced it with a HUGE (about 10" diameter X 12" tall) Groco strainer coupled to a manifold that looks much like the one in the previous post. Each item has it's own shutoff valve so each can be isolated. I have my engine, my genset, and my raw water washdown pump supply on this one one strainer and have had no problems. I'm sure I could add the heat pump or water maker but would want to have check valves so the engine wouldn't suck water out of them. 99% of the time, it's just the engine or the generator that is using this water supply, and I feel that having such a big strainer relative to the engine sizes helps ensure that it would take quite a lot of time (enough so I'd hopefully notice) for it to clog to the point of restricting flow to the engine(s). I considered adding the supply for refrig and heat pump as well as the watermaker to this manifold but that would have made for an even larger manifold that I didn't have room for so it was easier to keep them on 2 other nearby thru-hulls. But I like the idea of eliminating holes in the bottom of my boat as much as possible.
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Old 12-12-2019, 11:04   #13
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Re: Use engine water intake for heat pump?

I'm a real fuss-budget when it comes to adding throughhulls. I have two. One is sewage pumpout (not sewage gravity feed) and stays closed. The other does everything else that needs raw water (engine cooling, genset cooling, water maker, salt water wash down). That one can be closed by pulling a wire in the main salon above the engine room.

I met a Nordhaven owner who said he had 27 seacocks. Nordhaven? Those guys build blue water boats. No. This is one of the reasons I decided to build my own - seacocks under engines and other places I would never get to them if one popped. Remember: When a seacock is open, the entire inside surface of it and its attendent hoses is part of your hull. That's all that keeping the water out.
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