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Old 05-02-2014, 22:31   #1
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Perkins 4-236 hot water heater hook up

Does anyone know definitively where to attach supply and return hot fresh water lines on a Perkins 4-236? I have an older circa 1988 model engine and newer models look a little different.
I will not been running the lines directly to the hot water heater but using a flat plate heat exchanger to save the save engine. In case of a major leak I can just shut off the valves to the small heat exchanger.
Thanks
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Old 07-02-2014, 16:55   #2
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Re: Perkins 4-236 hot water heater hook up

Bump:

I'm also interested in this question. I have a 4-108 and plan on installing a water heater next year. Information on how exactly to attach the heater to the engine cooler circuit is rather scarce, I've looked a couple of times. I think the 108 and 236 are fairly similar in coolant circuit and header tank layout.

-Argyle
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Old 07-02-2014, 17:27   #3
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Re: Perkins 4-236 hot water heater hook up

First of all you're never going to get water hotter than your engine cooling system.
Don't know aobut the 4-236, although it would probably work. On the 4-108 if you bypass the water cooled exhaust manifold on the engine circuit, add an additional pump and pipe it to your water heater. You'd have to run the pump anytime you're running the engine or the maifold will get too hot.
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Old 07-02-2014, 18:38   #4
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Re: Perkins 4-236 hot water heater hook up

From what I have read and experience with another boat (and engine) the hot water produced by extracting engine heat is much hotter almost scalding compared to the electric heat. A thermostatic mixing valve is always recommended to cool the water to safe levels before delivering it to the faucet.

So heat is not the issue at hand but exactly where the pickup and return lines attach to the fresh water cooling system of this particular engine or group of engines.

I got some information from TAD Engines on the east coast but can not decipher the photos from what I have. I could try to post those photos for others to look at. My engine appears different and therefore does not make sense. They sell a valve kit with barb fittings for a bit over $115.
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Old 07-02-2014, 19:20   #5
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Re: Perkins 4-236 hot water heater hook up

Domestic Hot water taps are always installed with the supply side above the thermostat, and the return side to the water pump.

Never take a supply from the block or the head, as that will be below the thermostat.

Return side is suction from the water pump. Supply is always above the thermostat. This only allows water to flow when the engine is up to operating temperature. A diesel engine is designed to run at operating temp...

Expect water temp in the tank to reach 180-190 degrees. So a thermal mixing valve is very prudent.

Lloyd

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Originally Posted by northwestsailor View Post
From what I have read and experience with another boat (and engine) the hot water produced by extracting engine heat is much hotter almost scalding compared to the electric heat. A thermostatic mixing valve is always recommended to cool the water to safe levels before delivering it to the faucet.

So heat is not the issue at hand but exactly where the pickup and return lines attach to the fresh water cooling system of this particular engine or group of engines.

I got some information from TAD Engines on the east coast but can not decipher the photos from what I have. I could try to post those photos for others to look at. My engine appears different and therefore does not make sense. They sell a valve kit with barb fittings for a bit over $115.
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Old 07-02-2014, 19:33   #6
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Re: Perkins 4-236 hot water heater hook up

On the Perkins engine I have worked on there has usually been a "tap" plug on the pressure side of the engine fresh water pump. This is where you tap off engine coolant to run through your hot water heater. The return usually always tee's into the hose line to the fresh water heat exchanger. The engine fresh water pumps I have seen "suck" engine coolant out of the engine block and then pump it to the heat exchanger. After being cooled in the heat exchanger the coolant is returned to the engine block to complete the cycle.
I use two ball valves at the engine end of each hose to the hot water heater so that I can isolate or shut off the 190F or so coolant from over-temping the hot water heater water. An automatic temperature regulator valve would be a fancier way to keep the water in the hot water heater from becoming too scalding to use.
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Old 07-02-2014, 19:46   #7
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Re: Perkins 4-236 hot water heater hook up

All taps on the Perkins water pumps are suction, The water pump, pumps through the block up into the head. The heat-ex is a closed circuit until the thermostat opens. This allows the engine to come up to operating temps.

When the t-stat opens the heat-ex then becomes part of the loop.

The 5/8 UNF parallel threaded openings are all above the t-stat, This is where the tem sender, temp alarm, and the domestic hot supply go.

The suction from the pump, can only pull when the t-stat is open.

Lloyd

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On the Perkins engine I have worked on there has usually been a "tap" plug on the pressure side of the engine fresh water pump. This is where you tap off engine coolant to run through your hot water heater. The return usually always tee's into the hose line to the fresh water heat exchanger. The engine fresh water pumps I have seen "suck" engine coolant out of the engine block and then pump it to the heat exchanger. After being cooled in the heat exchanger the coolant is returned to the engine block to complete the cycle.
I use two ball valves at the engine end of each hose to the hot water heater so that I can isolate or shut off the 190F or so coolant from over-temping the hot water heater water. An automatic temperature regulator valve would be a fancier way to keep the water in the hot water heater from becoming too scalding to use.
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Old 07-02-2014, 20:07   #8
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Re: Perkins 4-236 hot water heater hook up

Be wary of using "all" and "always" - invariably there are "exceptions" as in my Perkins engine. Having disassembled and rebuilt the engine and coolant system I know how mine works - yours and ones you have worked on may work differently - which is why I used the word "usually" rather than "all" or "always" As with most things nautical, there exists as many variations as there are sailors out there.
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Old 07-02-2014, 21:26   #9
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Re: Perkins 4-236 hot water heater hook up

Ok, now this gets more complicated. I am planning to add a hydronic boiler to my boat and I was hoping to get the boiler to preheat the engine when and if the boiler starts first.

I am not actually going to hook up the coolant directly to the hydronic circuit but via another flat plate heat exchanger so the possibility of total loss of engine coolant is slim.

Maybe I am a bit paranoid but I want to keep different coolant systems separate but hopefully work together when they can.
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Old 08-02-2014, 02:47   #10
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Re: Perkins 4-236 hot water heater hook up

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Originally Posted by northwestsailor View Post
Ok, now this gets more complicated. I am planning to add a hydronic boiler to my boat and I was hoping to get the boiler to preheat the engine when and if the boiler starts first.

I am not actually going to hook up the coolant directly to the hydronic circuit but via another flat plate heat exchanger so the possibility of total loss of engine coolant is slim.

Maybe I am a bit paranoid but I want to keep different coolant systems separate but hopefully work together when they can.
Maybe a silly question but how are you going to circulate the engine coolant that is heated by your proposed hydronic boiler flat plate heat exchanger - if the engine is not running?

However, you plan on doing it - I would only suggest staying away from your engine's raw water cooling system. Hot salty sea water can do a number on metal and other parts. Additionally, any alterations in the raw sea water system may alter the volume of raw water passing through your engine's system and then your rubber exhaust hose. Reducing the flow through the engine exhaust hose most probably will lead to failure of the rubber exhaust hose and a god-awful mess in your engine compartment or other spaces that the exhaust hose passes through.

It is common to only consider the consequences of reduced raw water flow as related to engine cooling temperature (e.g. overheating) - but more or at least as sensitive is the effect of reduced raw water flow on the rubber exhaust hose of insufficient cooling of the exhaust gases.
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Old 08-02-2014, 08:26   #11
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Re: Perkins 4-236 hot water heater hook up

Orsirisail, I am certainly not going to modify the raw water aspect of the cooling system. The way the hydronic heater works is to start the circulation pump first and monitor coolant temps. If below 140 then boiler is started. This would then heat the cabin coolant water to 180 or so. if the additional heat exchanger was placed below the pump I was planning on some advection heating and circulation would warm up the engine's coolant.
If it was directly into the block instead of the pump it seems it would be more effective.
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