I am moving my hot water heater to a new place under the V-berth. I am just wondering what kind of hose to use to extend the old lines to and from the engine to the heat exchanger in the hot water tank. The guy at West Marine said that most any kind of heater hose would be ok. I am not so sure about that. There must be some Coast Guard requirements. While I am at it, I am going to find out why this system has never worked in this boat (1992 Hunter 37.5 with a Yanmar 3HM35F engine). I can leave the dock with steaming hot water (electrically heated at the dock) and very soon, the water is much cooler if not cold. The existing system uses the secondary system from the engine to provide the water which goes to the hot water heat exchanger and then to an automotive type air heater. I am considering replumbing the main heat exchanger and sending the engine hot water which normally goes to that heat exchanger and instead sending it first to the hot water heat exchanger/air heater circuit in the bow. I must admit that I haven't recently looked at this stuff physically so am not sure about hose sizes, connections, etc.
Engine hot water hose / cooling system questions
- Thread starter patrick
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Patrick, some info,,
Don't believe the WM talking head on this one. I used Gates hose from the engine to the hot water heat exchanger. The ID was only 5/8" but the OD was larger than 3/4" hose. It's also printed on the hose that it's marine grade. But it's your call. If you will have access to the hose for replacement purposes then any hose will do. I would be sure in that case, to have a thought-out emergency repair. As far as your heat exchanger, it sounds like it's working perfectly. Remember, heat exchanging works both ways. When you start a cold engine with one of these systems, the heat in your water heater is drawn off by the cold coolant in the engine. It comes back later of course. Maybe a shut-off valve would be the answer for your application. Again, it depends.
Don't believe the WM talking head on this one. I used Gates hose from the engine to the hot water heat exchanger. The ID was only 5/8" but the OD was larger than 3/4" hose. It's also printed on the hose that it's marine grade. But it's your call. If you will have access to the hose for replacement purposes then any hose will do. I would be sure in that case, to have a thought-out emergency repair. As far as your heat exchanger, it sounds like it's working perfectly. Remember, heat exchanging works both ways. When you start a cold engine with one of these systems, the heat in your water heater is drawn off by the cold coolant in the engine. It comes back later of course. Maybe a shut-off valve would be the answer for your application. Again, it depends.
Choices ...
I'm not sure what you mean by "secondary system", I'll assume that you mean the raw water side rather than the engine side. In the raw water system cool/cold sea water is pumped through the heat exchanger then into the exhaust and overboard. The should never get very hot, certainly not hot enough to be of any use to heat the boat or the water tank. The engine system is closed and under pressure. The engine temperature is controlled by the thermostat and the coolant is plenty hot enough for heating the boat and water. The hose going from the engine into the heat exchanger is where your heaters should be. Go from the engine to the hot water tank first, then to the boat heater then back to the heat exchanger. This gives the water heater the warmest water and slightly cooler water to the boat heater (until the water in the tank is up to temp). When the system is fully warmed up, the temp will be about the same everywhere. The whole system will be under pressure, so good hoses and proper clamps are needed. I'm not aware of any USCG requirements for heater hose. Normal, high quality, reinforced heater hose should be fine. Keep it out of the bilge and route it to minimize chafe and so you can inspect connections. Adding a diesel fired water heater to the system would give you hot water and heat at anchor as well as at the dock.
I'm not sure what you mean by "secondary system", I'll assume that you mean the raw water side rather than the engine side. In the raw water system cool/cold sea water is pumped through the heat exchanger then into the exhaust and overboard. The should never get very hot, certainly not hot enough to be of any use to heat the boat or the water tank. The engine system is closed and under pressure. The engine temperature is controlled by the thermostat and the coolant is plenty hot enough for heating the boat and water. The hose going from the engine into the heat exchanger is where your heaters should be. Go from the engine to the hot water tank first, then to the boat heater then back to the heat exchanger. This gives the water heater the warmest water and slightly cooler water to the boat heater (until the water in the tank is up to temp). When the system is fully warmed up, the temp will be about the same everywhere. The whole system will be under pressure, so good hoses and proper clamps are needed. I'm not aware of any USCG requirements for heater hose. Normal, high quality, reinforced heater hose should be fine. Keep it out of the bilge and route it to minimize chafe and so you can inspect connections. Adding a diesel fired water heater to the system would give you hot water and heat at anchor as well as at the dock.
water heater hookup
Before plumbing the water heater in line with the heat exchanger you might want to look at this info. http://sankaty.homestead.com/water_heater_hook_ups.html http://sankaty.homestead.com/waterheatercircuituniversal5432.html
Before plumbing the water heater in line with the heat exchanger you might want to look at this info. http://sankaty.homestead.com/water_heater_hook_ups.html http://sankaty.homestead.com/waterheatercircuituniversal5432.html
Nice Links!
Richard - Great Links! I looked at the Espar site, they used to have a nice cooling schematic, but I could not find it. I'm not a big fan of the Type 1 systems, the added volume in the bypass circuit will slow down engine warm-up. Getting the engine and oil up to temp quickly has a great effect on engine life. I can see potential problems with running the heaters in series with the heat exchanger if hose size has to be reduced for either heater. Having bypass valves and the two heaters in parallel is the best option, the flow to each component can be adjusted. This would be more important on a power boat where engine overheating could be a problem. On a sailboat, I want hot water for a shower with minimum run time. Certainly in the time it takes to recharge the house bank. I don't really see the use of a hot water cabin heater on a sailboat, unless there is a fuel fired water heater in the system also. I'm not going to run the engine all night to keep the cabin warm.
Richard - Great Links! I looked at the Espar site, they used to have a nice cooling schematic, but I could not find it. I'm not a big fan of the Type 1 systems, the added volume in the bypass circuit will slow down engine warm-up. Getting the engine and oil up to temp quickly has a great effect on engine life. I can see potential problems with running the heaters in series with the heat exchanger if hose size has to be reduced for either heater. Having bypass valves and the two heaters in parallel is the best option, the flow to each component can be adjusted. This would be more important on a power boat where engine overheating could be a problem. On a sailboat, I want hot water for a shower with minimum run time. Certainly in the time it takes to recharge the house bank. I don't really see the use of a hot water cabin heater on a sailboat, unless there is a fuel fired water heater in the system also. I'm not going to run the engine all night to keep the cabin warm.
This May Help
Here is a pic of my 3HM35F. You will see the hose with the green stripe on the top of the engine. There is also one behind it out of view. The green disc is the hot water sensor for the control panel light/alarm. Follow the pair of hoses down by the alternator and they head over to the water heater under the galley (one is output, the other is input on the heater). This is a tap into the closed engine cooling system and heats the water in the water heater when running. Mine is an '88 Legend 37 and has never had a problem heating the water.
Here is a pic of my 3HM35F. You will see the hose with the green stripe on the top of the engine. There is also one behind it out of view. The green disc is the hot water sensor for the control panel light/alarm. Follow the pair of hoses down by the alternator and they head over to the water heater under the galley (one is output, the other is input on the heater). This is a tap into the closed engine cooling system and heats the water in the water heater when running. Mine is an '88 Legend 37 and has never had a problem heating the water.
Are there CG standards for coolant hose?
It looks like my system is a type 3. There are as I recall two sets of hose connections on the engine side or three if you count the short bypass hose. One set (I will call the primary circuit) is connected to the main heat exchanger for cooling the engine. It seems to work fine. The engine rarely has overheated and then it was because of eel grass in the water filter so I assume that it is ok. The second set of engine coolant connections (secondary circuit) appears to be for the hot water heat exchanger and or the hot water (auto type) air heater. This secondary circuit is connected just like Paul Akers describes. As to hot water tank and air heater, mine are in series in the forward part of the boat under the port settee next to the bulkhead which forms the V-berth wall. The hose from the engine to the hot water tank is 5/8 inch and it is adapted to 1/2 inch hose for connection to the air heater core and then back to 5/8 inch again for the return run. The air from the heater is warm under way but only warm not hot like in the car. The hot water is much cooler under way than at the dock. The engine seems to take a long time to warm up but then it seems to be quite warm enough to produce heat for the hot water systems but it does not seem to get it there. I have checked the thermostat and it is good. I have bled the lines and there seems to be no air in the circuit. As I recall, the water does not cycle through either the primary heat exchanger or the hot water heater when the thermostat is closed. When the thermostat opens, it allows coolant to flow into both circuits. I am wondering if there is just too much distance from the engine to the heater or if there is too much restriction in the flow of coolant. Could I add a "boost pump" to the line? Would a hotter thermostat help the problem? Could I somehow restrict the flow into the primary heat exchanger to cause the hot water to go to the hot water heater? Should I use larger heater hose?
It looks like my system is a type 3. There are as I recall two sets of hose connections on the engine side or three if you count the short bypass hose. One set (I will call the primary circuit) is connected to the main heat exchanger for cooling the engine. It seems to work fine. The engine rarely has overheated and then it was because of eel grass in the water filter so I assume that it is ok. The second set of engine coolant connections (secondary circuit) appears to be for the hot water heat exchanger and or the hot water (auto type) air heater. This secondary circuit is connected just like Paul Akers describes. As to hot water tank and air heater, mine are in series in the forward part of the boat under the port settee next to the bulkhead which forms the V-berth wall. The hose from the engine to the hot water tank is 5/8 inch and it is adapted to 1/2 inch hose for connection to the air heater core and then back to 5/8 inch again for the return run. The air from the heater is warm under way but only warm not hot like in the car. The hot water is much cooler under way than at the dock. The engine seems to take a long time to warm up but then it seems to be quite warm enough to produce heat for the hot water systems but it does not seem to get it there. I have checked the thermostat and it is good. I have bled the lines and there seems to be no air in the circuit. As I recall, the water does not cycle through either the primary heat exchanger or the hot water heater when the thermostat is closed. When the thermostat opens, it allows coolant to flow into both circuits. I am wondering if there is just too much distance from the engine to the heater or if there is too much restriction in the flow of coolant. Could I add a "boost pump" to the line? Would a hotter thermostat help the problem? Could I somehow restrict the flow into the primary heat exchanger to cause the hot water to go to the hot water heater? Should I use larger heater hose?
Patrick, a couple more questions.
We haven't talked about time. How long are you running your engine? It has to do some sort of 'work' to generate enough waste heat for the H/W heater in a fairly sort time. In other words, just idling at anchor for a half hour in the morning won't do it. Also, how big is your water heater. Six gallons doesn't take as long to heat up as,,, Aw hell, you know that.
We haven't talked about time. How long are you running your engine? It has to do some sort of 'work' to generate enough waste heat for the H/W heater in a fairly sort time. In other words, just idling at anchor for a half hour in the morning won't do it. Also, how big is your water heater. Six gallons doesn't take as long to heat up as,,, Aw hell, you know that.
Fred, to answer your questions
I usually run the engine for a couple of hours under way if I expect it to generate any hot water. It takes about a half hour idling at the dock to get barely warmed up. The water heater is 6 gallons and the automotive type of air heater core is a typical large car size with one 5 inch fan blowing through it.
I usually run the engine for a couple of hours under way if I expect it to generate any hot water. It takes about a half hour idling at the dock to get barely warmed up. The water heater is 6 gallons and the automotive type of air heater core is a typical large car size with one 5 inch fan blowing through it.
low hot water heat???
Patrick, is it possible that you are cooling the engine water with the air exchanger so much that it's too cool to transfer enough heat in the water heater??? there may just not be enough waste heat from your engine to run both. try bypassing the air exchanger and see if that improves the hot water
Patrick, is it possible that you are cooling the engine water with the air exchanger so much that it's too cool to transfer enough heat in the water heater??? there may just not be enough waste heat from your engine to run both. try bypassing the air exchanger and see if that improves the hot water
Chuck, you might be on to something
I just assumed that the air heater was installed on the return side of the circuit but I must admit that I have not actually verified that. I am not sure which connection on the engine is which and which hose is which at the other end. Maybe it will be obvious when I get to the boat. If the air heater is first in the circuit ie: the hot side, that combined with the reduction to 1/2 inch pipe might just account for the problem with lack of heat. Embarrassing as that might be, I will let you know in a few days. Maybe I should move the water heater aft instead of forward and thus closer to the galley area and the engine. Thoughts on that??? Thanks a lot guys. This gives me some hope on a problem which has been plaguing me for years. Still no answer to my hose standards question though ...
I just assumed that the air heater was installed on the return side of the circuit but I must admit that I have not actually verified that. I am not sure which connection on the engine is which and which hose is which at the other end. Maybe it will be obvious when I get to the boat. If the air heater is first in the circuit ie: the hot side, that combined with the reduction to 1/2 inch pipe might just account for the problem with lack of heat. Embarrassing as that might be, I will let you know in a few days. Maybe I should move the water heater aft instead of forward and thus closer to the galley area and the engine. Thoughts on that??? Thanks a lot guys. This gives me some hope on a problem which has been plaguing me for years. Still no answer to my hose standards question though ...
Hose Standards
I've looked through my copy of standards for small vessels and cannot find a standard for water/heater hose. The standards for fuel and wet exhaust hose are for safety. I guess they don't consider a blown heater hose a fire risk ... I'd go with a wire reinforced thick wall hose (Gates makes some). The tougher and thicker the hose the less chance that it will be damaged from chafe or gear dropping on it. A thick wall will radiate less heat.
I've looked through my copy of standards for small vessels and cannot find a standard for water/heater hose. The standards for fuel and wet exhaust hose are for safety. I guess they don't consider a blown heater hose a fire risk ...
I'd go with a wire reinforced thick wall hose (Gates makes some). The tougher and thicker the hose the less chance that it will be damaged from chafe or gear dropping on it. A thick wall will radiate less heat.- Status