Using Genny (NL 6kw) Coolant Loop to Heat Water?

[staylucky]

has anyone connected the coolant loop of a 6kw northern lights generator to the hot water heater?

i would like to run the generator mornings and evenings while at anchor for a short period - say 2 hours - during which i would charge batteries and run other appliances. this is more realistic if i use the generator's waste heat to heat water.

i know this is commonly done with the main engine, but not as often the generator. it's been suggested to me that it would prevent such a small generator from reaching and holding operating temperature.

has anyone done this with a 6kw northern lights, or other small generator?

thanks,

chris

[smac999]

how much other load are you putting on it? why not just run the electric water heater?




with 6k I would think you can run a big charger, water heater, and other things. you want it loaded up anyways.

[GordMay]

Greetings and welcome aboard the CF, Chris.

[HappyMdRSailor]

Originally Posted by smac999

how much other load are you putting on it? why not just run the electric water heater?

with 6k I would think you can run a big charger, water heater, and other things. you want it loaded up anyways.

Sounds like the most logical direction... But then he doesn't have enough juice to run the disco ball and DJ system???

Welcome to CF Chris !

[GordMay]

Good question for a dealer
➥ Dealers | Northern Lights Marine Generators

[Trim50]

I did this with my 3.5kw genny...works pretty good, but take awhile to heat 10 gallon tank.

[staylucky]

thanks for the welcome, been reading reading tons of posts and learned a lot - it's a great forum.

> why not just run the electric water heater?

i could, and it might be the answer. it would require running the generator a little longer twice a day. i don't know exactly how much longer, it would be a function of hot water use mostly, i would think. even without the heating element, the 6kw generator will be max'ed out (i'd shoot for 80-85% load) for about two hours twice a day. those disco balls use a lot of power. jk, i put the loads in a spreadsheet and it's pretty maxed out: battery charging, a/c, cooking, icemaker, watermaker, miscellaneous...

> what does northern lights say?

they're the ones who said the generator wouldn't get or stay hot enough ;-) before i give up i am hoping someone here has real life experience to the contrary. i would think the ambient water temperature would be a big factor, maybe it would work better in florida than maine? the boat will be in florida.

[LakeSuperior]

Originally Posted by smac999

how much other load are you putting on it? why not just run the electric water heater?

Then you are not recovering the energy (heat) that is wasted via the heat exchange with the sea water. You have to put more fuel in (the inefficient side thus consuming more fuel per hour (for sure a minor consideration) to run the hot water heater.

If you put the hot water heater in the internal NL loop you will have to put it on the down side of the thermostat. Now, less heat is lost to the sea water. The thermostat will regulate the coolant temperature to the block and head. So in general your NL generator will not run cold.

[roland stockham]

There is no problem with engine temp as the take off for the water heating should be after the thermostat so if engine temp is low no water flows to the heater. As a goo rule of thumb an engine produces about the same power as heat to the water as it does to the output shaft. So 6Kw of electric = 6Kw of water heating. This is fine if the geny is running hard but if you are only running a 50a charger that's about 800w load you get a lot less heat. You can boost this by adding a heat exchange to the exhaust as well and it will double the heat output. Same rules apply to the main engine, it's the load that creates heat rather than the engine size although bigger engines have more losses when idling so more waste heat.
A good solution is to do both, connect the water system but then turn on the electric heater. This adds a high load to the geny which is better for it and produces an equal amount of waste heat so you can heat the tank in half the time.

[mainesail]

Wow, that's alot of running-your neighbors will love you-NOT.

I suggest you read the Dashews works. Not sure if they are still sailing, but they are extremely experienced sailors and cruisers and meticulously refine their systems and procedures for efficiency and reliability. They developed their systems to maximum efficiency, high efficiency alternator, using cooling water for heat, highly insulated icebox to really holds the cold, big battery bank capacity etc.-all to minimize the time needed to take care of system demands, while living in comfort anywhere in the world.
I must also mention the damage that many folks do to their engines while running them at low loads for long hours.
Not sure why you feel the need for a genset, but if you do the above, maybe you can toss it, but PLEASE PLEASE do not think it is a good idea to run any engine at anchorage for hours.

[LakeSuperior]

Originally Posted by roland stockham

There is no problem with engine temp as the take off for the water heating should be after the thermostat so if engine temp is low no water flows to the heater. As a goo rule of thumb an engine produces about the same power as heat to the water as it does to the output shaft. So 6Kw of electric = 6Kw of water heating. This is fine if the geny is running hard but if you are only running a 50a charger that's about 800w load you get a lot less heat. You can boost this by adding a heat exchange to the exhaust as well and it will double the heat output. Same rules apply to the main engine, it's the load that creates heat rather than the engine size although bigger engines have more losses when idling so more waste heat.
A good solution is to do both, connect the water system but then turn on the electric heater. This adds a high load to the geny which is better for it and produces an equal amount of waste heat so you can heat the tank in half the time.

Actually, the rule of thumb is 1/3 power to the shaft, 1/3 waste heat to coolant, and 1/3 to exhaust gas.

[leftbrainstuff]

Originally Posted by staylucky

has anyone connected the coolant loop of a 6kw northern lights generator to the hot water heater?

i would like to run the generator mornings and evenings while at anchor for a short period - say 2 hours - during which i would charge batteries and run other appliances. this is more realistic if i use the generator's waste heat to heat water.

i know this is commonly done with the main engine, but not as often the generator. it's been suggested to me that it would prevent such a small generator from reaching and holding operating temperature.

has anyone done this with a 6kw northern lights, or other small generator?

thanks,

chris

We use our 6kW Kubota generator to heat hot water.

I monitored temps on both raw water and the closed loop coolant circuits and sized the bypass to maintain non cavitating flow and flowrate to maximise heat transfer.

The thermostat maintains the closed loop coolant circuit and fast warmup is unaffected.

It takes about an hour and 20 minutes to heat our 6 gallon hot water.

Sent from my SM-N900T using Cruisers Sailing Forum mobile app

[Blue Stocking]

Basically, all you are doing is putting a large header tank on your closed circuit cooling side.

[Mystic38]

to the OP, personally i think the electric water heater is the best and simplest idea.. gives you solid load management of the genny... charger, cooker etc for first hour then heater on when stove is off.



I suspect the Dashews work is largely irrelevant here as op has a power boat.. electrically and systems wise they are chalk and cheese to a sailboat... and largely speaking a generator is a requirement for the domestic ac fridge/freezers, electric stove, ice-makers, and even ac water pumps are not uncommon..

He indicates running at target of 85% load so there is no issue with gen load and running times..its his diesel

regards

Originally Posted by mainesail

Wow, that's alot of running-your neighbors will love you-NOT.

I suggest you read the Dashews works. Not sure if they are still sailing, but they are extremely experienced sailors and cruisers and meticulously refine their systems and procedures for efficiency and reliability. They developed their systems to maximum efficiency, high efficiency alternator, using cooling water for heat, highly insulated icebox to really holds the cold, big battery bank capacity etc.-all to minimize the time needed to take care of system demands, while living in comfort anywhere in the world.
I must also mention the damage that many folks do to their engines while running them at low loads for long hours.
Not sure why you feel the need for a genset, but if you do the above, maybe you can toss it, but PLEASE PLEASE do not think it is a good idea to run any engine at anchorage for hours.

[staylucky]

thanks for the thoughtful responses.

maybe it's best to keep things simple and use the electric heating element, esp if northern lights recommends against using the coolant looop. i was just curious to know if anyone had any real world experience.

i tried to be conservative w my calcs, generator run times might be less than 2 hours. the northern lights 6kw generator has a factory sound enclosure and with a muffler and gen-sep i won't be 'that guy' in an anchorage.