Using Generator Cooling to Heat Water

[moseriw]

maybe practical but tricky as usually the engine is connected to the boiler. In this case you mix engine coolant with genset coolant.
Safe and easier way: use another boiler if you have room enough.

[Locquatious]

We looked into that with our Northern Lights generator, which probably has the same block engine. That is, when you look up parts for the NL, matching Perkins and Kubota parts show up.
Northern Lights and the local NL service manager did not recommend it. They say that generators should run hard and hot to avoid carbon build-up especially in the exhaust. They recommended keeping the generator at full load, using the electric water heater to add load as the battery load drops. They recommended running air conditioning to add load, even if you don't want the cool, toward the end of the battery charging cycle.
Besides, they said it would void the warranty.

[Oohla]

Marine antifreeze is propylene glycol which is relatively non-toxic. It can be used in food products.


Automotive antifreeze is ethylene glycol and it highly toxic.

[rslifkin]

Originally Posted by Oohla

Marine antifreeze is propylene glycol which is relatively non-toxic. It can be used in food products.


Automotive antifreeze is ethylene glycol and it highly toxic.

Propylene glycol is the stuff used for winterizing. Most marine engines with closed circuit cooling use automotive type ethylene glycol in the closed cooling loop.

[bclaude]

All good points, thank you. My main issue is that when we are in relatively cold/cool weather, it takes forever to get enough hot water for a shower and that's when we need it most. Intellectually it irks me to dump all that hot water in the ocean while I wait for... hot water. I am not sure what the volume of my calorifier is but I have replaced the 1kW immersion heater by a 2kW and it still takes a long time. Also when I start my generator is when I have maximum load: Water heater, Max draw from the battery chargers and water maker. At this time, my loads are such that most of the time; I must wait for the battery chargers to taper off before I can turn my water maker on. My generator is insufficient to do it all at the same time when the battery chargers are in the bulk phase of the charge cycle. If I ever was in a situation where the generator does not produce enough heat because of insufficient load then nothing keeps me from turning on the electric immersion heater and the problem will take care of itself and I will get hot water that much quicker. As Sailmonkey said, the biggest issue that I see is the 5 to 6m round trip and make sure I do not create a water lock anywhere in the loop My thinking is that I will give it a try and observe the generator temperature closely when it is a full load. In any event the generator has a high temperature kill switch so if I am careful, I don't see how I could damage it. Since I have a 2nd coil in my water heater, the investment will be very low and reversing course should be easy. I will need to identify the thermostat bypass hose and find the most efficient route out of the generator cocoon and on to the water heater and back. Thanks for the input and I will update on progress.

[bclaude]

The Onan keel cooler option does away with the raw water pump and heat exchanger so that's not an option unfortunately.

[bclaude]

Originally Posted by Locquatious

We looked into that with our Northern Lights generator, which probably has the same block engine. That is, when you look up parts for the NL, matching Perkins and Kubota parts show up.
Northern Lights and the local NL service manager did not recommend it. They say that generators should run hard and hot to avoid carbon build-up especially in the exhaust. They recommended keeping the generator at full load, using the electric water heater to add load as the battery load drops. They recommended running air conditioning to add load, even if you don't want the cool, toward the end of the battery charging cycle.
Besides, they said it would void the warranty.

Your points are well taken and should be factored in. My wife's input is: If it ain't broken, why fix it" but at the same time she is the biggest complaint when we have cold showers... Apparently these genset rarely fail because of over load, usually it is the other way around as confirmed by your dealer. My Onan is 3 years old and out of warranty and the manual does advise to run the genset in the 25 to 75% range. The setup will not slow down the genset warm up phase as no heat will go to the calorifier as long as the Kubota thermostat is closed. I do have a large battery bank and therefore the chargers and water maker alone do keep it well well into the prescribed range. I need to mull this over.

[Valmika]

Why not run both electrical and coolant heating elements? Seems like you would get hot water even faster then once its hot shut down the electric element and have the genset charging everything else.

[bclaude]

Originally Posted by Locquatious

We looked into that with our Northern Lights generator, which probably has the same block engine. That is, when you look up parts for the NL, matching Perkins and Kubota parts show up.
Northern Lights and the local NL service manager did not recommend it. They say that generators should run hard and hot to avoid carbon build-up especially in the exhaust. They recommended keeping the generator at full load, using the electric water heater to add load as the battery load drops. They recommended running air conditioning to add load, even if you don't want the cool, toward the end of the battery charging cycle.
Besides, they said it would void the warranty.

Originally Posted by Valmika

Why not run both electrical and coolant heating elements? Seems like you would get hot water even faster then once its hot shut down the electric element and have the genset charging everything else.

Exactly my point.

[bclaude]

Originally Posted by Sailmonkey

The engine sounds like a kubota 1105. If that’s the case, the water heater is typically attached to the thermostat bypass hose. No weird plumbing required. The only concern I would have is the 5-6M round trip

Dumb question Sailmonkey, I suppose that the thermostat is normally closed and therefore the thermostat bypass hose is the coolant hose right ahead of the heat exchanger. That is where I was going to connect my loop. Are you suggesting something different?

[Pete7]

Originally Posted by moseriw

maybe practical but tricky as usually the engine is connected to the boiler. In this case you mix engine coolant with genset coolant.
Safe and easier way: use another boiler if you have room enough.

If you read his post, he says he has a twin coil calorifier tank. So he has a spare unused coil inside the tank that could be used by plumbing in the generator heating system, just as you would with a small yacht engine. If you are not familiar with a twin coil calorifier, then here is a link:

https://www.surejust.co.uk/22-litre-...cal-calorifier

Since its very common to connect the engine cooling system to a calorifier, what is the problem connecting an generator. Is there a higher risk of contamination of the water tank? why is one system safe but the other not?

Now that said, the one concern I would have is if the generator is only run for short periods which won't heat the water to a safe temperature. Instead leaves the water lute warm and therefore the risk of something growing in the tank. This could be compounded by more frequent short periods of charging.

Pete

[Flatswing]

Originally Posted by Manateeman

Well I can think of one reason not to do this...the potential for a leak in the coil inside your water heater. Doesn’t take a lot of antifreeze to kill somebody. Nasty chemical in the body even at sub lethal levels.
If you run pure water in both engines you would not have a problem with the toxicity of antifreeze but I’m not sure how happy the engines would be.
I have no idea if you can run diesels on non toxic antifreeze.
An antifreeze leak into the water you wash your dishes with would be very difficult to detect. In a shower, you breathe in mist and the air in your lungs might contain very fine droplets of antifreeze. I’m not sure there are even any studies on the toxicity of anti corrosive boiler additives. I’ve been thinking about adding them into my hydronic system which runs on distilled water as it flows through a coil in my hot water tank. Just haven’t had time to research this. The coil and the tank are 316 stainless but pin holes could push antifreeze through a coil or plate heat exchanger. Once antifreeze starts to accumulate in your tissues, it does some interesting damage. Your lungs are more delicate than you think. People exchange something like 10% of their lung volume while manatees exchange 90 % in a breath. Let’s them sleep on the bottom for 15 minutes at a time. They have great lungs...just bad breath.
I’ll do some more research on anti corrosive additives but I’m a bit concerned about the toxicity issue of antifreeze in this configuration.
Happy trails to you.
Captain Mark and his “Forensic File” watching manatees.

While I accept the above in theory, probability is very low, which is why so many boats heat hot water with their primary coolant in addition to an electrical element when moored. As I understand it, typically engine coolant pressures are lower (my coolant cap I believe is 7-8PSI) whereas pressurized water is usually in the 30-40psi range. Result: pin hole leaks tend to show up as increasing levels in the coolant overflow tank rather than bad tasting hot water (assuming you like to drink your water hot).

[GoneDiving]

How much of the genset coolant will be diverted to the calorifier? When the HWS is at near final temp you will be heating the house water but will you still have enough hear transfer elsewhere to cool the generator coolant and not overheat the genset?

[Manateeman]

The FDA will not permit you to use ethylene glycol in any coil or plate heat exchanger. You never see it in food processing plants. Your lungs “drink” hot water when you are in the shower.
It’s very, very difficult to detect in process water but it accumulates in your tissues so even tiny levels build up over time.
I know, it is used in some boats but why take a chance with such a toxic chemical. Why do you think it’s prohibited in food processing? I don’t think anyone looks at issues like this in yachts so there is no data.
No data does not equal no cases.
You get sick and do you think anyone would connect the hot water system on your yacht with your illness? Remember Legionnaires Disease? It was a long time before anyone looked up on the roof and did a test.
Ethylene glycol is a great way to kill someone painfully. I’m not going to get into the pressure / pinhole discussion in which I don’t concur with you. Let the owner decide what risk he is willing to take. My post was intended to provide additional facts and not simply opinions. It’s a toxin. The FDA is aware of the danger in a heat exchanger application. It can accumulate in your body and you and your Doctor might not discover that the source of your illness is on your yacht.
High downside risk, not much benefit. But...
Happy trails to you.
Mark and his “please don’t pee into our drinking water sea” manatees

[mako]

Ideally would be to have a twin coil calorifier but with double wall heat exchange loops. That’s for safety of course. And relocate the water heater closer to both sources, right next to them.