Ron, literally thousands of us have this installation. Not an issue, but a reasonable possibility from pure forensics.
How long to heat water
- Thread starter Hayden Watson
- Start date
That's too bad, Hayden. I feel your pain. A decent water heater is not super-expensive, assuming you can install it yourself, but then, it's not in everyone's budget, and there are usually priorities. I see a Seward 6 gallon unit at $254, free shipping.
The case on my original Seward 6 gallon rusted badly and then the tank developed a leak. I was hoping that the Kuuma would hold up better because it has a stainless steel case and uses the same heat exchanger design. There are several other boats on my dock with the same Kuuma that heat up very fast so it is a personal problem. {sigh}
You say you expect nearly 100 % efficiency of heat transfer in the water heater, but if you were getting that, then the temp at the outlet of the water heater's heat exchanger would be the same as the heated water temperature. Sounds to me like you have a faulty heat exchanger loop in the water heater. Perhaps not enough contact between the inner & outer tubes.
What I said was that the transfer is nearly 100% efficient not that the exchanger was 100% efficient. In measuring the transfer you have BTU's / minute and what ever you take out of the coolant you will put almost 100% of those BTU's into the water. My problem is that I am just not able to get many BTU's out of the heat exchanger even though there is a significant temperature difference so I fully agree that I have a faulty exchanger. The only thing that makes any since is that when they bent to U shape into the tube-within-a-tube pair they stayed concentric with very little contact.
Hayden, Have you contacted KUUMA and asked about the heat exchanger? Do they have a fluid between the outer and inner tubes. If not then the air gap would act as an insulator and I can see how your problem would occur where your friends units work more to the design you expect.
Not necessarily. I have a 6 gallon Kuuma that came with the boat. Same problem you have been having. Slow to heat water with motor. Replaced it a couple of months ago with the same hoping for an improvement. I have not seen a big improvement. You are not the only one.
jssailem, Kuuma engineering tells me that the exchanger is just a tube in a tube with an air-gap between. They feel that the process of bending puts enough of the two pipes into contact to transfer the heat by metal to metal contact while maintaining the safety feature of external draining of any leaks.
nautikaljeeper, you are the first to say that they have had less then great heating like mine. I assume that you have tried all of the things suggested to me in this thread. Burp, purge, thermostat, IR thermometer to check inlet/outlet temp...
nautikaljeeper, you are the first to say that they have had less then great heating like mine. I assume that you have tried all of the things suggested to me in this thread. Burp, purge, thermostat, IR thermometer to check inlet/outlet temp...
Apparently what Kuuma engineering “feels” is not what is experienced in the real world.
Seems like there should be an engineered heat transfer connection between the two tubes. Not just rely on incidental contact during the manufacturing process.
The only size that will fit into the available space is the 13"x13" standard 6 gallon cube. It looks like this size is made by Kuuma, Seaward and Attwood. The Kuuma and Seaward both appear to have the same "U" double tube exchanger but the Attwood looks like it might have a 1½ loop coil because the inlet is at a different elevation than the outlet.
I have this same issue with my 11 gallon seaward... just doesn’t heat up quickly. So this coming weekend I am changing fresh water coolant and all hoses. Here is a question (maybe dumb)..... is there a specific way to hook the hoses up? I mean does engine hose “a” have to be attached to water heater inlet “a” to have it flow In a certain direction?
The heat exchanger in a horizontal loop water heater is not directional the inlet is the end that receives water from the engine and the outlet returns it. If the exchanger loop is vertical there might be some gain to one orientation over the other but I do not think it would be very large. In a vertical coil exchanger you would typically have the inlet at the bottom to supply the hottest fluid as low a possible.
That is a nice unit and with a 10' long exchanger it should certainly heat quickly. Cost of over double of the other three so I might need to do some talking to get that!
That is where I checked and with my Oak Harbor discount the BXS is $660, Seaward SS is $330 and Kuuma is $240.
does your h w h have a mixing valve at outlet that may be frozen shut in the maximum cold water add position ? many boat h w h s have this mix valve on the outlet. an owner who does not adjust it will have cold water mixing with hot as it comes out of the tank , making an unpleasant lukewarm water mix at the taps. if the mix feature is malfunctioning, as soon as the hot comes out of your tank, an equal amount of cold mixes with it . thus you get 80 degree water not 115 in your taps...
Hayden, I got a Seaward at Sure Marine for $260 + s/h in 2013. You can do better. Google internet shop. I don't think they sell them here, but try, too.