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Old 02-08-2020, 01:35 PM   #21
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I have an earlier version of the ITR cabin fan catalog, and it specifies the same heat output at 110 deg F. Typo? I don't know. 170 would certainly be more reasonable, as the cycling thermostat in the ITR is set to go on at 160 and off at 180.

What I can tell you for certain is the Suremarine specs are for the component alone, not the assembly. That is, the heat exchanger as a component is rated by the manufacturer under lab conditions to do what the graphs say. This is what Suremarine told me directly. Similarly, the fan is rated by the manufacturer for that CFM standing alone. You can look that up from the part number.

Fans are the particular weak point of the Suremarine: they use small brushless axial fans to keep the noise down. This also keeps the heat output down. Axial fans with short shrouds - 20 or 25mm in this case - are very intolerant of any pressure rise, so anything blocking the output - like a heat exchanger or any ducting - reduces the CFM very substantially. Longer shrouds like 50 mm mitigate that to some degree. You can find this in many manufacturer's specs. Of course a radial fan is much more tolerate of back pressure.

The ITR exchangers have much larger fans, with longer shrouds. The air output is considerably higher as an assembly and the difference is not at all subtle. In fact I have purchased 50mm thick, higher cfm fans to replace the Suremarine ones which I will install this spring. CFM in fans is pretty much related to power. I do not know how ITR specs the cfm (fan alone or assmbly?) but I can tell you without doubt the output is much higher.

Similarly the heat output of the exchanger assembly is much higher. On the sailboat I have 3 Suremarine and 2 ITR heat exchangers on the Hurricane II system, on the same loop. The difference in heat output is dramatic. On the trawler, I have 1 Suremarine and 2 ITR on the Zephyr system, again the heat output difference is dramatic. You are welcome to drop by and experience it for yourself. Nothing against Suremarine, I like the people and the company - but don't believe those specs. The fans need to be much larger to achieve that output. The 5kbtu rated air handlers on the sailboat are each blowing through about 2' of duct with one 90 deg bend. I'd estimate the heat output is less than 2kbtu, based on the fact that a 500W electric heater will heat that cabin quicker (they are in the heads and guest stateroom). The ITR exchangers seem to achieve their rated output, guessing from electric heating equivalent.

On power, the Zephyr is spec'd to run at 6.5A. The March circ pump is about 2.5A, and the fans about 1.5A all running. That'd be 10.5A full on, though in practice I measure it at about 9A. For 20 seconds or so during starup, another 5A or so for the igniter. So I'll say 117W. On the Hurricane II, it seems to be about 10 or 11A running. Those are measurements, not specs.
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Old 02-08-2020, 02:04 PM   #22
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I have an earlier version of the ITR cabin fan catalog, and it specifies the same heat output at 110 deg F. Typo? I don't know. 170 would certainly be more reasonable, as the cycling thermostat in the ITR is set to go on at 160 and off at 180.

What I can tell you for certain is the Suremarine specs are for the component alone, not the assembly. That is, the heat exchanger as a component is rated by the manufacturer under lab conditions to do what the graphs say. This is what Suremarine told me directly. Similarly, the fan is rated by the manufacturer for that CFM standing alone. You can look that up from the part number.

Fans are the particular weak point of the Suremarine: they use small brushless axial fans to keep the noise down. This also keeps the heat output down. Axial fans with short shrouds - 20 or 25mm in this case - are very intolerant of any pressure rise, so anything blocking the output - like a heat exchanger or any ducting - reduces the CFM very substantially. Longer shrouds like 50 mm mitigate that to some degree. You can find this in many manufacturer's specs. Of course a radial fan is much more tolerate of back pressure.

The ITR exchangers have much larger fans, with longer shrouds. The air output is considerably higher as an assembly and the difference is not at all subtle. In fact I have purchased 50mm thick, higher cfm fans to replace the Suremarine ones which I will install this spring. CFM in fans is pretty much related to power. I do not know how ITR specs the cfm (fan alone or assmbly?) but I can tell you without doubt the output is much higher.

Similarly the heat output of the exchanger assembly is much higher. On the sailboat I have 3 Suremarine and 2 ITR heat exchangers on the Hurricane II system, on the same loop. The difference in heat output is dramatic. On the trawler, I have 1 Suremarine and 2 ITR on the Zephyr system, again the heat output difference is dramatic. You are welcome to drop by and experience it for yourself. Nothing against Suremarine, I like the people and the company - but don't believe those specs. The fans need to be much larger to achieve that output. The 5kbtu rated air handlers on the sailboat are each blowing through about 2' of duct with one 90 deg bend. I'd estimate the heat output is less than 2kbtu, based on the fact that a 500W electric heater will heat that cabin quicker (they are in the heads and guest stateroom). The ITR exchangers seem to achieve their rated output, guessing from electric heating equivalent.

On power, the Zephyr is spec'd to run at 6.5A. The March circ pump is about 2.5A, and the fans about 1.5A all running. That'd be 10.5A full on, though in practice I measure it at about 9A. For 20 seconds or so during starup, another 5A or so for the igniter. So I'll say 117W. On the Hurricane II, it seems to be about 10 or 11A running. Those are measurements, not specs.

Thanks. That's all very helpful. I'm in the middle of building a new system, so particularly interested.


Those March pumps are miserly indeed. I had a Grundfoss moving significantly more water, and using correspondingly more power.


Fingers crossed my new system works well. The last one did, so I'm optimistic.
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Old 02-08-2020, 03:04 PM   #23
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You've got a big boat there, my sailboat is 45' and the trawler 34'. Also you have a lot more power to play with. In that situation I'd probably use the Kabola. For heat exchangers, if you are going through much ductwork I'd use the radial fans. A lot more power and more noise, but they will push air through ducts and the axials will not. I think ideally I'd use Suremarine exchangers, but modify or replace the fan plate with one holding a large diameter fan (the ITR high output are 6"). You can tune the CFM by fan selection, they aren't expensive to experiment with. On the ITR system, there is the option for two speed fans, accomplished by simply putting a dropping resistor in the line. Because they are brushless DC, the power will be reduced too (though not as much as the output) but the noise goes down as well. For fast heat up, put it on high, normally leave it on low.

The reason I'd do that using the Suremarine instead of the ITR, is that the Suremarine have threaded water connections which allows you to use PEX hose fittings and plumb with PEX. That would be a better installation than hose, which is sometimes problematic to keep tight.
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Old 02-08-2020, 03:41 PM   #24
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FWIW, Sure Marine will work with you in getting the heat exchangers you need. Many of their units are available in multiple configurations with different fan options to balance output, noise, and power consumption. I have worked with them on multiple installations of Olympia units, Webasto units, and providing supplemental parts for Hurricane units. It is also easy enough to source AC fans for their heat exchangers to make an Olympia installation entirely AC powered.
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Old 02-08-2020, 04:05 PM   #25
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Suremarine is great to work with. That said, when I ordered this last heat exchanger, I asked for the largest fans they had, and it is still woefully inadequate. They only work with the parts they stock. It is relatively easy to modify or make a fan plate to take your own sourced fan though. A place like Digikey lists 10s of thousands or choices.
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Old 02-08-2020, 05:32 PM   #26
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Iíll look at largest fans if some zones are too cool. I have been expecting to reduce the fan capacity in a few spots like heads which are easily over heated.

All plumbing is PEX except for the big 1-1/2Ē loop through the boiler and manifolds.
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Old 02-08-2020, 07:02 PM   #27
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Newark also.
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Old 02-08-2020, 07:25 PM   #28
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Iíll look at largest fans if some zones are too cool. I have been expecting to reduce the fan capacity in a few spots like heads which are easily over heated.
Wouldn't the heads have their own thermostat?

Here is an example of the axial fan problem. From the Mechatronics catalog, the brand and size that Suremarine uses (though others are similar). Note the precipitous drop in CFM with even slight backpressure: 60% or more lost at only 0.05" H20 (about 0.002 psi).

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Old 02-14-2020, 09:20 PM   #29
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We were full time on board several winters with an ITR Hurricane 28,000 btu Hydronic heater with 3 zones. With the system boiler firing I only saw a max amp draw of 32 amps 12 volts DC. Without the boiler firing(ie using engine heat with just the circulator (12 volt march) pump and the zone muffin fans it drew less that 6 amp 12 volts dc/. When we sold the boat The system had 1990+ hours on the hobbs meter without a single failure or any maintenance done on the system of any component. We loved it. It was less than dock power kw costs per btu and the water was too cold < 40 degrees to use reverse AC for heat. I loved how easily accessed the components were which were all easy to just R&R. All in all a robust simple heater except for the control board printed circuited board which is an R&R as well.
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Old 02-14-2020, 09:58 PM   #30
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The boiler alone only draws about 6A, except for a few seconds when the igniter is lit. If you saw 32A, something else was using it. I run my whole Hurricane II hydronic system on a 20A dc-dc down converter, and it is lightly loaded most of the time and has never blown the 20A output fuse.
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Old 02-15-2020, 12:21 AM   #31
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I would think reliable heaters should have minimal repair issues that are logging around 1000 hrs a year.


At 500 hours a year...it is almost underused to stay reliable.


My Wallas has required about 1 hr cleaning per year and a couple inexpensive parts over a 7 year period and now has a little over 3700 hours on it.


I would hope the ITR with its reputation would be just as reliable.
I just took one of my Wallace heaters out of service and replaced it with the new viking unit.

The old furnace had over 27,000 hours on it.

I’ll be replacing another one this year with similar hours.

What a GREAT service life. Yes like anything they need their maintenance, but to get that kind of life out of something is Amazing!
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