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2Biz

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Glad you guys are finally figuring out what I've been preaching for years! If you are running close on hot water supply on busy days, lower the setpoint by 10° and you might gain enough capacity to get you through the day. For my floor heat, the Takagi 199K Btu I have is rated for 10gpm...That's AT Maximum Operating Conditions. This is at the highest inlet pressure and minimum setpoint temp! @ 105° setpoint and 40psi inlet pressure, I get 6.7 gpm flow. Luckily it is enough to keep my slabs ice free. I would have to have lots of wiggle room if I were to trust one to feed my HP pumps! Too risky for me....

I also have mentioned in a lot of threads, most of these heaters have tiny inlet filter screens...You might want to have a few spares since they get blocked very easily. The things that happen on busy days! The heat exchangers in these heaters have very tiny orifices to get the amount of heat transfer they need. Hence the filter screen. Pesky little hidden time bombs!
 

bert79

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2Biz, how often do you check the filter screens on your unit? Are they fairly easy to access? I should mention just for the sake of clarity that our ss pumps are fed from gravity mixing tanks (I'm sure a lot of folks have the same set up). So the hot water is sitting in the tank ready to be used when called for by the pumpps. This probably helps us with supply issues since not everyone is using a hp hot water function at the same time (the tank has time to fill back up with hot water). Also the low pressure pump on the lw4000 pump stand is direct fed with hot water from the tankless units.
 

2Biz

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The screen filter on my Takagi goes in the cold inlet at an angle just at the base of the heater. Kind of like a "Y" Strainer. There is a cap that unscrews and the filter comes out with it. When I installed the Takagi for my floor heat, it plugged up right away. So I installed a 5 micron pre-filter in the system for several days to give the system a good cleaning. Evidently that took care of it because I haven't had any trouble since. It never varies from 6.7 gpm. If it did, I'd know right away what was wrong.

But it is a closed loop pressurized system where nothing can get in. Its not uncommon to see sand in the bottom of my float tanks from the city water supply. Looking at the filter in the Takagi, it looks like 100-120 mesh and is only about as big around as a dime.

I don't know how big your gravity float tanks are, mine holds about 10-12 gallons. If the tanks are starving for water, that will last about a minute if all 4 bays are using soap or wax....So not much backup volume!

If your heater has a filter similar to mine, I'd be checking it every month till I got comfortable with extending the cleaning cycles. But as you can see with my filter, it wouldn't take much to plug it. Its pretty small!

 

MEP001

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Off-topic from this thread, 2Biz, but I noticed your Facebook address is the default one created with your page. You can edit it at least once to make it simpler to get to.

www.facebook.com/MastersonWash
 

Earl Weiss

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I checked my Navien yesterday set at 120 degrees. The readout can tell you all sorts of stuff if you push the correct buttons. Output was 5 GPM.
 

2Biz

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My Takagi displays Input temp, output temp, and GPM....

Is 5 gpm enough to run your HP pumps? I would need 3 Naviens to run my 4 bay at 5 gpm output each….
 

kentadel

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I have 2 Rheem 199 btu's for a 2 & 1 and have no problems supplying the pumps. Setpoint is 115. Adding a 2nd IBA shortly and will try adding it to them.
 

2Biz

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I've heard some plumb in a cold low water supply to the float tank when using a demand heater if there's ever an issue. There are options...
 

Randy

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I have a 125K BTU gas on demand hot water heater on each bay. My pumps are fed with reduced pressure city water pressure, no hot water supply tanks, no float valves. Very seldom do I have any issues with any of the hot water heaters or Cat 310 pumps, they are over 30 years old.
 

Earl Weiss

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My Takagi displays Input temp, output temp, and GPM....

Is 5 gpm enough to run your HP pumps? I would need 3 Naviens to run my 4 bay at 5 gpm output each….
I do not see the need for 120 Degree water to the SS Tanks / pumps. Just like now I have a mixing valve where i can have cold and or Hot feed the tanks. I adjust the temp so it' warmer in winter. Not as warm in summer. With the added cold water just as it's sufficient to supply a dozen Tunnel mixing tanks at 100+ CPH, it should be sufficient to supply SS Tanks for many bays. Now, if you also have an IBA that could be something quite different.
 

OurTown

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What is the temp out of the guns at the bays for everyone? I'm sure it may vary from bay to bay but has anyone checked it?
 

2Biz

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I run 100° water. Since my trough is heated to 110°, I doubt I loose much from the trough to the gun.
 

wgwagg

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I have 2 Rheem 199 btu's for a 2 & 1 and have no problems supplying the pumps. Setpoint is 115. Adding a 2nd IBA shortly and will try adding it to them.
How are your Rheem 199k btu tankless heaters holding up? I'm looking at purchasing some also.
 
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