Tankless with Recirculation Loop for Trough Heat

[UtahYoutubeGuy]

When I took over my old zombie wash 3 years ago I was surprised that the existing 100 gallon commercial water heater still worked and wasnt rusted out. So I have used it for 3 years and it finally sprung a leak. I tossed the water heater and temporarily bypassed everything to run cold water for now.

Now I am in the preliminary stages of researching putting in a tankless. Just so everyone knows here is my setup. 4 SS bays off a Carolina Pride stand with the hot presoak running a recirculation loop in the trough. I am in the permitting process of building a small building for a dog wash on the end of my bays that I will install an IClean dog wash in that I have already purchased and is in storage currently. The Iclean dog wash by the way has a small on board tank water heater that I want to eliminate and not deal with.

This is what I want to do. Install a Navien 199K with onboard recirculation and run a recirculation loop to the dog wash and all the way through my trough to eliminate the hot presoak recirculation loop I currently have. The presoak recirculation loop on the Carolina Pride stand is the one design I dont like because that pump has to run 24/7 365 rain or shine. I would convert to something simpler like a flojet for the presoak. I would plumb this new recirc loop to have a bypass so that in the summer when I dont need to heat the trough I can just go to the dog wash only and back. The length of the loop in the winter would be about 220' and in the summer it would only be about 95'. As a recap the fixtures needing hot water are the gravity tank feeding the 4 cat pumps (Soap, Rinse, Wax) and the hydrominder filling the presoak tank, then I have a small kitchen sink, and then the future dog wash.

What flaws do you see in this system and what words of advice do you have for setting this up?

 

[OurTown]

The flow is very low from the tankless units. You should look at the manual of the tankless unit you are looking at to see that chart. If you don't want to compromise on the temperature at the bays and don't want a storage tank/circulation pump then you will probably need three 199K units. If you are willing to compromise on temp at the bays then you could put in a cold water float valve on the gravity tank set a little bit lower than the hot water float valve. That's what I did but we have less need for hot water because it's just a three bay and bath sink. The 199K unit can't provide enough for even two of our bays.

 

[Earl Weiss]

I replaced the trough loop with heat cable connected to output 2 of the weepmizer. (Needs a relay) Only runs when weep mizer tells it to plus it has a built in thermostat. Much simpler and I think it worked better.

 

[TMoliver]

I agree with Our Town that most instant heaters are low volume 2.5-4 gpm as they were designed for home use not commercial. However there are a new commercial line that are 8-10 gpm. One brand to look at is AO Smith. They can even be linked together for higher volums and alternate between units based on usage. Controls are built in .

Let us all know which way you ended up.

 

[OurTown]

I agree with Our Town that most instant heaters are low volume 2.5-4 gpm as they were designed for home use not commercial. However there are a new commercial line that are 8-10 gpm.

We have a Takagi rated at 10 GPM but states 9.5 @ 40F rise. If you run it at say 110F then your incoming water needs to be 70F plus to get the rated flow.

 

[OurTown]

@2Biz

 

[AnalyticWash]

What flaws do you see in this system and what words of advice do you have for setting this up?

I would not use water only on a trough heat system. If you loose power or the heater goes out the freezing issues will be a nightmare. RV antifreeze is the generally accepted solution...

I would just use the on board heater on the dog wash unit. It will not run out unless you are very, very busy. Unlikely on a self serve only dog wash site.

Have you finalized your dog wash room design yet? PM me if you want some tips.

 

[Car_Wash_Guy]

I replaced the trough loop with heat cable connected to output 2 of the weepmizer. (Needs a relay) Only runs when weep mizer tells it to plus it has a built in thermostat. Much simpler and I think it worked better.

I turned off the loop in my trough and put a heat cable in myself. I believe it's a self regulating one which seems to be working great.

I found that to keep that trough from freezing. I had to keep my floor heat higher than I needed to to keep the temperature in the trough high enough.

 

[Randy]

Install a self regulating heat tape in your trough and control it with your Dixmor Weepmizer output 2 with a relay on it. This will save on your gas and power bill.

 

[2Biz]

We have a Takagi rated at 10 GPM but states 9.5 @ 40F rise. If you run it at say 110F then your incoming water needs to be 70F plus to get the rated flow.

My Takagi T-H3-DV-N is rated for 10gpm....Like you state, thats with only a 40° rise. One thing you left out of the equation is inlet pressure. The manual states it needs at least 40psi inlet pressure to get maximum flow rates (debatable). I have 40psi feeding mine and I get 6.6gpm at 105° set point and inlet temps between 55°-70°. Fluid temps out to the bays/trough about 90°. So not quite the advertised flow rates. But at this setting, it keeps my 4 bay floors from freezing down to a tested minus 16° with capacity left. So it works and I'm not complaining!....

I also have one loop running through the attic, but also have a self regulating heat cable running in the loop too. It Allows flexibility. I have both the floor heat and heat cable turn on at 32° off output 2 on the weepmiser (using a 30a relay), but can control both (on-off) with simple light switches. There are times when temps dip to 25° and I don't need floor heat if the daytime temps are above 40°. So I manually turn off the floor heat and just let the heat cable turn on. It alone keeps my (insulated) trough at 110°. When the floor heat is on, its just a bonus....Once temps stay below freezing, I let the complete system run by itself....

A word of advice, You have to learn how to read the flow charts in the manual for whatever brand heater you chose to make sure it works the way you Think it should work. Do your calculations and estimate head pressure to calculate flow rates and compare to the flow charts....In a primary-secondary system, on the heater loop, you won't have head pressure to calculate on flows since the pump/pumps are close to the heater. I have (2) taco 013's in series to produce 40psi to get 6.6gpm flow through the heater. A single 013 produces 3.3gpm! Hmmmm... Ask me how I know!

 

[AnalyticWash]

Install a self regulating heat tape in your trough and control it with your Dixmor Weepmizer output 2 with a relay on it. This will save on your gas and power bill.

With a high efficiency boiler I would doubt heat tape is a cheaper option. 140' heat cord draws 1200ish/watts @ 32 degrees. Plus it takes time to build heat which makes it impractical to run off a Weepmizer imo.

My personal experience is heat tape only works if you are in an area that doesn't see extreme temp change. If you have sub freezing temps for days at a time I would not consider it a great solution. In a pinch maybe.

 

[Earl Weiss]

With a high efficiency boiler I would doubt heat tape is a cheaper option. 140' heat cord draws 1200ish/watts @ 32 degrees. Plus it takes time to build heat which makes it impractical to run off a Weepmizer imo.

My personal experience is heat tape only works if you are in an area that doesn't see extreme temp change. If you have sub freezing temps for days at a time I would not consider it a great solution. In a pinch maybe.

My heat tape in an insulated trough on the roof. works great to -15 degrees with people washing in the single digits. (Actual temps - not wind chill) (Chicago North Suburb) Since you run the heat tape of output 2 it stays on once the set point is reached and stays below that point so building heat is not an issue. I used the heat tape to replace a separate heated glycol loop.

 

[soapy]

I have been using Heat tape instead of the trough loop for 30 years. Never had to replace one heat tape and had constant battle with pumps etc. when doing the loop thing. Raytheon winter guard wet is what I use. It has a extra layer of protection. Self regulating also.

 

[2Biz]

Same here on the winter guard wet in an insullated trough....I've had it installed for over 10 years and miraculously all my freezeups went away! The trough loop was already there, so I left it hooked up. It doesn't really steal from the slab since there is very little heat loss on that loop.

 

[OurTown]

Do you guys wrap the heat tape around your hoses, zig-zag underneath them, or run it straight down the middle? Do you use just one wire or multiple?

 

[2Biz]

I just laid mine on top of all the hoses. My hoses are in a 5-6" thin wall PVC pipe. The previous owners just had holes cut in the pipe where the hoses entered and exited! What a pain that was to pull any new hoses. So I cut a 2" wide slot in the top of the trough to make it easy to work on. After putting in the heat tape, I filled the PVC pipe with strips of pink insullation so there is no air gap in the pipe which I think is important.... I also installed (2) temperature probes and monitors on both sides of the ER so I can see what temp the trough is to make sure the heat tape is working. I just use (1) wire) and keeps trough at 110°.

 

[Earl Weiss]

Do you guys wrap the heat tape around your hoses, zig-zag underneath them, or run it straight down the middle? Do you use just one wire or multiple?

MY roof trough is metal about one foot wide and 10 Inches high 1" rigid foam insulation on bottom and sides. And top. Heat cable just lain in trough