Two tankless water heaters?

[bigskypc50]

Greetings everyone I have very cold ground water and very low pressure where I live. I have not had good luck with tankless water heaters in the past, so I am wondering if I bought two of the Excel tankless ventless water heaters and fed the output of the first unit into the second one if I could get good nice hot water out of that at the max 1.6GPM flow they are rated for?

[Tango]

You might check with "Ol' Trunt" (aka; Jack). As I recall, he discovered that you can over pressure the system if you are not careful and blow stuff up with too much heat/steam pressure. But...(also as I "recall") I think he figured out a fix.

[milkmania]

Originally Posted by bigskypc50

Greetings everyone I have very cold ground water and very low pressure where I live. I have not had good luck with tankless water heaters in the past, so I am wondering if I bought two of the Excel tankless ventless water heaters and fed the output of the first unit into the second one if I could get good nice hot water out of that at the max 1.6GPM flow they are rated for?

personally, I've got great pressure... But, being the inquisitive one, I've experimented with my eccotemp L5.

I've got a portable hottub, and had a harbor freight transfer pump 12volt laying around... I plumbed to pick up water from the tub, feed through the heater, and back out to the tub... worked awesome! now, I did not run it back through a shower head to see if I'd like the pressure... but, what I saw on the outlet hose was similar to my regular water supply pressure.

Bryan at Eccotemp showed me how to adjust the propane burner and water pressure inlet to a range outside of factory specs, with 2 adjustment screws... so, that along with a standard garden hose ball valve... I can hit 192 degree outlet temps!

I know it doesn't answer your original question... but it might give you an idea what your heater is capable of.
personally, I think hitting the second heater with hot water isn't going to help you much. there might even be a high limit switch incorporated in your heater.

HF pump $39.99... wait for a sale!
https://www.harborfreight.com/12-vol...ump-63324.html

garden hose ball valve
https://www.amazon.com/Gilmour-Conne.../dp/B0006U66B6

also created a PEX manifold with Shark Bite ball valves and fittings to go to the shower and clothes washer... has worked great for over 2 years
Shark Bite fittings are awesome, because they're reusable!

[ol trunt]

Forget the second water heater. Remember, the Ecotemp heats ambient temp water by a set amount (can't remember the specifics). Therefore the hotter the water going in the hotter the water coming out. I put a recirculating circuit on my ecotemp to assure me of hot water nearly instantly. The problem was that as input ambient rose in temp so did output--until my hot water lines grew soft and finally gave up!?! I solved my problem by installing a thermocouple on the outlet that shut down the ecotemp at the temp I wanted. That works great. You migh consider a dedicated hot water tank coupled with a thermostat and a recirculating valve. I use a dedicated water pump one for hot and one for cold. This arrangement provides me with flawlessly regulated hot water temps and has done so for a couple of years.
Jack

[ThunderstruckStudios]

Bigsky,


Be careful of overheating the water. Even if the bulk of it doesn't boil (reach 212 F), there's a phenomenon called critical heat flux - basically a really thin layer of water next to the hot outer wall of the pipe (that's being heated by propane) can boil locally, creating a vapor gap, which then insulates the water in the center of the pipe. The temperatures inside the pipe can jump up super rapidly, ultimately causing the pipe to fail from excessive temperature of excessive steam pressure.


Short version: rapid overheating = pipe bomb. Not recommended.

[Njsurf73]

What about a small (20 gallon) holding tank with a water pump. Would solve the low pressure issue and should allow the water to at least come up to ambient temperature and you don't have the worry of overpressure.

Originally Posted by bigskypc50

Greetings everyone I have very cold ground water and very low pressure where I live. I have not had good luck with tankless water heaters in the past, so I am wondering if I bought two of the Excel tankless ventless water heaters and fed the output of the first unit into the second one if I could get good nice hot water out of that at the max 1.6GPM flow they are rated for?

[Rivetboy]

Originally Posted by ol trunt

Forget the second water heater. Remember, the Ecotemp heats ambient temp water by a set amount (can't remember the specifics). Therefore the hotter the water going in the hotter the water coming out. I put a recirculating circuit on my ecotemp to assure me of hot water nearly instantly. The problem was that as input ambient rose in temp so did output--until my hot water lines grew soft and finally gave up!?! I solved my problem by installing a thermocouple on the outlet that shut down the ecotemp at the temp I wanted. That works great. You migh consider a dedicated hot water tank coupled with a thermostat and a recirculating valve. I use a dedicated water pump one for hot and one for cold. This arrangement provides me with flawlessly regulated hot water temps and has done so for a couple of years.
Jack

Good Morning Jack,

So my undestanding is you have an auxillary water tank with a pump connected to the output side of the water heater . The water heater and the pump to recirculate hot water through the tank are on a thermostat.
Do I need more coffee?
Is the recirculating valve supposed to read "pump"

Joe

[bigskypc50]

Wrote the manufacturer. They said it should not be a problem with that setup.

Hello Eric,

Yes you can connect them in series to achieve a higher delta in temp increase for 1.6gpm.

You can tinker with the gas knob and the water flow knob for the desired performance

You can buy them at this link:

http://excelonlinestore.com/excel-16...p-ventfree-lpg

Excelamerica , LLC
Fernan Ech Usher
6010 NW 99 Ave
Unit 107
Doral, FL 33178
USA

gasflex is a registered trademark USPTO

[ol trunt]

More coffee----

2 pumps, 1 hot, 1 cold both from same tank.

water heater output goes to both the faucets and to a solenoid valve which diverts hot water back to main tank. Water can flow through either or both. As long as there is water flow and pressure, the heater will stay lit rather than constantly cycling. This assures hot water "instantly".

These heaters maintain a temp differential based on the ambient temp of the inlet water. As the main tank drew down, its ambient temp went up due to the recirculation of hot water --all the way up to 150 degrees F. That was hot enough to melt the joints on my PVC water pipes and make a mess. With a thermocouple switch on the heater output side I am able to control the upper temp limit within a couple of degrees without nearly as much heater cycling.

If you are stuck with very cold inlet water, a 2 tank system (1 hot, 1 cold) would hasten getting your inert water temp to within the desired heater temp differential. Ha! Clear as mud.
Jack

[dan-fox]

Originally Posted by ol trunt

These heaters maintain a temp differential based on the ambient temp of the inlet water. As the main tank drew down, its ambient temp went up due to the recirculation of hot water --all the way up to 150 degrees F. That was hot enough to melt the joints on my PVC water pipes and make a mess. With a thermocouple switch on the heater output side I am able to control the upper temp limit within a couple of degrees without nearly as much heater cycling.Jack

Do I misunderstand your setup, or are you at risk of having 100 degree water coming out of the cold faucet? Not conducive to a good shower if both faucets are the hot faucet.