Tankless water and radiant heat questions

[Eric H]

I have a 28 year old boiler that is in desperate need of replacement. I have a lot of questions about tankless units. I should probably have 2 posts about this (one for water and one of radiant) but here goes:

This is a 4 bay SS only with an euipment room in the center. I have a similar wash built in 2002 that has 80% eff boilers. Floor heat is 334,000 BTU input, 274,00 BTu output. Hot water is 627,000 BTU input , 524,000 BTU output with a 115 gal storage tank. (this seems over sized)
I have a bid for new boilers from last year that include 399,000 BTU 95% eff boiler for floor heat and 299,000 BTu 95% eff boiler for hot water with a 115 gal storage tank.
So, it looks like I need about:
Floor heat = 299,000 BTU
Hot water = 299,000m BTU
Based on the assumption that the floor heat at the other wash is sized correctly . I never have an icing problem there. And last years bid of 299,000 Btu for the hot water is accurate.
However, all of this is based on BOILERS. I would like to switch to tankless units for everything is possible.
I am hoping that some one can point me in the right direction so I can get moving on this project before the snow arrives.
BTW: the bays would use 15.2 GPM of hot water as currently set up
Thank you in advance. I'm sure there will be LOTS of questions over the next couple of days so I will be monitoring this post closely to answer them a promply as I can
-Eric

 

[Turbo]

Tankless Water Heater

Eric,

I have 3 bay ss and 1 touchless auto. I heat the rinse water for the SS bays and the presoak for the auto.

I have one Eternal tankless Water heater GU195 for 2 years. No issues. Keeps up in all but the busiest days. Even then its good enough. 98% efficient. 199k btu.

If I were you I would buy one and expand if needed. Make sure when you buy one it is expandable to two (not sure if there's a difference but check).

Installed price was $3200 as I recall.

I have not replaced my floor heat yet.

Karl

3 bay Jiffy and 3 ss and 1 auto

 

[Eric H]

Thanks for the reply Karl.

It looks like that unit, and every other one I've seen, falls to a flow rate of about 5gpm at a temp rise of 60 degrees or more.
Coupling 2 or more units together is an option but the increased cost soon surpasses the cost of the boiler combinations I am being quoted.

 

[Turbo]

Tankless

Eric,

A couple more points:

-better use of floor space (my tankless is mounted 8 feet off floor)
-the rinse tank acts as a buffer
-unllikey that you will have all 4 bays needing water at same time FREQUENTLY (once in a while yes); one or more will be using one of the other selections, or be vacant.
-no standby loss
-I just checked google shopping and you can get an eternal gu195s for $1749 plus shipping and install
-on the other hand I am guessing these are more complicated and may break (my raypak floor heat boiler is still working after 20 years). That said there are other posts that have some other NON condensing tankless running for a long time with no issues.
-If I had it to do over again I would install one of these and I THINK if I were you I would do so as well. It seems that you would only have less than ideal temp in a small number of instances annually.
-that's all I have as pitchman for eternal! Good luck.

 

[Eric H]

UPDATE:
We finished up our install last week and all seems to be working perfectly (so far).
I ended up with a HTP Elite EL-399 floor heat boiler. This is 98% eff 399,000 Btu. $6900. This is the latest version of what was once called "Munchkin" boilers.
For the hot water I used 2 Navien tankless units. 99% eff, 199,000 btu each, $1479 each.
Have not received the bill for the install yet.

 

[Mr. Clean]

Eric,

I'm looking at two Navien ch240's to heat water for a six bay. My 30 yr old AO Smith is ready to go. Where did you find these for $1479? Did you do the install or what more did it cost for installation?

Thanks.

MC

 

[Eric H]

I bought the units at my local plumbing supply house (F.W. Webb). I have 2 Np-240 units, but one of them probably should have been a NP-240A. The "A" units have a small circulator pump and a 1 gallon buffer tank internally. Without the circulator i have been getting a "cold water sandwich" because the unit takes a few seconds to turn on when it senses demand. The float valve on my pump stand, a Jobe valve, opens fully and fills the tank too quickly so the tankless is turning on and off too much. My original float valve, A BOB Valve, would open slowly, open up only enough to meet demand and then close slowly. The bob valve or one similar would be better for this application but kept sticking open causing the unit to run all night and fill the EQ room with humidity.
You also need a communication cable from Navien and service valves: http://www.webstonevalves.com/defau...ustomer/wecoin/customerpages/exp_details.html
I could have done the installation myself but had the plumbers do it since they were there for the boiler install anyway. I also needed the plumbers to do it so that I could qualify for rebates, which it turns out are only for the Navien "A" units
Let me know if you have any questions.

 

[mjwalsh]

I bought the units at my local plumbing supply house (F.W. Webb). I have 2 Np-240 units, but one of them probably should have been a NP-240A. The "A" units have a small circulator pump and a 1 gallon buffer tank internally. Without the circulator i have been getting a "cold water sandwich" because the unit takes a few seconds to turn on when it senses demand. The float valve on my pump stand, a Jobe valve, opens fully and fills the tank too quickly so the tankless is turning on and off too much. My original float valve, A BOB Valve, would open slowly, open up only enough to meet demand and then close slowly. The bob valve or one similar would be better for this application but kept sticking open causing the unit to run all night and fill the EQ room with humidity.
You also need a communication cable from Navien and service valves: http://www.webstonevalves.com/defau...ustomer/wecoin/customerpages/exp_details.html
I could have done the installation myself but had the plumbers do it since they were there for the boiler install anyway. I also needed the plumbers to do it so that I could qualify for rebates, which it turns out are only for the Navien "A" units
Let me know if you have any questions.

Eric,

It will be interesting if this turns out to be is a much better solution than a Poloma or other less efficient brands.

http://www.globalindustrial.com/p/p...l-gas-water-heater-circ-pump-mini-buffer-tank

I wonder if the built in circulator solves all flow issues that I have always be leery of with tankless.

MikeW

 

[washnvac]

Just an alternate way to hook the tankless up---I use one single 199,000 btu Rinnai, for a 9 bay s/s. I have a closed loop boiler coil inside a 30 gallon stainless tank, that runs to the Rinnai with a Grundfos circulator.(a fresh water line keeps pressure on the system) The circulator is connected to a t-stat in the 30 gal tank set @ 120. Then I added a multiplexer inline with the t-stat. The multiplexer is hooked to all 9 bays hot signal. No bays fired up, no water heating. As soon as the timer fires; the t-stat is active for heating. Since most folks start with tire cleaner and/or pre-soak, the wash water is hot by the time they hit that cycle--even from total cold. This way also eliminates the worry of how much flow the float needs to deliver to fire the heater, and eliminates short cycling of the heater. I have had it in for 3 years, and it works great with only one heater.

 

[JIMT]

Washnvac.
"I have a closed loop boiler coil inside a 30 gallon stainless tank."
I don't know what this is. I assume you are circulating water from the outlet of the heater and then in to the inlet of the heater. Could you give us a picture and a little more description of the "closed loop boiler coil inside a 30 gallon stainless tank"
Thank you,
JIMT

 

[washnvac]

The Rinnai heats the coil only, which in turn heats the water in the 30 gallon tank. It is similar to the "old" way, in which you had a monster boiler looping to an open tank. But here I am able to maintain 30 gallons of hot water with one Rinnai. The Rinnai flow is only 7.5 gallons per minute max. To direct feed and keep up with 9 bays, I would need 3 or 4 heaters. I found it more cost efficient to have 1 heater and to keep a bit of hot water on standby and not to worry about flow restrictions or heater short cycling.

And you are correct, I am circulating from the hot heater outlet, through the coil, and back to the heater. I guess the only downside is if the heater goes down, I have no hot water. But I have had 2 of these in service for over 3 years with no issues whatsoever.

Heater temp is set to 160 in the Winter (busier), and 140 or 150 in the Summer. This maintains my holding tank at 110-120. (tank t-stat set at 120) Occasionally it will drop to 100-105 if more than 5 bays are drawing hot water. But that seldom happens.

 

[JIMT]

washnvac,
From your last post I assume that the 30 gal tank is closed, you are feeding city water to the bottom of this tank and to the inlet of the Rannai and then you take hot water out the top of the 30 gal tank at city water pressure.
Do you feed the high pressure pumps at city water pressure?
We supply our pumps at atmospheric pressure so they will suck soap and wax.

 

[washnvac]

I assume that the 30 gal tank is closed, you are feeding city

Sorry, I did not specify. The 30 gallon tank is open It is fed with a regular Watts 2 stage float valve with cold city water. It draws from the bottom; same as what you are doing. I have no pressure feeds.

The advantage to my set up is that you do not have to have multiple heaters to feed the bays. The downside is that tank water you are keeping heated; which a lot of guys do not want to do. But I am only heating when bays are timed hot.

I just wanted to throw this set up out there for guys who are worried about that cold sandwich effect, and keeping flow through the heater for proper combustion. My way eliminates all that.

 

[Bubbles Galore]

There is a ton of good information in here about going tankless and from what I'm reading, a 199k btu unit should be more than sufficient for my 6 bay self serve. Would those of you with units agree with that? I was concerned that I was going to have to go multi unit, but this may end up working well.

Thanks!

John

 

[JIMT]

The Rinnai heats the coil only, which in turn heats the water in the 30 gallon tank. It is similar to the "old" way, in which you had a monster boiler looping to an open tank. But here I am able to maintain 30 gallons of hot water with one Rinnai. The Rinnai flow is only 7.5 gallons per minute max. To direct feed and keep up with 9 bays, I would need 3 or 4 heaters. I found it more cost efficient to have 1 heater and to keep a bit of hot water on standby and not to worry about flow restrictions or heater short cycling.

And you are correct, I am circulating from the hot heater outlet, through the coil, and back to the heater. I guess the only downside is if the heater goes down, I have no hot water. But I have had 2 of these in service for over 3 years with no issues whatsoever.

Heater temp is set to 160 in the W inter (busier), and 140 or 150 in the Summer. This maintains my holding tank at 110-120. (tank t-stat set at 120) Occasionally it will drop to 100-105 if more than 5 bays are drawing hot water. But that seldom happens.

Washnvac,
Thank you for the info on your system. We have now done a similar system except the float tank is insulated and only 8 gal. The hot water then goes into a 10 gal electric hot water heater that is used for a buffer tank not heated. The float valve is supplied from this tank. The hot water then goes back to the water pump and heater.
It is working great and we have much more room in the equipment room.
JIMT

 

[mjwalsh]

Naviens???

Anybody have good experience with any on the below link??? We are especially interested in the ones listed with the built in circulator. We will might need a flow check valve on the way to our existing 3 storage tanks. Looks like it could work but the existing enclosed 3 tanks have about 50 - 60 psi of city water pressure going in & out. If Navien's built in circulator can make sure the water keeps flowing properly into the existing tanks we should be OK. This would supplement our other system so it would only activate when the water temperature is not keeping up.

http://www.globalindustrial.com/g/p...-Gas/Navien-Condensing-Tankless-Water-Heaters

Mike

 

[bigleo48]

Just an alternate way to hook the tankless up---I use one single 199,000 btu Rinnai, for a 9 bay s/s. I have a closed loop boiler coil inside a 30 gallon stainless tank, that runs to the Rinnai with a Grundfos circulator.

So you have effectively turned a tankless into a tank...just a little smarter. But how can it help, unless you have short lines to the bays, no mixing tank, etc? Because the 30 gals will need to heat up if it hasn't run for a while and makes its way to the mixing tanks and down the lines to the gun/brush. With presoaks and such at LP, the user would be long done before he got any hot water