TANKLESS WH LOSS
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Don't yell. Can hear you just fine but don't really understand what you are asking.
Tankless WH don't reduce PSI. there might be a little flow loss which would be the volume and the psi has a direct relation to the flow.
pressure drop usually occurs when some type of demand is put on the system like opening a faucet or flushing a toilet.
If you have a 3" line with 50 psi and you open a 1/2" port you're not going to notice much of a PSI drop, but if you open a 2" port then there will be a significant pressure drop.
If you're asking about flow then it all depends on size of piping and the amount of demand you want to achieve. .
That's why high demand commercial water heaters have 1 1/2" to 2" inlets and outlets to meet the flow requirement.
When you say tankless there are all kinds of tankless water heaters. and they are sized according to demand requirements
Tankless WH don't reduce PSI. there might be a little flow loss which would be the volume and the psi has a direct relation to the flow.
pressure drop usually occurs when some type of demand is put on the system like opening a faucet or flushing a toilet.
If you have a 3" line with 50 psi and you open a 1/2" port you're not going to notice much of a PSI drop, but if you open a 2" port then there will be a significant pressure drop.
If you're asking about flow then it all depends on size of piping and the amount of demand you want to achieve. .
That's why high demand commercial water heaters have 1 1/2" to 2" inlets and outlets to meet the flow requirement.
When you say tankless there are all kinds of tankless water heaters. and they are sized according to demand requirements
Mr David
in Hydro calc , I put zero loss
but the plan checker corrected that
tank less makes considerable pressure loss in the system
Its flow rate. Tankless can only supply certain GPM at whatever temp rise. Thats why i caution people on tankless, 55 temp rise at 2.5 GPM kind of thing.
FishScreener
Well-Known Member
All water heater, regardless of type, have head loss at flow, that’s just physics. All heaters have a rated temperature rise at a given flow. Tankless units by their design have a higher head loss at a given flow, and higher temperature rise at a given flow than a tankless style.
That stated: Unless your limited in space, or have extreme demands, the higher initial cost of the tankless can not be recovered in its life cycle. The increased efficiency of the tank type, has made this comparison more in favor of high efficiency tank type heaters.
I’ve pulled them out of most of the buildings I manage. They are far harder to drain completely for the winter, (if you try to blow them out with compressed air, it overspins, and kills the flow sensor, oops there went a $450 service call, and a week wait for the replacement part). The heat exchanger failed the next year because it didn’t drain completely.
The only place I still have them is the shower units for the fire camps. 30 to 100 filthy sweaty, smokey, people trying to shower in a two hour period in the evening. An extreme high demand event, which is extremely intermittent. The auditors get antsy every time I buy two gallons of “Everclear” grain alcohol to flush them out, and winterize them.
That stated: Unless your limited in space, or have extreme demands, the higher initial cost of the tankless can not be recovered in its life cycle. The increased efficiency of the tank type, has made this comparison more in favor of high efficiency tank type heaters.
I’ve pulled them out of most of the buildings I manage. They are far harder to drain completely for the winter, (if you try to blow them out with compressed air, it overspins, and kills the flow sensor, oops there went a $450 service call, and a week wait for the replacement part). The heat exchanger failed the next year because it didn’t drain completely.
The only place I still have them is the shower units for the fire camps. 30 to 100 filthy sweaty, smokey, people trying to shower in a two hour period in the evening. An extreme high demand event, which is extremely intermittent. The auditors get antsy every time I buy two gallons of “Everclear” grain alcohol to flush them out, and winterize them.
That info is most likely listed in the tech manual / specs for the particular equip your plan has spec’d out.
your answer to this question is still pending , mistery
Diehard
In Remembrance
HI
WHAT IS APPOXIMATE/ESTIMATED PSI LOSS OF GAS TANKLESS WATER HEATERS ?????
THANK YOU
As Mr_David Pointed out your best bet is to check with or get literature from the makers of the unit you have in mind. Different capacities and different Mfrs, would be different.
Basically pressure loss is based on the rate flow through a particular size pipe, with a known coefficient of friction. So of course with no flow, there's no friction loss and no pressure drop. The higher the flow, the higher the pressure loss.
Here's an example from a Hubbell gas fired unit.
EDIT: BTW...What are you doing with HydroCalc?
WHAT IS APPOXIMATE/ESTIMATED PSI LOSS OF GAS TANKLESS WATER HEATERS ?????
THANK YOU
As Mr_David Pointed out your best bet is to check with or get literature from the makers of the unit you have in mind. Different capacities and different Mfrs, would be different.
Basically pressure loss is based on the rate flow through a particular size pipe, with a known coefficient of friction. So of course with no flow, there's no friction loss and no pressure drop. The higher the flow, the higher the pressure loss.
Here's an example from a Hubbell gas fired unit.
EDIT: BTW...What are you doing with HydroCalc?
Last edited:
Diehard
In Remembrance
Is an answer to your question still pending. Or is it still mystery?
Richard Gavle
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Do some/all, tankless heaters have a valve in the water line that "throttles" water flow based on the amount of heat demand at a given time? Or are they (by design) always able to keep up with the demand? Or in the event of not enough BTU available per gallon of flow, does the temperature simply drop past certain flow rate (like a tanked unit after the tank reserve has been compromised)?
FishScreener
Well-Known Member
I’m not aware of any that throttle the flow to maintain temperature. But then, I don’t like them, and only install them in very special circumstances. So, there are a lot I’ve never looked at.
I only have propane, or electric available. So that tilts my numbers a bit. But even out in the rest of the US, they always had a hard time saving enough energy to offset the difference in a twenty year life cycle to pay the difference between the initial costs of a tank type.
And with the newer standards for energy efficiency of the tank type, the comparison shifted overwhelmingly to the tank type.
I only use tankless in things like shower trailers, which have extremely erratic demands. A six unit shower trailer, may see forty to sixty showers in two hours. So, the hat water runs continuously, and then may not see more than six showers per day, for the next week.
The extreme peak makes it almost impossible to meet the peak with a tank type. And due to the mobile nature of the system, you are limited to propane as the energy source. Plus, this is a mobile installation, and weight and space become critical. So, this is the only application where the tankless pencil out
I only have propane, or electric available. So that tilts my numbers a bit. But even out in the rest of the US, they always had a hard time saving enough energy to offset the difference in a twenty year life cycle to pay the difference between the initial costs of a tank type.
And with the newer standards for energy efficiency of the tank type, the comparison shifted overwhelmingly to the tank type.
I only use tankless in things like shower trailers, which have extremely erratic demands. A six unit shower trailer, may see forty to sixty showers in two hours. So, the hat water runs continuously, and then may not see more than six showers per day, for the next week.
The extreme peak makes it almost impossible to meet the peak with a tank type. And due to the mobile nature of the system, you are limited to propane as the energy source. Plus, this is a mobile installation, and weight and space become critical. So, this is the only application where the tankless pencil out
Jamesplumbing06
Well-Known Member
When the heater was installed. Was it installed in a copper system and then someone added crimp pex to install heater? Loss of visual pressure/flow.
Or do you have enough gas? Most units require 3/4”-1” dedicated supply. If the unit can’t maintain your temperature to demand. The heater can slow down flow to raise temp.
I guessing your anger and abrupt question means it was just installed and a non pro overcharges u and never returns.
Or do you have enough gas? Most units require 3/4”-1” dedicated supply. If the unit can’t maintain your temperature to demand. The heater can slow down flow to raise temp.
I guessing your anger and abrupt question means it was just installed and a non pro overcharges u and never returns.
Diehard
In Remembrance
Wow! Some of these questions sure take off on tangents, don't they?
The OP left the scene weeks ago.
The OP left the scene weeks ago.
Richard Gavle
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I was just trying to learn something about on demand heaters.
It appears from Jamesplumbing reply, that (contrary to fishscreeners reply) they may indeed have some type of valve on the water line to throttle the flow to meet temperature demand when needed.
What's your take on this Diehard.
As to the OP.... he seems kind of hard to deal with, since as MrDavid and you have pointed out, obviously different heaters (regardless of whether they use a valve or not) would supply different restrictions at a given flow.
It appears from Jamesplumbing reply, that (contrary to fishscreeners reply) they may indeed have some type of valve on the water line to throttle the flow to meet temperature demand when needed.
What's your take on this Diehard.
As to the OP.... he seems kind of hard to deal with, since as MrDavid and you have pointed out, obviously different heaters (regardless of whether they use a valve or not) would supply different restrictions at a given flow.
Diehard
In Remembrance
Yeah I wish the OP's were required to respond and close out a question, one way or another.
Let me first say that I don't have a lot of experience with them. I did specify many types on my Industrial and Municipal design projects(not a plumber) but never got into very much detail. Basically just looked at what they could deliver at various flow demands.
My first thought(guess), on flow control, was that they did not use any. I assumed that if the demand was greater then what the unit was designed for, or could deliver, then it fell short of it's temperature expectations. I'm not even sure at this point in time if they're required to have tempering valves, for safety reasons. (I've been retired for awhile now.)
So I did do a little googling on this, out of curiosity, and didn't find much yet. I did see some references to flow control valves but not sure if it was part of the package or something one would add to avoid over taxing the unit. For example a simple manually operated flow control valve similar to the one I put on my potable hot water system running off my limited tankless water heater on my heating boiler.
The best and fastest way to get good information is to call the manufacturers. I might just do that, just for the hell of it.
Jamesplumbing06
Well-Known Member
I forgot to mention my brand of experience is Rinnai. I seen an eBay special the other day that had a manual flow restriction valve. But never never order an eBay special. No u l safety listing at all. I don’t know what an op is so not sure about that.
Diehard
In Remembrance
OP = original poster
The individual who started the thread.
Jamesplumbing06
Well-Known Member
Gotcha. I will know what op is now. See ya on next one
Threads do that sometimes. The OP started it, never to be heard from again,but an interesting topic takes off on its own path
I always get this correction time from Los Angeles city plan checkers,
no matter what type tank less used, they go with demand of maximum of hot water usage;
they look the manufacturer catalog/ spec and figure out the pressure loss which is to high
and the pressure loss shoul be considered in conducting hydro-calc for available pressure in the system.
