tankless water heaters

[N BROWN]

Xiong take it from somebody that has used both Continental Express equipment and tankless water heaters, your calculations are correct. I would recommend that you go with the condensing heaters for the extra gas savings.

[Xiong]

Originally Posted by Howard

Don't do it. These things only make any limited sense if you are in a warm climate AND have no space to install a real hot water heater. They are less efficient than most heaters - costing you more energy per gallon. They have flow restrictions, either restricting flow to your washers or dropping temperature or both. Typically you may need to also install a storage tank which totally kills the reason for installing in the first place, or install many of them.

What you have to do is some math to see what the flow rate could be at any one point in time. If someone starts both of your 40# washers at the same time, just those two machines will probably be demanding hot water at the rate of about 30 gallons per minute - that does not include any of the other machines running. You would need four or five instant units of most brands just to handle that flow without a storage tank. Get a real hot water heater.

thanks howard,
if all my washers start at the same time, the maximum flowrate would be about 96 gallons per minute (360 liters per minute) base on the specs of the machines. do i need to consider this as the flowrate, or can i go higher or lower than this flowrate?

will the incoming water temperature varies from day to day, or is it consistent base on your earth location (due to atmospheric pressure and temperature)?

i have water tanks now, but want to get rid of them to make room for WDF.

thanks again

[Xiong]

Originally Posted by N BROWN

Xiong take it from somebody that has used both Continental Express equipment and tankless water heaters, your calculations are correct. I would recommend that you go with the condensing heaters for the extra gas savings.

thanks

can you be bit more specifics?

what do you mean by condensing heaters to save gas?

pm me if necessary

[Howard]

A condensing heater is one that contacts the exhaust with a secondary exchanger to capture the latent heat through condensation. These units typically have two sets of PVC pipes, one that brings fresh air into the sealed combustion chamber and one that vents the exhaust at about 80 degrees. These units typically have efficiencies of 95% or better, but cost more to buy upfront.

As for sizing you don't need to size for the full flow. You only need to calculate what the hot water flow will be. Further, it is highly unlikely that all your machines would ever demand hot water at the same time. In the real world you probably need somewhere between 30% to 40% of the theoretical max - but this will be different for each store and based on the mix of small and large machines. You most likely will want some sort of storage tank, otherwise you have to install much larger units. Search the board as we have gone through the details of this many times.

[cyclonelaundry@bellsouth.net]

I put in 3 Takagi tankless heaters 6 years ago and tied them together with a module that regulates the usage of each depending on the demand called for by the washers. I haven't had 1 bit of trouble and I like knowing that the water is only heated when it is needed, thus saving energy. It's also nice having the extra storage room behind my dryers.

[Howard]

Originally Posted by cyclonelaundry@bellsouth.net

I put in 3 Takagi tankless heaters 6 years ago and tied them together with a module that regulates the usage of each depending on the demand called for by the washers. I haven't had 1 bit of trouble and I like knowing that the water is only heated when it is needed, thus saving energy. It's also nice having the extra storage room behind my dryers.

But you are wasting energy, not saving it. Instant water heaters are generally lower efficiency than good quality high efficiency units that are 95% to 99% efficient. A well made and well insulated storage tank loses almost not energy. My Natco Super-E units were always cool to the touch due to insulation. If I shut down the units at night the tanks lost less than one degree over night.

[Xiong]

Originally Posted by Howard

A condensing heater is one that contacts the exhaust with a secondary exchanger to capture the latent heat through condensation. These units typically have two sets of PVC pipes, one that brings fresh air into the sealed combustion chamber and one that vents the exhaust at about 80 degrees. These units typically have efficiencies of 95% or better, but cost more to buy upfront.

As for sizing you don't need to size for the full flow. You only need to calculate what the hot water flow will be. Further, it is highly unlikely that all your machines would ever demand hot water at the same time. In the real world you probably need somewhere between 30% to 40% of the theoretical max - but this will be different for each store and based on the mix of small and large machines. You most likely will want some sort of storage tank, otherwise you have to install much larger units. Search the board as we have gone through the details of this many times.

sounds like a complicated system such as the heat exchanger that i had with one of my mats, the the whole system plug up so very tiny drain. it was a headach to bypass that heat exchanger system.

wanted to go tankless, 'cause don't see the major advantages in keeping a tank of hot water when/if no one is washing.

would a system work better if the units are in parallel or in series? if in parallel then temp settings would be the same for the units, but if in series then the temp settings could be different so long as the final output water meet the correct temp to the machines. what would the pros and cons of units being in parallel or in series?

[Howard]

Actually you are best served by having them parallel with a loop back and different temperature settings, re-read what I have written on this before.