The Secret Formula for Heating Your Water

[Adamski]

Guys,

I want to bring your attention to the excellent article written by Jeff Deal about how to size a water heating system for a laundromat. This article takes into consideration all the pertinent factors necessary to properly size a system. You can find Jeff's article on this website under the "Utilities" heading. The name of the article is: "The Secret Formula for Heating Your Water". Read it carefully as it is complex.

[epic02]

Larry, Nice Avatar ahh.
I just finished reading his article in the new Planet Laundry Magazine.

[merlin3]

Larry,

Jeff is an extremely knowledgeable guy and very personable at that. I met him at the FREE two day service school Hamilton puts on for owners of their equipment.

I know Hamilton has gotten a few bad knocks around here in the past, but I have nothing but good to say about them. I have their units in two of my three stores and am extremely happy with them.

Randy

[Adamski]

Kenny,

I was kind of intimidated about this Avatar stuff but I decided to give it a try yesterday and come to find it - it was really quite easy to do one. One just has to find a picture on your computer that would work and write down the file name of that picture. Then go to "User CP" and find the Avatar section and use the search feature to locate the same picture. Couldn't be easier.

[Howard]

Larry, I think it is a very good analysis, much better than what most vendors do - but I think it will still result in over sizing. We all have to remember that Jeff wants to be certain customers don't come back and complain they are running short of hot water, so I assume there is excess capacity built into the analysis. I wrote a reply to the posting, but have not gotten any feed back yet. Here is what I wrote:

"Jeff:
You have provided the best analysis of correctly sizing a water heater that I have ever seen.

My gut tells me that this methodology will get you closer to a correct sizing than what most companies use, however it will still tend to oversize the system. The reason I believe this is today's washers typicall only use hot water during the main wash (perhaps prewash) and not during the rinses. Further, it is highly unlikely that all washers will start at the exact same time. Thus, the demand will be much more evenly spread over the hour as only a small percentage of washers are likely to be in the fill portion of the wash cycle at any given time."

[Adamski]

Howard,

Yes, I read your reply which was attached to the article.

Please notice that the last 2 paragraphs in the article refer to making a final adjustment for customer wash preference. This means we are to determine what percentage of our cycles are HOT vs WARM vs COLD water cycles and then multiply by a percentage to account for the fact that not all cycles are HOT cycles.

After carefully studying the entire formula, I cannot find any over-stating of sizing requirement like I fully expected to find. I must say, I think it is a very good formula for laundromat operators to rely on.

[Howard]

That is not was I was talking about. The issue is that the machines will not all be in the wash cycle at the same time. The odds are that why one is in the wash cycle one is in the first rinse cycle, one is in the second rinse, one is in extract, one is being loaded, and one is sitting empty.

Or put another way if you had three machines that needed 20 gpm during that wash cycle, you would not need 60 gpm of capacity as it would be unlikely all three would be drawing water at the same time. Well with three machines it is possible, but with 20, 40, 60 or so machines you get the point.

[Adamski]

Howard,

I'm not sure the staggered draw applies because the water heater does not replace the expended hot water instantly. It takes minutes to reheat the hot water that left the tank whether that water left at the rate of 20 gal in 5 minutes or 60 gal in 5 minutes.

[Howard]

No. If you pulled 20 gallons out in 5 minutes you dumped 20 gallons of cold water in the tank, if you pulled 60 then you dumped three times the amount of cold water, thus dropping the tank temperature that much more.

Look at it another way, if you have a 300 gallon tank and have 300 gallons of demand in an hour it makes a very big difference if that demand is at 5 gallons a minute constantly over the hour versus 60 gallons a minute for 5 minutes.

[Adamski]

No. If you pulled 20 gallons out in 5 minutes you dumped 20 gallons of cold water in the tank, if you pulled 60 then you dumped three times the amount of cold water, thus dropping the tank temperature that much more.

Look at it another way, if you have a 300 gallon tank and have 300 gallons of demand in an hour it makes a very big difference if that demand is at 5 gallons a minute constantly over the hour versus 60 gallons a minute for 5 minutes.

Howard,

How would you propose to adapt the formula to account for the staggered demand?

[Howard]

I would imagine that one could base it on measurements of systems they install in real world laundromats. Jeff should be able to document how much excess capacity actually exists in stores where they use this formula.

I know when I specified my water heating equipment I went through calculations very similar to what was proposed in the article. I think I then downsized by at least one-third. I remember two distributers insisting that I needed three units when I told them two would do. I installed two and have never had a problem.

This issue is much more of a factor if you install instant hot water heaters with no storage tank, as many of them restrict flow rate which would adversely effect fill times. In my system I have a pair of Natco Super-E units with a recycle loop where cold water gets injected into the recycle loop. At first it made no sense to me, but after studying the design it actually works very well.

[tekixhunga]

seems like that entire piece was lifted (at least it is very similar to) from here: http://www.ajaxboiler.com/?page_id=251

[merlin3]

seems like that entire piece was lifted (at least it is very similar to) from here: http://www.ajaxboiler.com/?page_id=251


Or maybe that entire piece was lifted from here: Link to article (http://www.planetlaundry.com/utilities/2011/secret-formula-heating-your-water) http://www.forums.woodnet.net/ubbthreads/images/graemlins/raised.gif




:D

[Xiong]

thank you for the reminder :)

very good stuffs....though I thought I'd to dig for my notes on fluid mechanics and thermodynamics, but guess not :D


Guys,

I want to bring your attention to the excellent article written by Jeff Deal about how to size a water heating system for a laundromat. This article takes into consideration all the pertinent factors necessary to properly size a system. You can find Jeff's article on this website under the "Utilities" heading. The name of the article is: "The Secret Formula for Heating Your Water". Read it carefully as it is complex.

[itsaplane]

This discussion is very timely for me as my circa 1997 Teledyne Laars "Mighty Therm" boiler's heat exchanger just started leaking. The jury's still out on the fix (new $4k heat exhanger) or buy new (let's me move from efficiency in the low eighties to something higher at a higher current cost) decision.

Once again, it's making me wish we had a Consumer Reports type article to help me with this decision -- and to see what boiler systems are the most desirable.

My decision parameters are:
- speed to resolution - there's no hot water in the 'mat now (51 washers - toploaders to a 75 pounder)
- cost
- future reliability (and redundancy that certain systems like Hamilton's EVO Duo provide)

So, I once again turn to the CLA brain trust. Opinions, articles, experience?

Thanks,

Eric

[Hot H2O Guy]

Hello all,

I'm a new member to this board, and this is my first post. I'm also an owner of a coin laundry in Van Nuys, CA.

After working for manufactures of commercial water heaters such as Raypak, Laars and Lochinvar for the past 30 years, I decided to buy my own laundry and work with local customers to help with their hot water needs in S. Calif. Traveling and Training for the past 15 years as a Regional Manager has lost it's luster, and I now own and operate a coin operated laundry. I also work for a local Distributor who specializes in commercial and residential water heating products. I'd like to weigh in on the recent acticles published by Jeff Deal of Hamilton Engineering. First of all, I think Jeff is right on in his thinking. Tankless heaters have their place in this world, but there are some dump load applications out there where you just cannot deviate from a hot water storage tank. Coin laundries are one of these applications where you cannot get away from a tank and expect your customer to get the wash that they bargined for when the laundry is busy. Of course you could add more tankless heaters to the bank of heaters that you already need have in this type of modular system and get the job done, but then the number of units needed just get silly. There becomes a point that adding some thermal storage simply makes more sense. Also, the dollars and cents of adding more gas appliances that require service vs a properly sized tank that does not need much attention, needs to be considered.

When I look at all the sizing data published the manufactures of water heating equipment, it just does not seem to fit the needs of the modern coin-op laundry. I find that the formulas either assume all top load washers or the larger front loaders used in OPL applications that may have multible washes that use hot water. The best approach to sizing any coin-op laundry is to consider the amount of hot water used by each machine, and determine a total gallons per hour required needed to keep up with demand during the busy times.

I have been using a simple formula for years with success. I have taught many of the salespeople who work for the Distributors, as well as many owners, how to size water heaters for coin-op laundries. Here it is in a nutshell.

First, determine the warm water requirements of each type machine in the laundry to be sized. Why warm? Because some customers use hot, and some use cold. Warm represents an average number of gallons used per cycle. If you feel that the demographics of your laundry indicate that your customers always push the hot button, than use the hot water number. However, I have found that the warm water usage information that I have gathered over the years has worked well for calculating the total GPH per cycle, and that nobody has ever come back to me and complained that they were running out of hot water during the busy times.

Once the total gallons per cycle number is added up for all the different types of washers in the store, the number of cycles per hour per machine needs to be considered to calculate a total GPH (gallon per hour) requirement. I have always used a factor of 1.5 cycles per machine. In my laundry, some of my washer cycles are longer than 30 minutes. If you consider the time required to load, unload and add soap, softner ect., than one and a half cycles per hour per machine is a reasonable expectation for turns for each machine. Now that I'm an operator of my own laundry, I would be happy as a clam if I could have every machine in my laundry doing one and a half turns per hour at the same time. This represents the peak load period, and we need to select a heater that will recover at least this total amount in GPH.

Lets review with an example of a store that I have sized before.

Qty. Type Gallons of Warm Water Gallons per cycle

10 Top Load 9 90
16 25 lb. 9 144
6 50 lb. 19 114
2 75 lb. 56 56
_____

532 Total gallons per cycle

If you add the gallons per cycle for all the machines, you would need 532 GPH total for one cycle of all the washers. Multiply this times 1.5 cycles per hour, and you have the total GPH needed for this laundry example. 532 x 1.5 = 798 GPH

You now need to refer to the GPH data published by the water heater manufacturer that you would like to use. Here in So. Calif. we use the 80 degree rise colume for the heater selection. Why the 80 deg. rise? Because our ground water is 60 deg. in the winter, and the Health Department requires that we maintain our tank setpoint at 140 deg. That represents an overall rise of 80 degrees in the temperature of the water. In colder areas of the Country where the city water is 40 deg. in the winter, a 100 deg. rise in the water temperature rise needs to be considered when selecting a heater size.

Getting back to my example, here in So. Cal, many customers prefer to use the Raypak Hi-Delta heater for their laundry. When I look at the spec sheet for an 80 deg. rise, I can see that a model WH652 will recover 837 GPH. This meets or exceeds the needs of the store used in the example above.

As far as the size of the storage tank is concerened, a typical thermal storage tank needs to contain at least 20% of the total GPH required in tank volume. Our example above required 798 GPH, and 20% of that is 160 gallons. This a minimum amount of storage, and in many cases the tank is larger.

I would say that I agree with Jeff Deal in his recent articles in Planet Laundry with respect to system sizing of coin-op laundries. He uses the hot water numbers for each type of washers, and then applies a diversity factor based on the size of the store. I use the warm water use numbers for each type of washer, and apply the diversity factor up front. I think we both agree that tankless heaters will not maintain a stable delivery temperature during the peak load periods, and are not the best choice for this dump load application.

I welcome any comments or questions that you may have.

Kevin Trent
Austin Industries
(714)319-7417

[Hot H2O Guy]

Eric,

Is the hot water back on? I'm a new owner of a coin laundry, but I have worked for water heater manufacturers such as Raypak, Laars and Lochinvar in my 30 year career prior to purchasing my laundry. I have taught many how to size, and today there are many fine products available.

I agree with Jeff Deal and his recent articles in Planet Laundry when it comes to the subject of tankless water heaters not being to keep up with demand during the busy times. I use a simple formula that considers the various sizes of washers in your store. I would be happy to share it with you. Can you tell me about the mix of washers in your laundry? How many top loaders, front load washers, quanities and sizes?

There are good, better and best choices of equipment to consider.

Regards,
Kevin

[STOUT]

Kevin;

It appears that you are not in favor of tankless units. Since several members have them and are using them well, what are the conditions it would be an advantage to have over the water holding type you use to market?

[Laundry_Mike]

Kevin;

It appears that you are not in favor of tankless units. Since several members have them and are using them well, what are the conditions it would be an advantage to have over the water holding type you use to market?

The tankless units seem to work in warmer areas, but not so well in colder climates.

[Jefflange]

http://www.htproducts.com/munchkinvwh.html

I run these Munchkins and have had no problems yet.

http://kscdirect.com/item/MUN%2B199VWH%2BASME/HOT%2BWATER%2BPRODUCTS%2BLLC_Munchkin%2BVWH%2B96%2 525%2BHigh%2BEfficiency%2BHot%2BWater%2B%2BSupply% 2BBoiler%250A

[Jeff Deal]

First, thanks to all of you for your kind comments, believe it or not, I wrote the original version of that article back in 1979, when it was published by the other laundry magazines (the Journal and Planet Laundry did not exist at that time).

The one point that seems to missed (and it was not an issue in 1979), is that there are DRAMATIC differences in washers and water usage, let alone hot water usage. As mentioned, same brand, same pound capacity can be as much as 50% different in water usage. So, you NEVER want to use a rule of thumb. Assuming 1.5 loads per hour can also get you in trouble, many machines that were the early top load size front loading machines had cycle time of up to 42 minutes and some manufacturers have 22 minute wash cycles.

As to Hot versus Warm versus Cold, we have seen many stores that operate at or near 100% hot and a few that are at or near 25% hot (based on typical clientele for the store location) Of course the highest percentage are a good blend of hot and warm comprising 80% of the users and 20% are cold, but who is to say what your store has as clients and what their usage habits are? Only the store operator has the ability to tell that.

As to how many are filling at one time as hot, warm or cold, only a genius can figure that out. There are literally millions of possibilities and they vary by the second. There are 3 fill cycles and up to 5 fill cycles, there are some that still have a hot or warm rinse (although most are cold after the first fill) and some that on a hot setting would be hot on the first fill and warm on the second and cold after that, it really is impossible to tell.

The only sure thing, is to, by specific machine, calculate maximum usage and then apply the diversity factors that apply to your specific store, then you will not run out on your peak days and you will not be oversized either.

Hope this helps!

[merlin3]

Looks like I was probably right. :cool:



...I wrote the original version of that article back in 1979


seems like that entire piece was lifted (at least it is very similar to) from here: http://www.ajaxboiler.com/?page_id=251


Or maybe that entire piece was lifted from here: Link to article (http://www.planetlaundry.com/utilities/2011/secret-formula-heating-your-water) http://www.forums.woodnet.net/ubbthreads/images/graemlins/raised.gif