Hot water heater argument 1

[ballpeen]

Hello all. I am hoping someone here can answer a question that would seem a no-brainer to me but, not being an electrical expert, I thought I'd pose it here. What it is, the facility where I work is on a electricity usage reduction program and are looking for anyway to cut back. One thing that was brought up was the use of hot water heaters. As it turns out we have quite a few in and around the plant.
The question is, would it be advantageous to replace the 4500 watt elements in most of our heaters with 1500 watt elements? My boss claims that this would save a lot of power. I really don't see it. It would seem to me that it takes a certain amount of power to get a certain amount of water up to a certain temperature. The only thing a lower wattage element would do, in my opinion, is to lengthen the time it takes. Is he correct or am I? Thanks, Ballpeen.

 

[ballpeen]

Thats some good advise given there, particularly waross. As stated my super has said right along that with all of these electrical reductions your only looking at "pennies" and I think after what I've seen for numbers he's probably right.
Yes, there is talk of doing a cogenereration in conjunction with our steam boilers but, again my boss says you need a cooling tower to keep a constant vacuum on the discharge side and engineering doesn't think its needed. We'll see how it all works out in the end.
Itsmoked, I work in the maintenance dept. of a textile plant. As an assistant to the dept. manager. I'm the guy that usually ends up on all of the projects that my boss doesn't want to do, and this electrical reduction is one of them.
As far as the rate structure, that is constantly being worked on from what I understand.
No, we don't have natural gas there. We primarily burn wood and use #2 fuel oil as a backup. And no, we really don't have a lot of A/C or refrigeration either. One thing that we do is take our hot waste water and use it to preheat our process water and we also have a couple of water cooled air compressors that also preheat water and those work quite well. Although the heat exchangers keep having the tubes go bad, but thats another story altogether.

 

[itsmoked]

I hear you waross.. I drove over to the next town (30min) and bought an demand gas water heater when our old 50gal started leaking. Got back and started reading the manual..

1) Water lines came out the bottom... Not an insignificant change to existing plumbing.
2) Required a 6inch flue. Up from exiting 3 inch?
3) Required a 1 inch gas line from metering point!!
4) Wouldn't come on at less than 3/4 gal/minute.

I took it back.

It costs about 37.5millicents to raise a gallon of water a degree F. So carving a bunch of degrees out of water heating by preheating is a great spot to start.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[jraef]

ballpeen,
First off, I'll reiterate the comments about hiring an expert on this. $1 million is a lot of money as an increase, even a 10% recoup in the first year would more than pay for the consultant.

For example, like others I would also suspect power factor penalties. The peanlties often work out as multipliers on your basic rate, so even if appears that they have negotiated a good rate for you, they jack the net dollars up by sticking you with a big penalty for poor pawer factor. I'm not bashing the utilities here, power factor costs are very real to them, but often they are in the business of selling you on THEIR solution, which is for you to pay for thoses costs, rather than mitigate the cause. You mentioned using cooling water from large compressors to preheat process water. Large facility compressors are often a good candidate for running synchronous motors as synchronous condensers to improve the power factor of the entire plant. Not cheap, but possibly a quick payback if you are getting hit with big penalties.

There are also very (relatively) low cost Demand Reduction Systems that act as energy watchdogs, monitoring and mitigating your peak demands, another utility rate multiplier, by shedding loads on a prioritized basis.

Getting an expert on board to investigate your needs and suggest the myriad possibilities would be well worth it. Fluorescent light bulbs and water heaters are not ging to make much of a difference in a $1 million anual increase I'm affraid. Not unless you have about 4 million incandescent bulbs!

Good luck with that.

Eng-Tips: Help for your job, not for your homework Read faq731-376

 

[RobWard]

We've been looking hard at energy savings too. A 60% increase in electricity prices kind of impacts the bottom line.
We're a teeny tiny factory in comparison to most people here I would guess, and the cost of changing things just wipes out any payback. We tried looking at cogen but our processes just aren't suitable as our ovens high grade heat, not low. Solar and wind are so expensive and difficult to integrate that we'd never ever recoup the cost.
All the seminars we can go to ever tell us to "turn off the lights in empty rooms, and shop around for your supplier. No sh*t Sherlock!
All we can do practically is to add insulation to everything to reduce heat losses in the process.
No environmental grants available for us to help us do it either. (The Government must have spent all the money on their £500,000 shiny new walkway.)

So I'd agree: lag everything you can, and see if you can reduce the temperature of the water for hand washing (and the processes too: even 1 degree C reduction will help)

Rob

"I love deadlines. I love the whooshing noise they make as they go past." Douglas Adams

 

[VEBill]

"...on-demand water heaters can be located very close to the point of use..."

This implies that one might have several on-demand heaters distributed around the facility (or, for home use, around the house). Sounds like a good idea. But...

Each 7kW unit probably draws about 30A from a 240v feed.

For home use, if you have one appliance (a dishwasher for example) filling with hot water, one person taking their morning shower and a couple of people decide to wash their hands in different washrooms, then you're looking at an instantaneous current draw of perhaps 120A (240vac). Add in some other loads (like space heating and a water pumps) and your 200A service suddenly starts to look inadequate.

In other words, for home use, the advantage quoted at the top may not be as practical as it might appear.

And for facilities, such uncontrolled peaky loads might be the exact opposite of what is required to reduce the electricl bill.

There are small (eg: 5 or 10 US gallon) 'normal' water heaters that can provide another solution with fewer drawbacks. And they're much cheaper to boot. Might be ideal for isolated bathroom sinks.

 

[itsmoked]

Hey RobWard do your ovens have stacks with heat exiting?

Just curious.

Keith Cress
Flamin Systems, Inc.- <

http://www.flaminsystems.com>

 

[stevenal]

A further possible problem when changing elements is finding the flange underneath is composed of rust. Old element kept the rust in place and prevented leaks, but the new one will never seal. The cheap job has suddenly become expensive. Here's a link to a very efficient water heater that solves the rust problem too.

http://www.marathonheaters.com/

 

[waross]

A quick fix for under utilized tanks is to remove one of the jumpers to the bottom element. It has the effect of reducing the effective volume of the tank. It is quick, there is no problem with rust, there is nothing to buy, and if the jumpers are saved it is quickly reversible.
I don't offer this as a solution, but rather offer it on the theory that if management is going to do something with a small probability of success, let's steer them to something cheap and reversible (If you can't make your boss look good, try to keep him from making himself look bad). It will almost certainly reduce consumption and there are almost certainly going to be enough complaints that it will be reversed. Myself, I would probably suggest it to management on that basis. However I have virtually no corporate survival skills whatsoever.
And what the hey. In a big plant there are probably several tanks that are under utilized and would profit from this kludge.
yours

 

[RobWard]

Itsmoked,

no they don't. (Well, not intentionally anyway)

Back to water heaters though; you mentioned these in another thread I started asking about generators:

http://www.whispertech.co.nz/main/acwhispergen/

2 birds, 1 stone...

I wonder if they'd be of any interest to th O.P.?

&quot;I love deadlines. I love the whooshing noise they make as they go past.&quot; Douglas Adams

 

[waross]

Hello RobWard
Here's a web site that may be valuable when evaluating sterling cycle devices (As in the link above.)
The web site information appears to be about 4 years old and may be out of date. It will give you the questions you will want answered when evaluating a sterling engine, and hope that new developments have changed some of the answers.
Yours

 

[jraef]

Still, how many water heates are we talking here?

Let's review Econ 101; "run the numbers before taking action". If all your heaters were reduced from 4000 to 1500W, each ran only 2 hours per day cumulatively, 365 days per year and you pay 10 cents/kWH, you would save $219/yr per water heater. You need to have 4566 water heaters to end up saving $1,000,000/yr, and of course the first year you would have to suck up the $100 guesstimate for parts and labor per heater, which comes to a whopping $456,000 initial outlay. I still say you have bigger fish to fry first. Play with the little stuff after you make a big dent in that increase.

Eng-Tips: Help for your job, not for your homework Read faq731-376

 

[waross]

I don't know how I missed the reference to steam and co-gen.
Re the cooling towers. The answer is yes, no, and maybe.
It depends on the whole layout.
I'll try to give you an over view so you can talk intelligently.
There are two types of steam turbine, (I have allready commited a faux pas because there is also a third type that combines the first two but later for that).
A condensing turbine typically takes steam at boiler pressure and discharges into a vacuum. This needs a lot of cooling and a water tower is a good way to provide the cooling but not the only way.
A non condensing turbine typically takes steam at boiler pressure and discharges steam at a lower pressure. No cooling needed. A 150 psig boiler may feed a noncondensing turbine that discharges steam at 15 psig for use in a drying cycle. This type of turbine may often be bypassed with a desuperheater which is cheap and simple and will convert high pressure high temperature steam into low pressure low temperature steam. If your turbine goes down, your other process continues without interuption. Also, if your process demands more steam than the turbine can deliver the desuperheater can be configured to automatically kick in and supply the excess steam again without interuption to your process.
The choice depends to a great extent on what you have in place, the availability and cost of fuel, the availability of capital, and your intended mode of operation. If your boilers have more capacity than you are using you may opt to just use the excess capacity to generate part of your electrical needs. With an assured supply of cheap fuel, you may opt to go new higher pressure boilers and supply all your electrical needs, or generate and sell an excess.
The third type of turbine is a multi stage turbine that supplies steam at one or more intermediate pressures and condenses the balance.
In addition to a cooling tower, a river or a lake may be used for cooling water. Watch out for environmental issues because of the increased water temperature of the river or lake. I read a paper on a co-gen plant whose output was limited by the allowable temperature rise of the stream they used for cooling. When the water flow was down they had to curtail generation to avoid heating the river over the limit set by the local environmental board. I read about a nuclear plant whose discharge of warm water into a lake gave rise to an explosion in the mussel population in the vicinity of the discharge.
In a sawmill environment, lumber can be pre-dried by placing it in front of the air discharge from radiator type coolers, but that's a poor mans solution. Either poor in capital or in water for a water tower.
I hope this is enough information for you to interface between your boss and the engineering staff or at least ask intelligent questions.
yours

 

[ballpeen]

I didn't realize that you had a non-condensing type of steam turbine available. That looks like a viable option. Maybe thats what our engineering dept. is looking at right now? Based on what my boss is saying, he evidently isn't aware of them either.... There is a river nearby but, this company is dead set against any discharges into it. Even if they are benign. What they want is a "closed loop" way of thinking, where we actually throw nothing away, if you get my drift. Heck, if we do have a spill, its a major event.
One thing that is going on at this plant is that the facilities engineer and my boss, (a master electrician and maintenance dept. head), have what seems to be an ongoing feud. Its a long story but, each of these guys are constantly trying to prove each other wrong. Usually the engineering guy comes out on top as he has the upper management on his side, even if the outcome doen't make a lot of sense. I have to be careful what I say because I can get my boss in trouble very easily.
Of course, we are using a wattage meter to check our H.W. heaters to see just what they are consuming. That way we can make a sensible decision as to what our best options are. Whether to put timers on or just wrap them with insulation. Removing the jumpers are something that I haven't heard yet. Do all these heaters have them? I'll run it by the boss first and get his input on it. I know what you mean stevenal about the element removal, sometimes its a nightmare.
I am not sure if they have checked into hiring an energy consultant or not. It probably would be worth while, but all I can do suggest it. Actually hiring this person would ultimatly be up to someone higher up the food chain.
One thing I'm sure of is the monitoring of the power factor. And it runs close to .80 to .90 as a rule. Where the cloth is woven, the room where the disconnects are, there is a digital readout that tells the P.F. constantly. And I've been told there is a large bank of capacitors where our power comes in to another building to offset the large motor loads we have there. I'm not sure how that is monitored in this other building, but there must be a way. I'll ask about that and see what my boss says. Regards, Ballpeen.

 

[waross]

If you are using large industrial; water heaters this will probably not apply, but for residential heaters there are typically two elements each rated at the rating of the water heater. The upper heater comes on first on a fixed thermostat. This warms the water in the upper 1/4 or less of the tank very quickly to give fast recovery. When the upper thermostat reaches it's set point, it transfers the current to the bottom element that heats the rest of the water. This is the element with the adjustable thermostat.
An indication of a failled lower element is hot water available quickly but it runs out quickly.
respectfully

 

[RobWard]

Waross,
could you post a link to the site regarding sterling cycle devices, please?
(Sorry for the unintentional thread-hijack folks...)


Kind regards,

Rob

&quot;I love deadlines. I love the whooshing noise they make as they go past.&quot; Douglas Adams

 

[waross]

Hi RobWard
Sorry about that. I don't know how I lost the URL when I posted. Some of the problems with Sterling Engines mentioned on this site may have been resolved by the Wispertech people.

http://www.stirlingengine.com/faq/one?scope=public&faq_id=1

yours

 

[RobWard]

Thanks Waross

Very interesting read.

Rob

&quot;I love deadlines. I love the whooshing noise they make as they go past.&quot; Douglas Adams

 

[2dye4]

its pretty simple

Either you heat the water or you don't

takes same energy to heat the water up 20 C no matter
what the source.

 

[VEBill]

"...no matter what the source."

Some sources are cheaper than others. Also, a given source might be cheaper depending on when you use it.

So, it's not necessarily a matter of saving energy; it's a matter of saving money.