Steam heated water heater

[ballpeen]

Hello all. This may sound a little off the wall but, would it be practical to use existing steam from a production boiler to heat a small tank of hot water. In other words replace an electric one with a steam heated one? What it is, our plant is doing an electricity reduction project and this is something that was brought up.
Maybe this has already been done,I am not sure. I know it probably would be kind of costly with buying the tank and the pressure reducing stations and associated piping but, once thats all done its, for all intensive purposes, free hot water. I figure the demand on the steam system would be negligent as it would probably run at a low pressure, 5 to 10 lbs. maybe.
Does anyone know the safety ramifications of this? I don't think our engineering dept. would go for having something thats going to explode in the future. So it will definitely need some safeguards installed for that possibility.
Anyway, what do you guys think? Thanks, Ballpeen

 

[MintJulep]

Not off the wall at all, very common.

Depending on your use you may even want to look at an "instantanious" water heater. No stand-by losses associated with a tank.

 

[willard3]

snip
Does anyone know the safety ramifications of this? I don't think our engineering dept. would go for having something thats going to explode in the future. So it will definitely need some safeguards installed for that possibility.
snip

Require preperly-rated ASME stamped pressure vessels and the explosion problem is under control.

Do steam maintenance regularly.

 

[quark]

They are very common and with the competence of running a boiler, your engineering department shouldn't have any problems in going for something thats going to explode in the future. Like suggested earlier, go with the correct design.

You can think of going with direct steam sparging to gain the sensible heat of steam also.

 

[katmar]

I agree that this is a fairly common practice. On the installations that I have done I did not use pressure vessels. If you want the hot water for washrooms and showers you will not have the water boiling and you can use a simple vented tank.

The level and temperature controllers can be anything from simple self-acting units to fully fledged control loops, depending on the levels of accuracy and reliability that you want.

Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[TBP]

There is no more danger in heating water with steam than there is with any other energy source. The water side of your existing electric water heater is as potentially dangerous as anything else you're dealing with. There's a short video put out by Watts in the the 1940's (so it was actually a movie, since it predated videos) that shows domestic water heaters with the pressure-temperature relief valves improperly located, plugged, etc. It's spectacular. They put some of those little tanks 400 feet in the air, others reduced shacks built for the demonstration to toothpicks. None of the heaters in this video used steam as the energy source.

 

[Joesteam]

There are many manufacturers that make prepackaged systems for domestic hot water using steam. Although you can use almost any steam pressure, I prefer to reduce the steam pressure to below the water pressure, then if you get a leak in the tubes, you cannot migrate steam into the hot water supply.
One that we like is the Constantemp made by Leslie, look at:

http://www.lesliecontrols.com/Handbooks/HeaterHandbook/HeaterHandbook.pdf

 

[EdStainless]

If you need a little more water, want good control, and you don't care about condensate recovery then talk to Pick Heaters. They build direct injection steam heating systems. This is how a lot of food products are cooked.

http://www.pickheaters.com/packaged.htm

= = = = = = = = = = = = = = = = = = = =
Corrosion, every where, all the time.
Manage it or it will manage you.

http://www.trent-tube.com/contact/Tech_Assist.cfm

 

[Joesteam]

Those injection heaters are good, however you must have 'clean' steam if you use them for domestic water.

 

[ballpeen]

O.K., this sounds very doable. But, it will be on a smaller scale than the one linked up. Its more like replacing an electric hot water heater with a steam heated one. My thinking is buying a 50 gallon tank and hook it up with a small steam regulator and a single pass line through the tank and hook it up to the condensate return.
I wasn't sure if this was done or not. It appears as though it is and on a pretty large scale as well. Is there anything commercially available thats prepacked and ready to simply hook up to your domestic steam supply thats relatively small in size?

 

[Joesteam]

What is your GPM of hot water required? What is your steam pressure?

 

[ballpeen]

Probably whatever an electric water heater would put out. Again it would only be needed for hand washing mainly so, it wouldn't require too much. Our boilers generally run at 125 p.s.i.
The way I see it, the cost to actually set one up would not be cost effective. By the time you get one running you could pay for the electricity for the electric heater for a few years.
Now if you needed a large volume of heated water, there is no question that a steam heated vessel would be economical. In fact we have such a setup there at our plant. It keeps 2- 5000 gallon tanks of water at 140 degrees F. day in day out. But this is process water and cannot be used for domestic supply.
Right now my thinking is insulation. That would get us the biggest bang for our buck. Particularly where I've read that most electric water heaters only run 3 hours, this site,

http://michaelbluejay.com/electricity/waterheaters.html

seems to explain it pretty well. And where our plant is low usage it may run even less than that. We won't know for sure until we finish our metering and get our info. collected.
Anyway I'll try to keep you guys posted as our reduction plan develops. Ballpeen.

 

[willard3]

Steam at about 50% cycle efficiency will cost $15/million btu (oil at $1.00-$1.50/gal) and elec $25/million btu assuming you do not get demand charges which will only make elec more expensive.

Oil and gas costs have spiked temporarily, but price will decrease soon.

For small amounts of hot water, capital equipment will cost about the same, elec or steam and steam capital equipment will last longer.

For domestic hot water, steam is a better paydown if your horizon is 3 yrs or more.

 

[JimCasey]

JoeSteam has it right:
The Leslie Constantemp comes in a number of sizes and will turn-down nicely. It has a feedforward integrated control system so that the outlet temperature remains constant even if the load changes. Useful for domestic hot water for washing or heating.
Pick keaters are great for making hot water for a single-pass application, such as commercial washdown spray.

 

[GenB]

For domestic water: plumbing Codes do not allow single wall tubes in the heat exchanger for hi-pressure steam systems
also direct steam as steam sparging,
There are Companies who sell the systems 50GL, they are not cheap, Most are non. Coded as 50 Gl for hot water < 250 F.
safeties include regulating PRV's, temp controllers, anti- scald valves,safety valves, relief valves (temp/pressure for the hot water side)
genb

 

[MedicineEng]

2 years ago, I replaced a gas water heater by a steam water heater for our canteen and up to now is working fine. the canteen serves around 40-60 meals per day.
I bought it from Amstrong. Make a Google search and it shouldn't be difficult for you to find their webpage.