A frugal sauna

Jan 05, 2006 24 Replies

Vot to do with 100 watt bulbs after replacing with CFs?



Maybe a sauna, with a power strip with bulb-to-prong converters and Herbach and Rademan (800) 848-8001

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$2.95 TM92HVC2293 thermostat and a small vent fan and a humidistat and a few more unswitched bulbs for reading the Sunday paper...



A 4'x4'x8' room with a small window and 15 cfm of airflow has a thermal conductance of about 15+144ft^2/Rv, and the ASHRAE HOF says a warm radiant barrier with e = 0.05 and a large air space has a thermal resistance of about US R3. With "R6.5" 1" double-foil polyiso board walls, (R12.5, counting foils), the room would have a conductance of 15+144/12.5 = 26.5 Btu/h-F, so we could keep it 150 F in a 70 F room with (150-70)26.5 = 2120 Btu/h, ie 621 watts, eg 70 watts from 1 person plus 551 from 6 100W bulbs.



If a person at rest in a 70 F room makes 155 Btu/h of latent heat, ie evaporates 0.155 lb/h of water, and 15 cfm of fresh air (an ASHRAE spec) flows through the room and the humidity ratio outside the room wo = 0.00787 pounds of water vapor per pound of dry air (70 F at 50% RH) and 1 ft^3 of air weighs 0.075 lb, 60x15x0.075(wo-wi) = 0.155 lb/h makes wi = 0.0102, with a vapor pressure Pi = 29.921/(1+0.62198/wi) = 0.481 "Hg inside the room.



At 150 F and 100% RH, P150 = e^(17.863-9621/(150+460)) = 8.09 "Hg, with a Clausius-Clapeyron approximation, and Pi/P150 = 0.06, so we might turn on a 50 cfm fan if the room RH ever rises to 6%. (With no extra moisture, it would be 100x0.374/8.09 = 0.046, ie 4.6%.) I wouldn't hesitate to turn on the fan at a higher RH, since people can safely sweat up to 4 lb/h, and with more humidity, the room will feel equally hot at a lower air temp with less heating energy. At 30% RH, the ASHRAE 55-2004 comfort standard predicts that we can lower the air temp to 142.3 F... 50% allows a 136.3 F air temp.



Nick



I am imagining sitting in a broom closet together with six 100W lightbulbs. "Blinding" is the word that comes to mind.

Good point, but I wouldn't worry about your eyes just yet. Code wouldn't allow the foam without a fire-resistive barrier covering, code wouldn't allow exposed bulbs in a closet, enclosed fixtures frequently have a 60 or 75 watt limit (much like Nick's wattage), having all of that electrical sticking out in a tight space with a lot of moisture is nuts, and the high heat would probably kill the bulbs in relatively short order.

Other than that - great idea! Sheesh.

R

Your homeowners insurance is void if you implement a violation and claim results. Read the fine print.

Never have had the city code enforcement officer come by the house and check my light bulbs for the "proper wattage"...

Guess that I will have to pull out my policy and see if I can have my 75 watt bulb in the garage.

Hot much btu in a sauna heater, my neighbors is 50a, so how many bulbs to raise it to 140f? 30-40 in short order, what is the thermostat to keep it at your temp. I think an electric heater is alot less hassle and logical, you going to replace alot of bulbs, buy alot of high temp sockets. Overall another goofball idea from you # 126.

140 would be a pretty cool sauna. 210-220 F is about what you want. And, no, you won't boil.

Commodore Joe Redcloud©

126? That number seems way high since this year is so young, low for last year, and off by at least an order of magnitude for lifetime posting.

You mentioned a sauna and boils - bleccch! I just lost my appetite for lunch. ;)

R

Have you ever had them come over to check if you have twelve extension cords running off of a single receptacle? Or a window air conditoner running off a 50' 14 ga cord? It's up to you to protect your home and your kith and kin. I pointed out the code problems with Nick's idea in case anyone was caught up in his flight of fancy.

Tip to Nick: give the bulbs to someone who still uses them.

R

RicodJour looks for problems instead of solutions:

Polyiso foam is fine up to about 350 F.

Perfectly safe in a sauna. Picture a board on the floor with an outlet strip and some bulbs in plug sockets and a thermostat in a wire cage. A space heater with a fan would be simpler but less heat-tolerant.

What moisture?

Bulbs in series or long life bulbs.

Thanks :-)

Nick

snipped-for-privacy@webtv.net (m Ransley) errs again:

Depends on how long you run it. You might enjoy learning the difference between power and energy.

This is not your neighbor's sauna.

Op cit. Keep up!

That $2.95 thermostat goes up to 260 F. This low-thermal mass sauna should heat up quickly.

Nick

More like pointing out the obvious to the clueless.

I will address the technical stuff in a minute, but answer one question. Who would find it comfortable to sit in an aluminum foil box

4 feet square with six 100 watt bulbs for heating "and a few more unswitched bulbs for reading the Sunday paper." ? I'm sure the neighbors would be beating down the doors for the opportunity to sit in the death box.

Paper is fine up to 451 F. What's your point? Any foam product built into the structure must be covered with a fire-resistive covering such as drywall. Read your code.

An exposed bulb is not perfectly safe and is prohibited by code. This from Steamist Sauna's installation instructions (pretty standard fare and they're probably the largest manufacturer in the business in the US): "Lights- Should be a vapor proof, wall mount type, with rough-in box mounted flush with inside wall paneling. The light should mount no lower than 72" above the finished floor. Do not mount the light directly above the sauna heater or benches. Light bulb should not exceed 75 watts."

Check any sauna company's specs - they all specify a sealed light fixture for a reason. Also, notice that wattage limitation? I mentioned that in my previous post. Has to do with the sealed fixture. Check the fixture above your shower - it will have the same limitation.

If your glasses are fogged from the steam, pick up the phone and call these specialists in sauna and steamrooms for verification:

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They have a toll free number so you can be frugal.

Riiiight. People don't sweat in a sauna and they're not actually dripping wet from the sweat. You're a piece of work. Is all of your information theoretical with no real world experience? Comic book conventions don't count.

To jog your addled: "Vot to do with 100 watt bulbs after replacing with CFs?" I thought you wanted to use the surplus bulbs. You're recommending that standard, relatively short-lived bulbs be used for heating instead of a long-lived dedicated heater that would have none of your inane idea's problems. And you're disregarding the numerous code and safety violations that are being pointed out to you. There's being convinced, there's being stubborn and then there's being stupid. You're being stupid. In a nutshell:

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Welcome, Dick.

R

People who like Frank Gehry? It's non-traditional, albeit 8' tall.

We doan need no steenkeeng code.

Nick

No. Gehry can design himself out of a box, and you're building yourself into one.

I honestly commend you on your attempt to recycle retired but functional items. Unfortunately, this particular idea of yours is without merit.

For someone who is constantly touting numbers, which are usually considered to be facts (unless they're your numbers and then it's up for grabs), you have a particularly weasely way of avoiding written and numerical facts when presented by others. I'd hazard a guess why, but that would mean I'd have to get into your head, and that's probably not safe, as it seems that it's a little crowded in there with all of the voices spitting out numbers.

Do try to come up with stuff that would work, please.

R

message

just yet. Code

barrier covering, code

enclosed fixtures frequently

wattage),

come by the house and check

twelve extension

window air conditoner

protect your home and

with Nick's idea in

uses them.

It's all fun until the Fire Marshall finds you operating non-hazardous location equipment in a hazardous location and causing a fire.

message

com...

eyes

fire-resistive

have

problems

100w? dunno. i saved all my regular bulbs when i switched to use in a couple areas that have motion detectors, my garage door opener, and a work lamp.

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