Replies

1. 
   tedd | Nov 25, 1999 08:21am | #1

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   That's a tiny heater. But like all combustion appliances, fresh air supply to the a fire that has an exhaust vent is a good idea. Although there are lots of people who would disagree with me -- as you will soon hear. In your case, using a ventless heater does not draft out interior warm air so the need to provide a fresh supply of outside air changes in terms of not having to prevent loss of your heated air.

   The heater is so small and you spend such little time in the bathroom, why do you need fresh air ? If its to increase efficiency of the burn, I doubt you will get much benefit from an indirect vent. If its to feed fresh air to overcome the O2 loss and handle the build up of exhaust and particulate, then you need a two way -- fresh air in / stale air out approach. A bathroom fan will probably do the trick (exhaust) in combination with the infiltration around the door (intake). Attic floor vents are a no-no for a whole lot of reasons.

1. 
   Steve_Hansen | Nov 26, 1999 11:25am | #2

   *Tina,I am a big fan of ventless gas heaters for some applications. I have one in my cabin and plan on using one in my new shop. However, in the case of bathrooms that are not used very much I think resistant electric heat is a better option. You will have to run a dedicated line from your electric pannel. About the same level of difficulty as running a gas line. I agree with Tedd. The combination of a exhaust fan (couple of minutes every so often) and a couple of door openings every now and then should provide sufficient ventilation. Tell your inspector Tedd and I said so. If he does not relent then go through the wall to the study.Good luck,Steve

1. 
   TinaG_ | Nov 26, 1999 09:05pm | #3

   *Thanks Steve and Tedd. Yes, it's a small heater (it's also a small bathroom!). I have since checked mfg's installation instructions and calculations and it appears the space is large enough for the size heater not to need outside air. Steve -- electric is out of question as we are totally solar-powered and any electric heat eats up mucho energy. We use unvented (what I call a 3-bricker) in our cabin, too and it's great. Out here where we're building, we don't need any type of inspections or building permits (I guess the state figures if we burn up, we're just burning up ourselves since there's no one else within miles of us), but we had an inspector come anyway to make sure we had everything done correctly in case we ever sell this place (over my dead body!). Anyway, the inspector expressed concerns about oxygen supply -- said somone could hop in for a long shower with that little heater cranked up and be carbon-monoxide-dead before he knew what hit him. We figured inspector was being conservative. Mfg's instructions seem to have borne that out.

1. 
   Steve_Hansen | Nov 27, 1999 07:46am | #4

   *Tina, I remember now, you are the Brown Cow Gal. This is just a thought, never tried it, and don't know if it will work or not. You will be using your heater when it is cold. Cold air is heavy and will fall. Your heater needs oxygen to burn but an over supply of cold air will offset the heat and give you a negative result. It is possible a small tube, say 1/2" run from your attic to the immediate vicinity of your heater's burner will provide a sufficient supply of air. Think I will try something like it on the ventless heater in my cabin. Lot of admiration for off-grid folks. Takes a special breed. Good luck!Steve

1. 
   Bob_Walker | Nov 27, 1999 05:35pm | #5

   *TinaG:Double check on the manufacturer's instructions _and_ warnings: many ventless heaters I've lookied at specifically warn against installing in bathrooms. Also, _all_ ventless heaters I've seen instruct you to open a window in the room.If at all possible, use a CO alarm with an LED readout (although I think those require A/C) CO alarms don't sound until there has been high CO for a specified period of time (e.g, 70 ppm for 8 hours, shorter times for higher CO.)Some experts feel 70ppm is too high, particularly for infants, aged, and those with heart and respiratory problems. Repeated exposure to lower levels of CO can have significant, long term health effects.Also, take a look at the article on ventless gas heaters at http://www.jlconline.com/jlc/archive/energy/vent/BTW, the rule of thumb for air supply to combustion appliances is 1 sg. in of free vent space for every 1,000 BTU. For a 5,000 BTU heater, you'd typically want a 1 1/2 in or slightly larger air supply. Situations vary.Bob WalkerCarbon Monoxide Analyst

2. 
   Jerry | Nov 28, 1999 11:50am | #6

   *Bob,I'm not being argumentive, but this is something that concerns me. You say:b BTW, the rule of thumb for air supply to combustion appliances is 1 sg. in of free vent space for every 1,000 BTU. For a 5,000 BTU heater, you'd typically want a 1 1/2 in or slightly larger air supply. Situations vary.5,000 BTU would then require 5 sq. in. of free vent, however; a 1-1/2" vent seems too small (2.25 sq.in. if square or ~1.75 if circular). I had read somewhere that 1 sq.in./2,000BTU is sufficient making the 1-1/2" vent seem right. Comments...Jerry

3. 
   Bob_Walker | Nov 28, 1999 05:00pm | #7

   *Jerry,Hmm, I think I goofed with my math: I _think_ I did pi * d, should have been pi * rsquared, of course.Assuming 1 sg in per 1000 btu, it would need about a 2 1/2" diameter pipe.I forgot to mention, I believe some building codes require 2 air inlets, one with the inlet high in the room and 1 low. Using this formulation, & the 1:1000 ratio, you'd want two air inlets 0.9 in diameter I don't have an authoritative source citation for the 1:1000 btu figure, but I have heard it at several training sessions, both for home inspections and for HVAC carbon monoxide analysis certification courses.I wonder if your 1:2000 is assuming the 2 air inlets?I always stand ready, of course, to learn.Bob Walker

4. 
   Bob_Walker | Nov 28, 1999 05:04pm | #8

   *TinaG:Further: On the Web, I ran across a CO alarm which appears to be battery operated _and_ has an LED, it's made by AIM Air Safety Products. Sorry, I lost the URL, but you can find it through any Web search engine.Bob

5. 
   TinaG_ | Nov 28, 1999 09:36pm | #9

   *The bathroom has a ceiling vent/fan (Broan variety). Would that draw enough air into the room and through?

6. 
   Bob_Walker | Nov 29, 1999 12:25am | #10

   *I'm not sure what effect a vent will have, if any. If the heater was vented, the bath vent could be a problem, by depressurizing the room and causing the vent to back-draft, but that wouldn't appear to be an issue.It seems to me, but I'm not sure, that the bathroom vent would reduce risk of CO from the ventless heater by removing combustion gases. (Some of the stuff I've learned and am learning about venting of gas appliances seems counter-intuitive to me, which makes me reluctant to draw conclusions in areas I'm not familiar with.)Bob

7. 
   Ron_Schroeder | Nov 29, 1999 07:42pm | #11

   *TinaGIf I remember, you have a boiler for your space heat. I would run a couple of feet of baseboard heat in the bathroom.I used to have a ventless heater in my workshop. I got tired of the headaches. I now have basebord heat.What brand of boiler did you decide on?Ron

8. 
   TinaG_ | Nov 29, 1999 09:08pm | #12

   *Ron. You remember correctly, but we've decided against central heat at this time. We're using individual gas (LP) heaters, all vented except this one bathroom one. We have a large, central, freestanding "russian fireplace" from Envirotech (Dietmeyer Ward & Stroud in Washington State), that should keep us warm most of the time. The gas wall heaters (5 of them) will take the chill off certain areas if we've been away or if guests want their bedrooms warmer than we keep the house, etc. We decided central heat was overkill at this point, also more $$ than we want to spend right now. So we'll spend a few winters and see how it goes.

9. 
   Ron_Schroeder | Nov 30, 1999 01:19am | #13

   *TinaHow do you heat your water?Ron

10. 
    TinaG_ | Nov 30, 1999 07:50pm | #14

    *Ron -- gas water heater, old fashioned kind. We opted against solar hot water for time being.

11. 
    Ron_Schroeder | Nov 30, 1999 09:00pm | #15

    *Tina,You could run a baseboard section from the hot water tank. For that matter you could use the tank for backup heat for the whole house. DC circulating pumps would keep your electric use very low.Ron

12. 
    andrew_d | Dec 05, 1999 07:19am | #16

    *I've had a touch of CO poisoning and am really skeptical of the ventless heaters. That they even NEED an oxygen depletion sensor makes me wary. But for well-vented small-scale applications... you be the judge, and watch for headaches, blurred vision, loss of color vision, and other symptoms of blood poisoning. I do use on in open areas as a radiant heater and am considering one for emergencies, but only when we are awake and keeping an eye on it.To make your exhaust vent work well, you ought to allow a decent air supply into the bath. A passive louvered vent or high-low vent will not allow much noise out and will allow the fan to exhaust MUCH more effectively (and for less pow) -- plus will supply plenty of O2 for the heater and assure removal of exhaust.

13. 
    Bob_Walker | Dec 06, 1999 04:32pm | #17

    *<> Try reading the article on them at the JLC site: http://www.jlconline.com/jlc/archive/energy/vent/ Talk about "wary"<> At least some of the ventless heaters have a printed warning NOT to use in bathrooms.<>I wouldn't rely on symptoms as an detection device: there is mounting evidence that chronic, long term exporsure to low levels of CO can cause significant, debilitationg health problems. (I don't know if the victims in such cases didn't show some symptoms, but why take a chance?)A comprehensive site on CO is the Carbon Monoxide Headquarters at http://www.phymac.med.wayne.edu/FacultyProfile/penney/COHQ/co1.htmBob WalkerCarbon Monoxide AnalystNW Ohio

2. 
   TinaG_ | Jan 04, 2000 11:55pm | #18

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   Will be installing a small (5m btu/one-brick) ventless LP heater in an interior bathroom. Besides including a carbon monoxide alarm, would like to provide a vent somewhere to bring in air. Don't want to put a grill on bathroom door, as that would negate sound-proofing. Would one or two ceiling vents into vented attic work? Next best idea is through wall into a small study area. Don't want to go through floor to crawl space because all that cold air would negate the little heater's warmth. Our inspector said that space under bathroom door wouldn't bring in enough air. Any suggestions out there?