CO Problem?

[OlJarhead]

- Fresh air intake: The room in which the heater is located must have an air inlet not
less than .75 square feet (roughly 9" x 12" or larger).

That is from Marey.

PRECAUTIONS:
1. The water heater must be installed in a well-ventilated area. An exhaust pipe of
double walled steel for Class 3 appliances (located at most home improvement
stores in the water heater section) must be installed to discharge the exhaust from
the flame. During operation, the water heater consumes a lot of oxygen, so the
exhaust pipe and outlet hole must be properly installed. Refer to exhaust pipe
section for details.
- Failure to properly install the room intake and exhaust pipe will cause
oxygen depletion in the area around the water heater, which can cause
incomplete combustion. Carbon monoxide poisoning, death and serious
accidents can occur due to incomplete combustion. ALL USERS OF GAS
APPLIANCES OF ANY TYPE SHOULD EMPLOY THE USE OF A CARBON
MONOXIDE DETECTOR.

So, they spelled it out, I ignored it (not completely).

The problem I had with this is that they wanted me to have a 9x12 inch opening into the outside world INSIDE my cabin I've worked so warn hard to make warm and cozy.  I installed the hot water heater on the outside of the cabin but didn't want to put such a large vent to the outside world as it completely defeats the purpose of installing inside all together -- let's face it, below freezing weather with 9x12 inlet means frozen pipes and a useless heater in the winter.

Where am I going wrong here?

Perhaps I can install the trickle vents provided I use at least two of them?

[Jeff922]

Trickle Vent is intriguing.  Seems like it would do the trick.

[OlJarhead]

Trickle Vent is intriguing.  Seems like it would do the trick.

Only thing is, and I just did the calcs, it's 1.77CFM per vent.  Theoretically that would be 3.54 CFM with two of them but is that really enough for an instant on hot water heater?  That I don't know.

[OlJarhead]

http://www.dr-fix-it.com/hvacduct.html
This shows a 9x12 vent flowing 1750cfm which seems an awful lot for this heater considering I've read that woodstoves draw about 350cfm.

[MountainDon]

OJH.... after installing the stove fresh air system I would most likely call it good for now and see what happens. If the detector detects any CO in the future I'd try to figure out why and then see what to do. I'd do that before installing a passive or an active air exchanger. That is as long as there are no other issues such as high humidity and condensation on windows.


The rule for sizing rooms vs gas appliance use is 50 cu ft of room air per thousand BTU. This link has info. If the interior space is too small then exterior venting is required. It's Nevada specific and is based on the UMC (another one of those codes that help us figure things out; there is generally a code for just about anythng we can shake a stick at    )  and though old the numbers are the same for NM so probably a good guide for all.

[MountainDon]

Further info on gas appliances and combustion air
http://staff.jccc.edu/jbennett/current/Fall%20Classes/Heating/COMBUST.htm


My water heater install directions notes:  1 square inch of free vent area per 4000 BTU/hour rating for vertical ducts and 1 sq in per 2000 BTU/hr for horizontal ducts. Same info on the new furnace.


I now recall that was another factor involved with the decision to not get an on demand whole house water heater several years ago. Not only did we need new gas piping to cover the higher volume for the burner but the venting needed changing too (heater in center of house meant a fair amount of disruption.

[Carla_M]

Only thing is, and I just did the calcs, it's 1.77CFM per vent.  Theoretically that would be 3.54 CFM with two of them but is that really enough for an instant on hot water heater?  That I don't know.

If one was an inlet and the other an exit it would only be 1.77 wouldn't it?  You need 4, two pair for 3.54.

[OlJarhead]

If one was an inlet and the other an exit it would only be 1.77 wouldn't it?  You need 4, two pair for 3.54.

I was thinking that when the heater was lit it would draw from both since they are not restricted.  Thus two can be 3.54cfm intake as long as that much is being drawn out through the heater stack.

[OlJarhead]

OJH.... after installing the stove fresh air system I would most likely call it good for now and see what happens. If the detector detects any CO in the future I'd try to figure out why and then see what to do. I'd do that before installing a passive or an active air exchanger. That is as long as there are no other issues such as high humidity and condensation on windows.


The rule for sizing rooms vs gas appliance use is 50 cu ft of room air per thousand BTU. This link has info. If the interior space is too small then exterior venting is required. It's Nevada specific and is based on the UMC (another one of those codes that help us figure things out; there is generally a code for just about anythng we can shake a stick at    )  and though old the numbers are the same for NM so probably a good guide for all.

The thing is, the woodstove wasn't actually being used when the alarm went off.  Only the cook stove and the heater.

[MountainDon]

   well then something was not burning efficiently and making a good amount of CO. Reason would have to be either an appliance not "tuned" for the altitude or insufficient air supply if everything was properly tuned for the altitude. That is assuming no restrictions to the burner or chimney flue.  The issue I had was spider webs in the flue. That was the same thing that nearly killed our neighbors a few years back. The burner)s) had the proper size orifice for the altitude, but there was a restriction. You would think the flame of the pilot or burner would be enough to burn spider webs away fully, but it can be enough of a problem to snuff you.

You mentioned being pink or red cheeked or faced. That is a very bad sign. More often seen in the deceased than the living IIRC. CO is used to make meat appear more red to the consumer. Hope you figure out the cause and the cure. Everything running well should not produce CO like that.

[Jeff922]

Also OJH, are you sure the proper orifices are installed for LP?  Which is to say, are you sure the proper conversions were done?   In addition to that, what about the gas pressure?  I know tankless units require the pressure to be in a certain range or they just won't work properly.  You could have your gas company come out and do a manometer reading at the regulator and at the heater itself.  I think this is a fairly common problem.

[MountainDon]

pressure check may be a good idea. OJH's cabin is rather remote so not likely a serviceman is a cheap deal. There are LP gas manometers, simple ones with a tube, that can be foind on amazon for maybe $30 or so.

[OlJarhead]

The heater is specifically LP so that shouldn't be an issue but I don't know if running it at 3200 feet makes a difference 

No way to get someone to come out without spending a fortune! lol

I'm using an old BBQ regulator which is supposed to be in the right range,.

[Jeff922]

I think Don has the right idea.  Pick up a manometer and just eliminate that variable (you can always ebay it when you're done).

[MountainDon]

old BBQ regulator

Ah-ha!!  Well maybe.

A grill regulator is a simple one stage regulator. A typical propane installation from a large ground mount tank uses a set of two regulators; a high pressure and a ow pressure. The high pressure reg drops the tank pressure to about 10 psi. It is mounted at the tank. The low pressure regulator is mounted at the house or close to it. The low pressure reg drops the pressure to 11 inches of water.

Single stage regs are not as precise as separate high and low stage regs. Appliances such as ranges, furnaces and water heaters require more precise pressure and supply regulation than a BBQ grill or small space heater. The single stage regulator may be the source of the problem. A good two stage regulator such as found for RV use can be used in place of the separate high and low pressure regulators (as long as the cabin/home is not being inspected and as long as the propane comes in portable cylinders, 20 to 100 lbs.

That's a maybe, not a guaranteed solution, but one that holds great promise.

[MountainDon]

Good regulators are quite dependable. One reason a regular home propane system uses two individual regulators is for safety. If a regulator diaphram fails \the regulator will pass the inlet side pressure through to the output side. With a system of two separate regulators if the low pressure regulator fails it will pass 10 psi; more than what is needed but not overly dangerous. Appliances will usually blow themselves out. If a single stage regulator diaphram fails the full tank pressure is passed to the inside of the bldg.  I am not certain what happens if the high pressure reg diaphram fails in a two reg system (hi-lo)

[OlJarhead]

Good info, thanks Don!

We have two 20 gallon tanks (100lb) that we want to use and planned on getting a regulator to fit them (not the same ACME style as the BBQ tank) so that might help.  I have been meaning to head to a propane place to get that done.  Seems like it's time.

Also, on a side note, the stove has a built in regulator but still requires the .5psi (I believe that's right) regulator on the tank.

[MountainDon]

stove/range regulators want to see 11 inches water column coming in. They refine that to the precise pressure required for reliable operation.

We have used the RV two stage regulators with only one problem in many many years. Starting with the RV for 20+ years and then in the cabin. They are less cash than the "real" system of hi and lo regs. I've never been worried about them, though I do have a spare for just in case on some cold winter day.  I bought mine online through http://www.pplmotorhomes.com/parts/lp-gas/changeover-lp-regulator.htm

The spare is mounted with all hoses and piping using a union fitting for quick detach and swapping. Hope to never need it but...  (years ago we had one fail on the RV at a very inconvenient time and location ... once burned, twice shy...) 

[MountainDon]

I forgot to mention there may also be a small chance that the regulator might not be able to deliver the required volume of propane the appliances were asking for. Especially if the weather was cold and the tanks close to empty or smaller than 100 pounds.

[Jeff922]

I'm probably stating the obvious here but for the proper volume you have to have your lines sized properly too.  I ran 3/4" black-pipe directly to my tankless heater as required by the manufacturer (Takagi TKjr-2 which is a small one).