gas fireplace - wiring question

my 10 year old gas fireplace has recently given me trouble with turning on and off. when I moved here, the house had a simple wall switch that turned the fireplace on and off. I subsequently wired an inexpensive manual thermostat in series with the switch. Thus, the switch was the master control - ON had the tstat controlling the fireplace. OFF was off ;) it has worked well for 1.5 years.....
anyway, problem with intermittent no-start. I take my first look under the fireplace and the wiring was a joke. It is some kind of braided/insulated single strand copper stuff running all over the place. a basic on/off switch in the middle with a bunch of stuff taped and jigged up....not good. I noticed that jiggling the wires from the hi-limit switch caused the fire to jump. In the end I got brave and removed much of the old, brittle wiring and am left with a bare gas valve and two wires from what I think to be a dead hi-limit switch. I removed all of the excess wire that was wrapped around the gas lines and in behind the blower for no reason....
right now I've got the pair of tstat/switch wires (from the wall) directly jumpered to the two terminals on the gas valve, and the unit works perfectly. switches on and off instantly.....having traced the wiring diagram several times, all I can see is they had the hi-limit switch and a microsswitch inline....am I missing something here?
questions:
1. the high limit switch shows continuity, yet when wired in series with the gas valve, will not allow the fire to start. huh? Should I not be able to run the high limit switch in series with one side of the tstat control wires (say the white one) and have it work? because it doesn't - yet shows continuity....and then will "sometimes" allow the fire to start.... 2. the cheep wall thermostat - shows continuity when triggered, and open when not (as you might expect). however, it will NOT turn on the fireplace. If I manually short the leads and get the fire going, it will hold the fire on and turn it off..... again, huh? it workd for over a year perfect...clearly it has failed. didn't know they failed??? 3. wiring - does any code or anything apply here (Ontario, Canada)? does there have to be a certain style or type of electrical wiring underneath the fireplace? or can I use the simple 16 awg. insulated primary wire (used in car audio) for this app? I'm using it right now for testing with no problems, but don't want to get into a code issue should a problem arise in the future....
I've tried the tstat right at the gas valve (bypassing the wiring in the wall) and it behaves the same. I'm going to get a new digital unit tomorrow, this I know....but does anybody out there have any thoughts on questions 1 and 3? My thinking is bad tstat, and bad hi limit switch mixed with crusty old wiring....
thanks! b
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Hamilton Audio wrote:

Hi, Don't forget the interlock switch on the glass front. I have two gas fire places in my house. There is interlock switch. If glass front is removed, the switch triggers preventing gas ignition. Wires are heat resistant kind. Tony (Calgary)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

there was not microswitch on the glass door, even tho the installation manual says there should be one. In reading the installation guide, I zoned in on the clearances section. 1/2" to the left and right, and 0" below the unit are allowable tolerances to combustible materials.
I've been running the fireplace now for about 3 hours continuously and the compartment below barely gets luke warm, which would confirm the 0" clearance on the bottom.
thanks for the input!
b
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I am having the similar intermittant problems with my gas fireplace. I found that the switch is bad. My system has a standard 120V wall switch connectected to the low voltage wiring system. I don't know why but the switch does not seem to last very long. My guess is that there is more carbon build up from the different characteristics of the low voltage. Maybe larger arcing when the switch is thrown on or off? Doesn't your T-stat have an off position that you can use instead of the series switch? Kevin

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I've replaced the old swing-type (mercury tilt) tstat with a brand new digitally driven piece. It does have heat/off/cool settings on it, and they work properly. However, there is a dual switch panel right at the doorway into the rec room - one for the lights and one for the fireplace. its just so easy to make sure both are off with the swat of the hand....
I've not had any problems whatsoever with the wall switch. In fact, the total series resistance of the low voltage trigger wires and the switch together is less than 1 ohm over the total run. The bad tstat, however, was over 7 ohms ;)
bmoney
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I fixed one of these things that had a bad switch too. Luckily the switch was DPST so I could just move the wires over to the other side. Ringing out the switch won't help if it's intermittant unless you get lucky and catch it acting up....good luck, Ross
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Well its obvious. I've replaced the tstat with a new digital piece, and have directly wired the low-voltage control wires right to the gas valve (no high limit switch or anything else) and it is operating flawlessly. MUCH better than before, cycling properly to maintain 70 deg, etc. Very happy with it.
My last issue is now a matter of sourcing parts - its a GTI unit (heat n glow) but in speaking with their tech line today, they can't seem to find record of the model number I have :( Also, the plate with the serial number has been painted over black, so I can't read it. Grrr.
Phoning to local dealers, there are many types of high limit switches, all of which are denoted by their cutout and cut-in temps, neither of which I can determine because the part number I have for it doesn't seem to exist with the mfg. Clearly its a safety device I want functioning.....but I get the feeling its going to be a pain....
bmoney
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.