Question for you HVAC guys

[Bill Stockard]

I have a Dayton Model 3E241 100,000 BTU LP fired Unit Heater in my "toy house". It has a Honeywell Model VR8200A 2082 Combination Dual Gas Thermostat Controlled Valve. The heater has been in use for 10 winters and had about 300 gallons of propane run through it.



The problem I'm having is keeping the standing pilot lighted. The flame seems too low and barely heats the thermocouple enough to keep the control valve from shutting down. I have cleaned the pilot line and gas orifice with Spray Brake Cleaner in the line and blown it out with compressed air. That seemed to help a little bit. I haven't checked the gas pressure, but I have changed the regulator at the storage tank and checked the drip line for oil--none present. The burner runs fine when it lights. Is there an adjustment on the control valve to adjust the size of the pilot flame?



The pilot will stay lighted for a couple of weeks and then for no apparent reason, it goes out. The main burner isn’t blowing it out because it will shut down when the main burner doesn't operate. The heater is 10 feet above the floor and not subject to drafts.



Any advice would be appreciated.



TIA,



Bill

 

[HeberRam]

over the hill...

Face it Bill that thing is 10yrs. or more old. Do you still have the old "flame"?



Try changing the thermocouple.

 

[chuck3]

Thermocouple.

I'm with Heber, on the thermocouple.

 

[Bill Stockard]

"old flame"

Thanks for the replies.



Yep, my old flame is gone, but the heater did have a larger pilot flame. There's no adjustment?



I agree that the thermocouple is probably getting weak; however, it only burns about 4-5 months per year. Our winters don't last very long.



Thanks again,



Bill

 

[maint.man]

What can some times happen with LP is the orifice can become coated inside with deposits from the LP gas. The only way to really clean it is with a bit made for that purpose, and rotated by hand. Also what are you using for gas line ? Just curious beacause copper can ,after years of use , become a problem .

Hope ya' get er' straightened out .

Brent

 

[C Schomer]

TCs are cheap, try that anyway. The flame should be big enough to hit about 3/8" of the TC tip. Look at the gas valve around the area where the pilot line connects. Most of them have a screw or cap that covers the pilot needle valve screw. If it has the needle valve, they can get restricted with crud. Open the needle valve if it has one and see if the pilot flame gets bigger. The pressure may be low if you can't get the pilot flame strong enough. Pressure should be 10-11"WC. If you have a good pilot flame and new TC and it still drops out, the magnetic safety valve is getting weak - a little unusual with Honeywell valves. That is a combination valve and is also 100% shutoff - all flow stops if pilot flame goes out - an absolute MUST with LP. If you have to get a new one, make sure it is 100% shutoff, has high enough btu rating for the furnace, correct control voltage and is for LP or convertible for LP(LP valves don't use a regulator). Parts, like the operator and magnetic safety are available but the whole valve is usually cheaper and is readily available. If that's a 24 volt valve and you change it, you may have to adjust the heat anticipator to match the new valve. The pilot orifice is probably . 010-. 012". I've had to drill them bigger to get a better flame but that shouldn't be necessary after you've cleaned it and it's worked for ten years. Craig

 

[DRR-24V]

Try A Tip Cleaner

Bill, I'll bet that tip is coated inside. Try a Welding/Cutting Torch tip cleaner and see if the flame goes back to what it used to be.

 

[illflem]

Had the same problem with a boiler this summer, welding tip cleaner fixed it right up. If the heater was working correctly before I highly doubt if any pressure regulator settings have changed.

 

[Bill Stockard]

Thanks for all the replies. You guys are great!!



I have a tip cleaner and will try that first. I thought that might be the problem and thats why I tried the Brake Cleaner and compressed air. There is a needle valve on the control valve under a cover screw right near the pilot outlet line connection. I've tried adjusting this and don't get any change. This leads me to believe that the pilot orifice is partially plugged or that the needle valve doesn't have anything to do with the pilot flame.



Also I'll get a thermocouple. If that doesn't work I'll go after the control valve.



There's cold weather in the forecast for this weekend and early next week and I want the heater to be dependable. I keep the thermostat on 45 degrees and so far this fall it hasn't needed to run yet. Gotta keep the toys from freezing!!



I'll let you know what I find.



Thanks again,

Bill

 

[C Schomer]

The pilot works off of full inlet pressure on small gas appliances - not regulated like the main gas to the manifold. The neddle valve will control the pilot if you turn it in far enough. 99. 99% of the time the needle valve is not necessary to turn the pilot down. You don't see regulated pilots til you get into larger power burners. Be careful cleaning the orifice with anything other than the correct size orifice drill. If you hog it out a few thousanths with something too big, you'll be needing that needle valve for sure. Then you could end up with an orange flame that soots. It's a combo of orifice size/gas pressure that controls the air/fuel ratio on those things. I have a small wire brush(the size of a toothbrush)with very fine bristles. They are small enough to clean out the tiny propane pilot orifices. I use that in a pinch when I don't have my orifice drills with me. You can buy the brush at a hardware store. Craig

 

[Bill Stockard]

I cleaned the pilot orifice with a welding tip cleaner being careful not to "ream" the orifice out any larger. The flame is a little higher. Also I tried opening the needle valve on the control valve which seems to have little affect on the flame height.



I was wondering about the sticky goop that forms on propane appliance valves after a period of use. The next time I have the pilot supply line off the control valve I'll clean the needle valve part of it out.



I'll pick up a new thermocouple after the holidays. Also, I'll check with my propane supplier and get them to check the pressure with their manometer.



It was 22 degrees outside this morning and the temperature inside the toy house was a "cozy 46" which is where the tnermostat is set. Everything seems to be working fine. I'll give it a few days and see what happens. So far, so good.



Thanks for the suggestions.



Bill

 

[HVAC]

Tedious Job

Bill, guess your going to have to lay down the BIG BUCKS to have a service person come out and unravel this mystery for you $$$$$$ I'm a little far away or I'd help



It sounds like you have correctly identified the pilot flame adjustment although it does not seem to be of any benefit. All you can do is to progress down the pilot gas route to find the restriction.



You mentioned the problem seems to be intermittant. Someone mentioned the problem with using copper tubing to deliver the fuel to the appliances. The copper reacts to the LP and you get a sort of scale on the inside. This can plug things up. For instance, you might check the screen on the inlet of the gas control for the heater. The pigtail/hogtail curly connector from the tank service valve to the regulator on the fuel delivery system is copper and can also plug. Are their other appliance on the same system, are they running properly?



Like what was mentioned before, normally the problem is the pilot orifice. They get dirty and need to be cleared. Sometimes it's as simple as sticking the nose of a vacume cleaner hose over the pilot burner. More frequently it's necessary to disassemble the pilot burner and dig the orifice out. Hold it up to the light and see if the hole is visible. It is only about . 009. Use a brush or something soft to attack it with. You don't want to increase the size of the orifice accidently by sticking an awl in their! The coolest serviceman tool for this is called a broach. It's sort of a triangular needle. Insert into the orifice, apply a quarter turn and your done! It can be used to increase the size of the orifice if necesssary. It helps to have good eyes for this!



OK, you've cleared the orifice. Blow through the tube to the pilot orifice orifice. Is is clear? With the tube disconnected from the gas control, push the button to light the pilot and see if you are getting an adequate volume of fuel out of the control. If you have had the furnace in service for 10 years it would be a good idea to put a manometer on the fuel supply system. You should have 11"-14"wc to the gas control on the furnace.

Fifteen years is considered the useable lifespan of a regulater and your two thirds there.

 

[C Schomer]

It's the hydrogen sulfide that copper doesn't like. Copper is usually ok for LP. It wouldn't hurt to check it like HVAC said! There will be a thin gray crust inside the copper that flakes off easily when disturbed, if you have that problem. The flakes can plug everything. You can make a quicky u-tube with clear tygon tubing. Just double back about two feet and tape it together - fill with water half way(or half empty, if you're a pessimist). That M/H valve should have an 1/8" pipe plug right beside the outlet - takes a 3/16" allen, I think. Take it out(not when the main flame is on), put in a barbed fitting and connect the u-tube. Make sure you have the water in the u-tube, so gas doesn't blow thru it. Make sure none of the test fittings leak for this manifold pressure test! Light the furnace and check WC"(measure between the tops of the water columns in the tube) with the main flame on and watch the pilot flame at this time. Pressure should stay up around 10" and the pilot flame still has to hit the end of the TC good. This is the best test when in doubt about pressure - and if pressure is causing your problem. A little lower pressure doesn't hurt but will under fire the main burner and you will loose some heating capacity. Turn on any other appliances on that gas line to be sure the line can support everything - check WC" and pilot again. If something is restricted, this will show it for sure. This is where 'the rubber meets the road' for your pilots and gas distribution system. MANY times the pilot drops out during main fire due to pressure droop. If your pressure is low, you can turn the reg in a little. Check pressure with everything lit AND with everything off(pressure droop test) to be sure the pressure isn't going too high on the off cycle. You can wind up with too much pressure and have pilots blow themselves out when the main flame is off- velocity of the air/fuel mixture is greater than flame propagation rate. Craig