Replies

1. 
   DaveRicheson | Jan 23, 2004 01:50pm | #1

   Fan blade on backwards?

   Dave

1. 
   RJT | Jan 24, 2004 05:06am | #2

   untouched fresh from the factory. no nothing is onbackwards

1. 
   DaveRicheson | Jan 24, 2004 03:14pm | #3

   Which end is exhausting?

   When you say hot dawg heater I am assuming something like a torpedo heater. Correct me if I am wrong.

    Most heaters, including electric, pull air in and over the fan motor, then across  the heat source. So, if you have air blowing from both ends of a tube type heater,I am a little confused. If you are exhausting over the fan motor, something is backwards, either the fan blade or the motor direction.

   If it is new,I would take the dawg back for a replacement, repair, or refund.

   Dave

1. 
   Jeff | Jan 24, 2004 05:06pm | #4

   I Have a Modine Hot Dawg heater in my shop.

   This is a ceiling hung, gas fired unit, exhaust thru the roof.

   I notice that the heat from it is not blistering hot, but can't keep my hand in front of the unit too long.

   The heat coming from it depends also on how cold the air intake is.

   When the unit turns on, in a freezing shop (say 0 around here these days), the air blowing hardly feels hot at all, but when the shop warms to 50, the blowing air feels real hot.

   Not very scientific, sorry.

   Hope it helps,

   Jeff

1. 
   RJT | Jan 24, 2004 05:32pm | #5

   Jeff: are you using propane or nat gas? Yesterday with the temp about 5d the natural temp in my shop was 20d when I turned on the heater. After an hour it got close to 40d with the heater running non-stop. That doesn't seem right.

   This is the ceiling-hung heater like yours; four burners fire into tubes that coil back to the exhaust. There is a fan that blows over the coiled pipes to heat the room. there is a separate exhaust motor to pull the heat thru the pipes and out thru the exhaust. it is Honeywell controlled, nothing to fiddle with, just about impossible to install wrong as it is only intake gas and elec connections.

2. 
   DaveRicheson | Jan 24, 2004 06:09pm | #6

   After hearing the description, I understand what you are dealing with.

   I would look at the fan motor speed. If it is a single speed motor, then it is a design issue. If it it is two speed motor, you may need to use the lower speed. It sounds as if there is too much air passing over the heat exchanger chambers to get an adequate heat transfer. The other thing to look at is the fan limit switch. If it is a low temperature switch. it may be bringing on the fan to soon. This is ussually a normally open switch that closes when the heat exchanger temperature reaches a certin lower limit.

   There is also an upper limit switch (safety) that will shut the power off if the fan motor fails. This is also located in the heat exchanger. Do not confuse the two. These limit switches are generally marked L135 for the fan switch and maybe as high as L165 to 200 for the upper limit switch. There should be a wiring schematic on the heater or with it that gives the values of those swithches. The number after the L indicates the switch operating temperature. The letters NC or NO on the switches mean normally closed or normally open, indicating the position of the switch when power is supplied to the unit.

   It is tough to trouble shoot something like this over the net. Those two swithces can tell you a lot about the operating temperatures the unit is suppose to operate between. You might find a toll free number in your paper work that can put you in touch with a service rep, who is familiar your model.

   Hope this gives you a place to start.

   Dave

3. 
   RJT | Jan 25, 2004 04:48am | #7

   Dave: the manual states any dinking around with the fan voids the warranty and shortens the life of the unit. The only available adjustment is the input pressure. for this you need to know the specific gravity of the gas and a metering pressure gauge. Since there is a hot limit maybe I'll just jack up the input pressure and see if that helps. The thing I don't understand is why the exhaust is so hot and not the output.

4. 
   Jeff | Jan 25, 2004 05:09am | #8

   Hi again

   My shop gets just as cold.

   Usually takes a good 2 or 3 hours to get warm enough to work on days like that.

   Usually comfortable in an hour when temp is above 30.

   Before I added an addition, it worked better (was warm in an hour), but is too small for the larger area.

   I have another heater for the addition, but not installed yet.

   The size of mine is 35k and uses propane (LP).

   Careful on the size of unit for area as I think one size larger is proper over what they recommend.

   Also, any lack of insulation or air leaks really hurt the efficiency of unit.

   My large Garage door (16ft) is a real sore point, and leaks air real bad.

   I'm thinking of closing off the door or removing by next winter. Hardly ever use it.

   It sounds like yours is working ok.

   Hope that helps.

   Ask if you have more questions.

   Jeff

5. 
   RJT | Jan 25, 2004 09:15am | #9

   Thanks Jeff. What hurts is that I sold a beautiful Jotul wood-burner for this. My plans are to put in a wood floor on 2x4 studs and some radiant heat off a gas fired water heater.

6. 
   Jeff | Jan 25, 2004 03:29pm | #10

   I have a wood stove in my home (plus LP baseboard heat) and use up alot of scraps.

   But hate carring wood all the time.

   In the shop, I didn't want to loose floor space and didn't want an open flame so a wood stove was out for me.

   With a timer on my system, it starts to warm the shop an hour or 2 before I get in.

   Jeff

7. 
   DaveRicheson | Jan 25, 2004 06:23pm | #11

   Your exhaust should be hotter. It is the combustion gas that the power vent is sending outside.

   I looked at Modine web site, so have  know what you are dealing with now. What I don't see on the site is if the units have a sealed combustion chamber. I am guessing not, because of the roll out safety feature. It also mentions the high limit safety switch that will shut down the gas valve and unit power if the phelum temperature gets to high. It does not say anything about the fan sequence.

   Does the fan start immediately when the unit lights off?

    Does the unit have a summer switch on it that allows the fan only to run durring the summer?

   Does the LED readout allow you to scroll through diagnostic codes or steps to check systems values, or are they just idiot lights that tell you something is not right?

   What is your discharge air temperature at the louvers? I am guessing, but iy should be around 135 degrees F.  Call Modine and get that temperature.

   Just had another thought. Are all of the "exhaust tubes" clear? You could be getting pour heat transfer and higher than normal exhaust temperatures if a few of the heat exchangers tubes are stopped up. The working tubes will get way hot and burn out early if  this is the case.

   Just rambling guesses now.

   Dave

8. 
   RJT | Jan 27, 2004 07:04am | #13

   Dave: thanks for the research. The fan comes on soon after it fires.

   here's a question: is it possible there is some kind of air bubble in the pipe? like in the downtube? is bleeding the line a thing to do?

   as for your other inquiries, I hate to answer as they are technical and little over my head. I understand lobbing logs into a wood stove, but when we're getting into roll-out switches and specific gravity....... duh.

2. 
   USAnigel | Jan 25, 2004 06:33pm | #12

   May sound dumb, you did get all the packing out?

1. 
   RJT | Jan 27, 2004 07:05am | #14

   no packing.