Jump to content
I Forge Iron

JLP Blacksmith Teaching Center.

Recommended Posts

  • Replies 966
  • Created
  • Last Reply

Top Posters In This Topic

Runs great..   Keeps the shop about 60F even with the tarp wide open at the top.  Pretty even heat too.. I'm actually pleasantly surprised. 

I have to setup so the blower fan comes on at about 50f and will run till 180F then the burner shuts off till about 120F and then comes back on..  This is new just Thursday as I installed a new Limit switch which controls the fan. 

I put an hour meter on it for run time on a full tank of fuel and right now it's at 30hrs.. 

With it outside it does cool off the air some entering and it takes a while for the fan switch to kick off the burner on the colder days.  (there are 3 speeds for the fan so can swap wires on the motor to get less or more flow).. there are 3 wires on it so I'm guessing that the 2 position relay is controlled by the thermostat. 

If I ran a cold air duct back into the building it would work a little more efficiently as then it would be using warm air vs 20F air that has to be warmed up.. 

Overall it's a success..  I ordered some back up parts and a dual hour meter so I can keep track of burner on time and total run time. 

I imagine at this point on the full tank it's somewhere in the 40hr range on run time..  I haven't kept track as I have just been turning it on and letting it run while I do other things..  Once the thermostat gets here I'll leave it on overnight which will be helpful. 




There are a couple of things going on which I don't quite understand as I am not a furnace/sheet metal guy.. 

There is a ratio for the plenum to have that has something to do with having the right amount of back pressure and a solid wall for it to smack into. 

I've read about it some but can't seem to put the information together in usable form..   

I believe now that I have to change the design of the discharge taper I made and make a straight sided box with a  solid wall in the middle with a gap the size of which was original in the metal duct which is like 21"X 9"..  This area is what is needed for the correct back pressure I believe.  So 2 sections 10.5X9" open on either side should give me  the mixing and then taper it down.. 

Sadly the ducting I ordered was completely out of stock so just have the heater shoved under the tarp with a huge gap underneath. 

So, now thinking of moving it into the shop and just angling the exhaust pipe out the top..  Nice thing is the double wall pipe does not get hot enough to melt the tarp so thats good. 

The front shroud that covers the fan is not tall enough so there is to much turbulance or shock wave at the blower motor. 

I need to put a bump in to allow more clearance..  I was thinking a truncated cone that way I can fit a duct when it does come in. but will also be usable with the cover down in the mean time.. 

The new brain box works great. It's fun seeing all the functions and diagnostics.

 Not sure where the red limit wire goes to on the brain box itself but for the time being I have it connected to the hot wire and it works..  I'll call Honeywell tech support and find out once the thermostat arrives.. 

It's been a learning curve for sure..    I know a bunch about oil fired furnaces now. 

Link to comment
Share on other sites

I contacted Olsen directly and got the correct wiring and manual for the furnace..  The wiring in the manual I had posted originally was wrong. 

28886_R2, 06-01-03, HMLB-WMLA Installation Instructions (1).pdf

On another note the electric company showed up and got 2 poles in.. 

Now lets see when they come back to do the 3rd pole and install the transformer. 


Link to comment
Share on other sites

Oh, 1 other thing..  

Knowing what I know now, I would have looked for a low boy unit.. 

and also knowing what I know now there was no real reason to cut all the sheet metal off. 

I cut it all off because I was going to change the design of the furnace completely.  I was going to mount the burner at what used to be where the blower is, and move the blower up to the top of the unit. 

This unit has a ceramic liner in it which glows red after a heat cycle so evens out the heat some.. 

I did not know this when I bought the unit..  My plan was to cut open the end and put a flame deflector in to spread the flames out to the side walls..  But after seeing the liner inside and there is no good way to get it out. 

I decided to leave it basically as it was.. 

so could have used all  the sheet metal left in place with all the doors and such and would have sealed up the unit against water and weather very well.. 

it would have been wider but I only really gained about 7" narrower. 

Link to comment
Share on other sites

Be sure and update your owners manual on the furnace. (grin)

You will end up getting the furnace running well just in time for spring and warm weather.  Not to worry, it will be ready for the frosty fall mornings.

Link to comment
Share on other sites

there is no information as to make sense to duct work in the manuals.. Not without doing all the math.. 

I did go and look at other furnaces in this size range and they do have charts for duct work.. 

My measurements above were correct.. So my guesstimate was good based on what was there. 

I had to call Olsen to get the right manual..  The one of their website is wrong for this vintage..  In some ways this is a much simpler unit..  It uses just a few relays and switches to serve all the functions vs a control board with electronic circuits. 

Glenn, once I am done I will update a booklet with wiring in it to show what has been changed. 

So far I have only used 1 different colored wire..  Otherwise it's all pretty straight forwards.. 

In the literature there is no mention of the Limit wire for the burner control box (aka brain box) in the controller instructions nor in the Furnace wiring schematics.    I'm not familiar enough to know where it goes so it would just be a guess. 

I'll call Honeywell monday to find out.. 

By the way.   I have never in all my life found such good owner manuals and service manuals as I have found on the MFG's websites..  

The information is feature rich and it's all there for free.. Amazing really. 

Link to comment
Share on other sites

On your earlier photo the nameplate indicated the unit pushes 0.5" WG of external static pressure  (ESP). This info should help you size your duct.  Just recall that the inlet filter must be accomodated as well. Most supply duct is sized based on a friction loss of 0.1" loss per 100' of duct length.  This will allow you to figure your minimum duct crossection for each airflow on any duct branches you install.  If you plan on an inlet filter you likely have around 0.3" of static left for overcoming duct friction.  This should allow around 300 equivalent linear feet of properly sized duct.  Equivalent feet because each 90 degree elbow can be between 30 and 50 equivalent feet depending on configuration. 

I can help you with your duct design if you need more information. 

Link to comment
Share on other sites

I looked at the cfm and 1050 for this sized heater is what kept coming up.

The chart I looked at had the same opening size as the original duct work.  So just assumed.  

There is no air mixing in the taper section now so there is a cold boundary layer around 1/2 the bottom heat exchanger. 

Turning it from upright to on its side changed the flow pattern of the hot flame and both ports are now horizontal vs vertical so the burner gases stay towards the top of the unit.


I was originally going to change the configuration to down draft and this would have solved the problem.


This really is a learning time for future developments. 

The motor is  3 speed and connected to 2 speeds at the same time. The volume of air based on speed of the motor and stack temperature of between 300 and 400F.


690-1500cfm is what it states in the manual.



Link to comment
Share on other sites

At least I am qualified to help a bit with the heater problem...  No way I could teach Jen about smithing.


Backpressure is usually not required for the supply duct from a furnace that heats indirectly (with a heat exchanger) because the critical parameter is to avoid having too little airflow and overheat the material of the heat exchanger.  Thermal shock can also be a problem, but less often. 

The outlet of a furnace is often smaller than the ideal supply distribution duct, while the inlet size of the furnace is typically closer to ideal or a size or two larger (to accommodate the ideal air speed for the filter that is usually located there). If I were designing the distribution duct from your furnace at 1050 CFM and an ESP of 0.5" WG I would likely use a supply duct with one of the following crossections: 18 x 10, 14 x 12, or 14" round duct.  I would stick with a return duct that was a little larger (I like to use 0.08"/100' for returns, so 18 x 12, 14 x 14 or 16" round.  As I noted earlier you can have a maximum duct length of around three to four hundred equivalent feet, total for both the supply and return.  Depending on how your furnace fan is controlled, less duct friction will allow more airflow through the furnace, which will just keep the heat exchanger cooler, but too much (or too small) duct will result in restricting airflow and potentially overheating the heat exchanger.  Remember that duct elbows add around 30' of length, depending on their configuration, and a plenum box with a side outlet can do the same.

Link to comment
Share on other sites

Arkie, No, no.. It's all good.    The heater was part of my overall plan..  Huge learning curve and have been interested in oil burners for years..  Just never had a reason to invest the time into them to learn about them.. 

The overall goal is to understand them enough to see about not only waste oil furnaces but forges. I've learned so much.. 

Ideally it's part of the overall plan... :) 



Link to comment
Share on other sites

3 hours ago, Latticino said:

At least I am qualified to help a bit with the heater problem...  No way I could teach Jen about smithing.

This Latticino fellow sounds like a useful guy to know. You can tell because he uses terms like "backpressure" and "duct friction" but not in the form of a question, i.e. "What in all that's sacred is backpressure?" or "Do ducts have more or less friction when they quack?"

This has really been an interesting build to follow---thanks, jlp. Are you still on schedule for a grand opening? Should I get a beverage ready for toasting? Truthfully, I'm getting a beverage ready, regardless, but congrats on your continuing progress.

Link to comment
Share on other sites

Latticino,  Everyone has something to teach others.. Even masters learn from students.. It's part of the whole process.. Not getting bogged down simply in what one knows but also looking at others for what they might bring to the table.. 

I've learned a bunch about forging from people who have just started as well as old timers..  Funny where the little kernels come from.. :) 

While I don't use it, in a round about way  I learned something from you..  JHCC had mentioned about spending time with you making a hawk and you guys used salt to tell the temperature when to quench..  I had never heard that before..  :) 

Thanks on the info..  I'll shoot some photos of the original tomorrow..  I was going to make a split and run 2) 10" flexible round ducts 30ft long..  

For the return air I was going to go with a 21" round flexible duct. 

So the idea of having a wall for the air to smash into before moving on is not needed as a mixer? 

I did install a diverter into the bottom of the furnace (the side wall on the bottom) and this helped divert the air up and kept lotta the cold air from skipping by the heat exchanger. 

The temperature rise from ambient is substantial.  More then what is required consistently from this type of furnace.. 

When it's this cold out the temperature rise at the limit switch never kicks off just to blower because some of the cold air bypasses over the top of the heat exchanger so keeps the limit switch right around 150F.. 

Thanks for the help.. :) 

Link to comment
Share on other sites

Ohio,  It seems like things are progressing nicely..  the electric guys as long as they come back and do their work it will be moving ahead nearly on time..  

Few weeks the garage door will arrive, I can then put in the tube heater..  Once this happens the Lull can go home and I can get back to work on electrical.. As soon as the electric is in I can start making forges..   :) 

Link to comment
Share on other sites

Going to make me blush.

Salt trick I learned from Matt Parkinson.  It is a good one, but take care as molten salt is somewhat corrosive.  I haven't done extensive tests, as most of my blades get some grinding after heat treatment.  Still might be worth checking with a  scrap first if you are going for something with a final finish.

As regards your ductwork.  It is always easiest if we have a sketch, so we can be sure of configuration, but if I make the following assumptions:

  1. You will have a supply box plenum to transition between the existing furnace supply outlet and the (2) 30' long 10" flex distribution ducts
  2. You will have a sheet metal plate to transition to the single 30' long 21" round flexible return duct
  3. Your distribution airflow will be between 690 and 1500 CFM
  4. The furnace external static (ESP) is 0.5" WG regardless of airflow (unlikely, but presumably the reason for the (3) speed fan).

First let me say that as a HVAC engineer hearing that someone is going to use exclusively flex duct for their distribution system is like hearing that a smith will only be using a HF anvil.  It will work, but not as well as other alternatives.  Worst case scenario is for the higher flowrate:

  1. 30' of 21" flex duct at 1,500 CFM= 0.014 " WG loss (make sure you stretch it out to minimize ridges - typical for flex)
  2. Assume (2) 90 degree offset elbows in the 21" return duct= 0.012" WG
  3. Figure the supply plenum box at around 0.06" static loss (unfortunately winging this number as I don't have access to my ASHRAE duct database any longer)
  4. The 30' of 10" supply at half the overall flow is another 0.18" WG duct friction.

Totaled up this is only 0.266 " WG friction.  With a  typical 20% safety factor you are at 0.32 " WG friction which even allows something for the furnace filter.  In short, I would think your design should work for the supply and return of the unit in question.  Even if you do duct the return back to the unit you should still  include a certain percentage of clean outside air for ventilation.  The actual code quantity for that depends on the use of the space, floor area and projected number of occupants.  A relatively good rule of thumb is 20 CFM per person is typically adequate.  Note that most shops are not buttoned up tight and can use doors and windows to provide the needed ventilation via "natural" means (as opposed to mechanical using a fan).

Link to comment
Share on other sites

Thanks for the info..  

Keep in mind it's a portable heater..  Just move it where needed to get clean air heat..  Working on a car outside, need to heat up a tractor to get it started. etc, etc. 

The ducting is just to move the heat into a specific location. Like into the middle of the shop and thus heating from middle outwards.. 

.  I was originally thinking of moving the furnace from under the front roof to the side of it,  thinking the exhaust from the heater would accumulate under the roof but it seems to be ok. 

Being frugal I won't pay the highway robbery prices they want for "Heatwagon" flex duct.. 

And the people who have decent prices don't have any in stock to the middle of April..  

I'm mentioned this because once there is electricity and the garage door arrives and is installed, then the real heater can be installed..   So, at that point this heater will move into storage or the like.. 

* with that  Do you think having the plenum as described with a mixing plate in it?   Even worth it?  Just looking to get the air more even temperature before entering area. 

the duct adapter will just attach to what is there now. 

From what you wrote I'm guessing a 0 rise in WC is desired or the ideal..   The value I read was the maximum they wanted in a well designed system..   So ideally no resistance..   I wasn't sure if having some resistance would keep the air in and around the heat exchanger longer.   Looking to get every BTU I can.. 


the original was a 2 piece design joined in the middle.. that is what that seam is.. 

In my design there is a metal plate inside where the dotted line is.  with an opening on each side. 

Link to comment
Share on other sites

I now understand that this is for temporary heat only.  Flex is certainly acceptable in that case.

I would not put in the metal or perforated plate in your new plenum box.  If you want the air exiting the unit to be hotter, you can just turn down the fan speed.  Just keep the airflow above the minimum for the unit to avoid damage to the heat exchanger.

As far as heat content going into your shop, while there is a slight difference in efficiency of the heat exchanger, within the general parameters of the unit's allowable airflow the amount of heat supplied to the space will be the same whether it is mixed in the plenum or in the space where you are discharging.  As I mentioned, efficiency does come into it a little, but generally speaking the same heat is transferred into your shop if there is more hot air at a lower temperature or proportionally less hot air at a higher temperature.  In the equations heat content transferred is linear with both air flowrate and temperature differential (Q= 1.08 x CFM x (T2-T1).  Your backpressure design might improve the efficiency of the heat exchanger a little, but potentially at the cost of ruining your heat exchanger by overheating it.

Also note that supply air at temperatures in excess of 100 deg. F tend to stratify at the high points in your room volume.  The new model is to attempt to keep the supply air temperature below 90 deg. F where possible.

Link to comment
Share on other sites

16 hours ago, jlpservicesinc said:

Ohio,  It seems like things are progressing nicely..  the electric guys as long as they come back and do their work it will be moving ahead nearly on time.

Excellent. When I had to do the electrical in the Wonder Hut, though comparing the Wonder Hut to your project is like comparing mooning somebody to the moon landing, I found once I got going on it, everything flowed---it was quasi-Biblical in that And Then There Was Light. Regardless, good for you and I salute you. Good thing I'm wearing sweatpants, makes the saluting easier. Look, the moon is out.


15 hours ago, Latticino said:

Going to make me blush.

I accept your challenge. But first I need to buy a million feet of flex duct. And a HF anvil.

Srsly, dude, this is helpful stuff, even in a small shop. I was thinking of installing a small fume extraction and/or metal dust control system but I didn't want to half-moon (get it?) my way through it. If nothing else, the 20CFM per person guide is a place to start thinking about what I want to do and how.

And I'll bet I'm not the only one thinking about a shop build/re-build while following along here.

Link to comment
Share on other sites

Thomas its interesting what comes to your scrap yard, vs what ends up here.

Nearly all the industry is gone that used to be a meca for usable materials.  

Now not so much. But seems like not only variety at your place but constant turning over.

Going usta  be such a marvelous treasure hunt.

Link to comment
Share on other sites

Well the old stuff is off ranches, farms and abandoned mines.  People cleaning out old houses too.  The newer stuff is mainly from cars, farms and the University and University related industries.  At some point most of the old stuff will probably be gone---why I try to visit regularly now!  We had a mining boom 120 years ago that helped.  Not much population to produce a scrap stream before and after that.

One of my students family had a Manganese mine that was nationalized around WWII as they were not well compensated they took all the loose stuff they could from it.  Interesting to wander around his Grandmother's house in town with spools of steel cable and other mining gear---they had 2 anvils too.  My student managed to get one of them, his uncle---not a smith---grabbed the other.

Link to comment
Share on other sites

Ok, so went thru the first tank of fuel.. I wanted to run it all the way out.. It had a burner on time of 32hrs.. I'm guessing but believe the total fuel oil fill was somewhere around 24, 26 gallons. 

Today I actually filled it up till the filler neck was half full. It took 28Gallons.. 

It was 9F here this morning and pretty much all day it hovered around the 12F mark.. Windchill was in negative numbers. 

I started the furnace when I came back and lowered the fan speed so the limit switch would cycle on and off the way it should.   The fan is a 4 speed unit.. Thought it was 3 Hi, hi med, low medium and low.  

I wanted to test out the safety function so when it ran out of oil and stopped firing, it just went into hard lock out and shut the burner down completely..  Excellent.. this means I don't have to be overly concerned with a flame out and oil everywhere.   

When I filled it all the way back up, I hit the reset button and it auto primed (advantage of 2 line system) and fired up exactly as it was supposed to..  

Because of how cold it is, in high fan mode it was just to cold for the limit switch to work, so lowered it to low. 

I have to find a switch now that can be connected for high speed and low speed with just a flick.. that way I won't have to be switching wires.  

There is a 2 speed relay but not sure how to control it yet..  

Turns out the thermostat was never shipped and it won't be back in stock till the middle of april, so now I am looking for something else that is Wifi and uses batteries for the thermostat does not need to be mounted to the wall.. Aka portable. 

Here is a look into the work center of the furnace when just coming up to limit. 

The electric guys came back today and finished all the work so there is a nice new shiny transformer up..  :) 




Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...