OWB thermostat question

[applefarmer]

My hawkin owb uses a simple mechanical thermostat that turns the blower on and off at set points. It has worked perfectly but I would like to have the blower shut off if the water temp gets below a certain point, instead of constantly running. I think woodmaster uses a programable thermostat which allows this, I don't know about any of the others or the ranco thermostat. Let me know if you have any ideas, thanks.

 

[Labman]

Any old air conditioning thermostat should work. Red is hot from the transformer. Yellow controls the A/C compressor.

You need a 24 volt transformer and a 24 volt coil relay. Connect one wire to the coil of the blower relay to the Y terminal. Connect one side of the transformer to the R or RC terminal of the thermostat, and the other to the second coil wire. When the thermostat reaches the set point, it will break the connection between RC and Y. shutting off the blower.

 

[applefarmer]

I think I should have said aquastat instead of thermostat, and I am talking about the forced draft blower on the owb.

 

[AIM]

I think I can guess what your after but wouldn't it end up being a pain in the arse for those "cold starts".
You would end up wanting a bypass switch so the blower would run until you reached your set point for blower shut off. (really hard to explain)

For example
You forgot to load the boiler before you left for your cousin Tyrones wedding.
The fire burns down and the water gets down to 120 when your blower shuts down.
By the time you get home your water temp is down to 100.
Now you have to rely on natural draft alone until the water is up to 120 when your blower will turn on again.

If you had a bypass switch you could flip that to make it run but then you would have to remember to switch it back to normal operation after the water temp returned to normal temps.

"IF" my thinking is right it would be more of a pain that it would be worth.

 

[Laird]

I think I can guess what your after but wouldn't it end up being a pain in the arse for those "cold starts".
You would end up wanting a bypass switch so the blower would run until you reached your set point for blower shut off. (really hard to explain)

For example
You forgot to load the boiler before you left for your cousin Tyrones wedding.
The fire burns down and the water gets down to 120 when your blower shuts down.
By the time you get home your water temp is down to 100.
Now you have to rely on natural draft alone until the water is up to 120 when your blower will turn on again.

If you had a bypass switch you could flip that to make it run but then you would have to remember to switch it back to normal operation after the water temp returned to normal temps.

"IF" my thinking is right it would be more of a pain that it would be worth.

:agree2:

If you plan on not burning for a few days and don't want the fan to run just flip the switch to shut the fan off , you can take the light bulb out if you don't want that on either.

 

[applefarmer]

I think what I want is a low temp limit switch with a manual override. The problem is I don't know where to look for it. I had hoped some of the shaver guys would chime in since I think they end up using the rancos.

 

[Butch(OH)]

You correct about the Woodmaster set up and I understand why you want it, to conserve heat in the system when it goes low on fuel. The older aquastats had hi-limit capibilites but I dont know about low limit, I assume you have checked that out? All you need is a loop temp contolled cut out in the wire feeding the fan. You might try going to WW grainger on line and looking through the controls section. The race car places sell exactly what you need, an adjustable make break switch to controll the electric fans on race cars except I am not sure if they are rated for 110V. Jegs sells them for like $40 and are usualy pretty good with tech help. My bet is there is a HVAC specific item that will do the job but I am no HVAC man.

 

[projectsho89]

I think what I want is a low temp limit switch with a manual override. The problem is I don't know where to look for it. I had hoped some of the shaver guys would chime in since I think they end up using the rancos.

The single stage Ranco will not perform this task. The dual stage Ranco might, but I haven't looked too closely at that option.

I'm installing this feature this weekend on my NCB along with a high-limit cut-out for the damper solenoid and blower.

I'm going to use a simple upper water heater thermostat (White Rodgers 756-1 or equiv.) set for around 110F with a standard light switch in parallel with it as a manual override.

My operating strategy is as follows:

Out of fuel, water temp drops below set-point, thermostat opens removing power from damper solenoid and blower. Unit sits there until I get back. Reload it and start fire again if needed. Flip override switch on to bypass cold thermostat. At some point after the boiler is up to temp, switch off override.

My pump will be controlled from indoors via a custom controller I've been working on. Currently, I've got it wired so that the main pump is wired in parallel with the furnace blower. I'm using the analog output of my Ranco and using it to control three separate functions:

1) Gas/OWB arbitration: If below a minimum temp (around 120 F), activate furnace in normal propane mode on house thermostat heat demand. If above set-point, turn on pump, delay 60-90 seconds (still working on this part), then turn on furnace blower.

2) Boil-over prevention: If boiler reaches high limit (190-200F), turn on pump to circulate water and "dump" excess heat by running it though the HX and tubing. My boiler tends to have the water temp creep upward as the door and ash drawer seals don't always get seated properly. Twenty minutes of circulation usually mixes the water enough to drop the boiler temp back to normal limits.

3) Vacation mode: If boiler temp hits a very low limit, perhaps 50F, run pump continuously to prevent freezing (vacation mode).

Since I datalog my system's operation, I can monitor both its current status and its recent history. My datalogging is running on an old laptop down in the basement running XP that is connected to my home network wirelessly. I can sit at either my desktop or at my laptop (anywhere in the house but usually next to my recliner) and see what is going on. As long as my internet connection is working, I can also log in from anywhere while away and see what the boiler is doing. :hmm3grin2orange:

 

[Butch(OH)]

Since I datalog my system's operation, I can monitor both its current status and its recent history. My datalogging is running on an old laptop down in the basement running XP that is connected to my home network wirelessly. I can sit at either my desktop or at my laptop (anywhere in the house but usually next to my recliner) and see what is going on. As long as my internet connection is working, I can also log in from anywhere while away and see what the boiler is doing. :hmm3grin2orange:

Wow, I wish I was that savy around a 'puter. I do worry about being away from it all day when nobody else is home either. I have a Blackberry now and could,,,,,,,,

 

[projectsho89]

I just wish I'd learned Visual Basic or ActiveX. If I knew those, I could control the whole thing from the laptop instead of designing the circuitry from scratch.

 

[jimdad07]

I agree with what is said above about it not coming back on. If you can live with that aspect, I think the simplest thing you could do is get a refrigeration temperature control that has a common, open on rise and open on drop terminals. You can break the hot leg to the draft motor and strap the temperature probe to the water piping. You want to wire one side of the hot leg to common and the other side of the hot leg to the open on temperature drop. The only problem is that the water temp has to rise to bring the fan back one.

 

[projectsho89]

I agree with what is said above about it not coming back on. If you can live with that aspect, I think the simplest thing you could do is get a refrigeration temperature control that has a common, open on rise and open on drop terminals. You can break the hot leg to the draft motor and strap the temperature probe to the water piping. You want to wire one side of the hot leg to common and the other side of the hot leg to the open on temperature drop. The only problem is that the water temp has to rise to bring the fan back one.

Well, if the water temp has to rise to turn the fan back on and the water temp cannot rise without the fan, you're going to need a manual bypass or other manual intervention, I suppose, eh?

A simple bathroom fan timer would do the job if you know how long it usually takes to get back up to temp when refired if you don't want to use a simple $1 light switch that you might forget to reset.

 

[applefarmer]

Thanks for the replys! I am still thumbing through the grainger catalog looking for the least complicated way to do this. In an ideal world they would make a progamable digital aquastat, with high and low set points and adjustable "saftey" high and low points. I would also like to be able to have my progamable boiler aquastat on a timer so at 5:00 am it would bring the water temp up to 180-190 right before the house is calling for heat, showers are taken and, the garage is open and shut. Then kick back down to my defalt 135 on 165 off (which is all I have now). I will keep looking, keep the replys coming!

 

[ngzcaz]

I think what I want is a low temp limit switch with a manual override. The problem is I don't know where to look for it. I had hoped some of the shaver guys would chime in since I think they end up using the rancos.

Several guys have indeed gone to Rancos etc.. some holdouts like me just fiddled with the stock one and got it where it was acceptable.. Draft motor mod was a no brainer for a whole lot more folks than any other change I'd guess. What I do find interesting is that a lot of guys will fiddle with almost anything. I like it.

:hmm3grin2orange:

 

[Stihl310]

The single stage Ranco will not perform this task. The dual stage Ranco might, but I haven't looked too closely at that option.

I'm installing this feature this weekend on my NCB along with a high-limit cut-out for the damper solenoid and blower.

I'm going to use a simple upper water heater thermostat (White Rodgers 756-1 or equiv.) set for around 110F with a standard light switch in parallel with it as a manual override.

My operating strategy is as follows:

Out of fuel, water temp drops below set-point, thermostat opens removing power from damper solenoid and blower. Unit sits there until I get back. Reload it and start fire again if needed. Flip override switch on to bypass cold thermostat. At some point after the boiler is up to temp, switch off override.

My pump will be controlled from indoors via a custom controller I've been working on. Currently, I've got it wired so that the main pump is wired in parallel with the furnace blower. I'm using the analog output of my Ranco and using it to control three separate functions:

1) Gas/OWB arbitration: If below a minimum temp (around 120 F), activate furnace in normal propane mode on house thermostat heat demand. If above set-point, turn on pump, delay 60-90 seconds (still working on this part), then turn on furnace blower.

2) Boil-over prevention: If boiler reaches high limit (190-200F), turn on pump to circulate water and "dump" excess heat by running it though the HX and tubing. My boiler tends to have the water temp creep upward as the door and ash drawer seals don't always get seated properly. Twenty minutes of circulation usually mixes the water enough to drop the boiler temp back to normal limits.

3) Vacation mode: If boiler temp hits a very low limit, perhaps 50F, run pump continuously to prevent freezing (vacation mode).

Since I datalog my system's operation, I can monitor both its current status and its recent history. My datalogging is running on an old laptop down in the basement running XP that is connected to my home network wirelessly. I can sit at either my desktop or at my laptop (anywhere in the house but usually next to my recliner) and see what is going on. As long as my internet connection is working, I can also log in from anywhere while away and see what the boiler is doing. :hmm3grin2orange:

Just curious, are you using Labview software to achieve this?? I have this program on my laptop and would someday like to get a "junker" desktop that I could load it onto and then operate the woodburner via the software (this is years down the road), I love tinkering with stuff and think this would be a great way of controlling and monitoring the system. Granted it would probably cost thousands of dollars to implement all of the relays, thermocouples and what not... but it sure would be cool.

 

[Stihl310]

Thanks for the replys! I am still thumbing through the grainger catalog looking for the least complicated way to do this. In an ideal world they would make a progamable digital aquastat, with high and low set points and adjustable "saftey" high and low points. I would also like to be able to have my progamable boiler aquastat on a timer so at 5:00 am it would bring the water temp up to 180-190 right before the house is calling for heat, showers are taken and, the garage is open and shut. Then kick back down to my defalt 135 on 165 off (which is all I have now). I will keep looking, keep the replys coming!

Maybe I'm wrong, but could what you want to do be achieved with a simple NC snap disc thermostat that would break at "120" degrees or wherever you wanted it??? Then just wire a switch in, in paralell that if you were below this setpoint you could manually run the fan to get back up to tempera ture... You may then want to wire in some sort of indicator light in series with the switch as a visual to when it's on/off... I'm throwing this all out off the top o my head so there may be some fault in my logic... If this would work it weould definetly be the easiest to wire in and maintain... I have tossed around doing this for the simple fact that on the weekends I tend to sleep in and sometimes find my OWB out of wood with the damper and solenoid engaged.... THinking this is what you want to do...

 

[jimdad07]

Maybe I'm wrong, but could what you want to do be achieved with a simple NC snap disc thermostat that would break at "120" degrees or wherever you wanted it??? Then just wire a switch in, in paralell that if you were below this setpoint you could manually run the fan to get back up to tempera ture... You may then want to wire in some sort of indicator light in series with the switch as a visual to when it's on/off... I'm throwing this all out off the top o my head so there may be some fault in my logic... If this would work it weould definetly be the easiest to wire in and maintain... I have tossed around doing this for the simple fact that on the weekends I tend to sleep in and sometimes find my OWB out of wood with the damper and solenoid engaged.... THinking this is what you want to do...

I think you have a good idea there. Not too many options for him to get the fan running oince it drops below setpoint. On the other hand, Ranco makes an electronic temperature control that might do what he is looking for, it works for both heating and cooling with a normally open and a normally closed switch internally. You can do a very basic programming on them that might get him what he is looking for.

 

[Stihl310]

I think you have a good idea there. Not too many options for him to get the fan running oince it drops below setpoint. On the other hand, Ranco makes an electronic temperature control that might do what he is looking for, it works for both heating and cooling wiopen and a normally closed switch internally. You can do a very basic programming on them that might get him what he is looking for.

I have the basic Ranco on my homebrew right now... It is very simple progamming, basically all I have on mine is heat/cool option, temp setting, and temp differential setting. I'm thinking it would take more to get what he wants... The easiest (maybe not easiest), but a simple way of doing it would just to be to install a PLC and write the ladder logic to do exactly what you want... albeit this would not be cheap... If/when I build another one I'm either going to put a PLC on it or run it through LabView... Labview, although the expensive route, would no doubt be the coolest, you could sit on your recliner and change temperature, turn your pump on off, run you blower fans and so on... I can't guess what it would cost to put it all together but it wouldn't be cheap.

Anyways, back to the original post... LOL... Hopefully what I threw out there could help you.. In my mind I think that would be the easiest and cheapest way of doing it.

 

[projectsho89]

Just curious, are you using Labview software to achieve this?? I have this program on my laptop and would someday like to get a "junker" desktop that I could load it onto and then operate the woodburner via the software (this is years down the road), I love tinkering with stuff and think this would be a great way of controlling and monitoring the system. Granted it would probably cost thousands of dollars to implement all of the relays, thermocouples and what not... but it sure would be cool.

I don't have Labview available. I'm using the "free" software that is included with the DATAQ DI-148.

BTW, I got the custom circuit onto a breadboard and online a couple of days ago, right before I left town for the weekend. I started up the data logger software around 11 on Friday morning and the wife and I hit the road for the weekend. Thirty minutes later a storm came through and knocked out our power so I didn't get any of the expanded functions logged all weekend...


Now to add monitoring of the pump's cycling and the OWB's blower...

Bad thing is, I really need to go cut some more wood, but I've been playing with the circuitry instead!

 

[Stihl310]

I don't have Labview available. I'm using the "free" software that is included with the DATAQ DI-148.

BTW, I got the custom circuit onto a breadboard and online a couple of days ago, right before I left town for the weekend. I started up the data logger software around 11 on Friday morning and the wife and I hit the road for the weekend. Thirty minutes later a storm came through and knocked out our power so I didn't get any of the expanded functions logged all weekend...


Now to add monitoring of the pump's cycling and the OWB's blower...

Bad thing is, I really need to go cut some more wood, but I've been playing with the circuitry instead!

That's interesting... too bad aboout the power outage... I have a breadboard/software called CUBLOC, it's basically a breadboard setup with a programmable chip that gets plugged in to the board. Then on the software you use a combination of Visual Basic code, along with ladder logic to program the chip. Once the chip is loaded with whatever code you have written, it will hold that program indefinetly. The only problem is the current chip that I have on it is that it only has 8 inputs and 8 outputs. It's also only a 5V system, so I would have to use extensive amounts of relays to actually run the wood burner. I suppose just monitoring it wouldn't be so bad.

THe good thing is, if I ever did hook up the CUBLOC, all I would have to do is purchase an additional chip that would plug into the board, I know for sure you can get one with 16 inputs and 16 outputs... Think it's around 100$.

Anyways, the only reason for having to use Basic code is to "basically" declare what inputs/outputs you'll be using, and to throw the code into a loop so it keeps recycling. Then when you write the ladder logic, you just assign the pin nyumbers you declared in Basic, to the switches/outputs on the ladder logic... It would probably be more hassle than it's worth to get it all hooked up, but it would be a fun little project. I imagine if I ever do it I'd just purchase a SLC500 Allen Bradley PLC and tie that into the system... be much easier, and the programming software is more readily available.

Pretty interesting what your doing though, I'd be interested in hearing how it all works out for you in the future.