I would love to see a DC blower and solar / DC variable speed pumps to run off grid. This is not so much for actually being off-grid but rather to have a heating system during extended periods of lost hydro. We were run out of our house last year after about 4 days without hydro and therefore no heat. I am not a big fan of using a generator but would rather go the DC route. Any suggestions out there?

DC or AC, you would need a very very large battery bank to deal with that sort of load.

 Not sure what the motor sizes are on these, but using a permanent magnet AC motor with a VFD (same principle as an electronically commutated DC motor) would save a fair amount of power.

Hi David: "Ivan Labs Inc. El Sid SID20B12 is a 20 watt 12 volt DC pump capable of circulating up to 6.0 gallons per minute of water. It operates from a 12 volt battery or bank of batteries. It can also operate from an AC to DC 12 volt wall adapter. The SID20B12 will begin to operate at 8 volts with as little power as 1 watt. This pump is designed to be used in radiant heat applications, hot water baseboard or with inside or outside hot water boilers. It uses 12 volt DC power eliminating the need for an inverter. Each SID20B12 pump only consumes 20 watts instead of the 150-200 watts a standard 120 volt circulating pump uses." http://www.renewcanada.com/ivan_labs_el_sid_sid20b12_pump.html As an added incentive, they are apparently manufactured in the US. In Canada they sell for about $360 Cdn. These are not variable speed but perhaps that is not necessary. My question about a DC blower still remains open.

Plenty of options for circulators, and given the duty cycle those are an important place to shop for efficiency.

The ID blower is where you're going to have a bit of a challenge getting efficient DC operation.  Fractional horsepower brushed DC motors are fairly common (mostly at 120V) but a VFD driving a 3ø induction motor (or ideally a PMAC motor) would be best.

Thanks mhotel for taking the time to . You appear well versed in this topic. It does appear that this is going to be the biggest challenge. I have been told that Martin (Lunde) has been looking for such a beast. I obviously do not know how much of a priority this has been however.

I visited a Garn customer site yesterday - there was a Dayton motor on the ID blower but I was not able to read the nameplate details.  The real answer here is to drive a 3ø motor (perhaps optionally a PMAC synchronous design) with a VFD that is coupled to a controller that responds to combustion temp and/or exhaust gases, probably with a PID loop.  This would modulate the ID motor speed up and down as the burn rate or other combustion needs changed.  If someone here has access to Martin Lunde, tell him I'd be happy to help though I'm an EE and not a combustion guy.

Mhotel Excuse my ignorance, but you seem to suggest that the blower is running at a variable speed depending upon load. I was under the impression that the unit ran at a constant RPM of around 3400. At any rate, finding a DC motor that will run at those RPM's is proving to be a little challenging for a novice like myself. If you are interested, here are the specs for the motor that comes with the 1500. Dayton does not seem to have a motor to fit this bill. In case you are not aware (unlikely), the blower bolt onto the motor listed below. Dayton 5K657BA Type: Cap. Start (Capacitor-Start) HP: 1/2 RPM: 3450 Voltage: 115 / 230 Full Load Amps: 8.0 / 4.0 Hz: 60 Phase: 1 Service Factor: 1.65 Thermal Protection: Auto Max Amb: 40oC NEMA Frame: 56C Mounting: C-Face Enclosure: ODP (Open Drip Proof) Bearings: Ball Insulation Class: B Duty: Continuous Rotation: CW/CCW Shaft: 0.62 x 1.88 w/1.38 Key Shaft Type: keyed Shaft Diameter: 5/8" Shaft Length: 1 7/8" Shaft Height: N/A Weight: 17.0 lb Nominal efficiency: 67.7 RPM range: 2350 - 3600

 I do not assume the existing ID blower is operating at anything other than full speed when it is on.

 I do assume varying that motor speed and architecture could benefit the system.  NEC Article 430 tables (required for conductor and overcurrent device sizing) give the following full load currents for 1/2 HP motors: 9.8A for 115V single phase motors and 2.2A for 230V 3ø induction motors.  These give 1127 VA and 876 VA respectively at full speed.  Add a VFD to the equation and the 3ø induction motor starts to look pretty interesting.  The preceding numbers are based on somewhat ancient NEMA Design B motors, which have fairly low efficencies.  Modern induction motors can easly beat this by 10% and a good PMAC motor can knock another 8-10% off of that.

Whoa there mhotel. You are WAY out of my league. I appreciate the time and effort you have put forth but have to be honest - I am lost. Are you saying that a DC blower is a possibility? If so, I should be looking for one with a Variable Frequency Drive right? Keep in mind that I am no engineer! :^)

 If you can find a DC motor with the correct shaft and face dimensions, that would work.

Variable frequency drives are used with 3-phase AC motors, usually induction motors.  The fist thing a VFD does is rectify and filter the incoming AC line to create DC.  This is used to supply a 3-phase inverter that is managed by a microcontroller in order to provide variable frequency, variable voltage AC to move the motor.  Thanks to the past couple decades' advances in power electronics, VFDs have become cheap, efficient, and widely available - you can buy small ones for under $150 and they run on single phase AC input power.  Some of them will accept DC input power (typically 120VDC or more.)

 

 Due to the fact the primary and secondary air metering is fixed, not independantly manipulated, you are not going to control the combustion by changing the volume of air through 2 fixed ports. Actually you will only create new problems , at low air volume you will induce puffing, not enough primary air to support combustion, at high airflow your stack temps will escalate because not enough residence time for the fluegas to shed heat effectively in the hx tubes and half of what will be going up flue will be the result of partially processed fluegas not having the residence time to reburn properly, all reducing effiency. The above answers are from my trials with exactly what you are suggesting, i used a insitu fluegas analyser displaying a o2 from 0-20.9% that output a 4-20mA control signal to a allen bradley plc that output a setpoint signal to a hitachi inverter that drove a 2 hp/3 phase 56c frame motor. The range of manipulation was 0 hz to 90 hz. There are more effective ways to actually control the process

As a Garn rep I see and hear a lot of talk about re-engineering the best woodburning equipment in its class. To those who feel a need to do this there is a couple of things that should be considered. Martin Lunde is not only a very competent and well schooled engineer he has made a life study of wood burning technology and how it applies to the Garn product. For 35 years, I doubt a day has gone by, that he has not given thought to how he can improve the Garn and I don't believe that there is anyone on this forum that can out maneuver him in a brain wrestle. (How many waking hours are there in 35 years?) 

There are a lot of really intelligent people posting to this site (most more intelligent than myself) and I do not in any way mean to disparage anyone. It is often very thought provoking and valuable, but I think it is worth stating that every conversation taking place at the Garn offices includes ideas about how the product could be better without sacrificing safety or efficiency. What we have is really good and it's not easy to come up with improvements, but we will because it is our goal.

That was kind of a long preamble to the original point I set out to make, but it is a very important point to remeber. If you modify your Garn product in any way you will void the listing and the warranty. I hope this post does not come off as "preachy" because I really enjoy reading about everyones idea's and you should all know that we are listening.

 Nice to know that someone has tried modulating the ID airflow.  I remain convinced that some kind of active control presents an opportunity to optimize combuston across different fuel types and loads.

 The existing static ID airflow design and single phase motor have plenty of potential of reduced electrical load, for which some users would happily pay a premium.

I am not an engineer either. We will be purchasing either one 2000, or maybe 2 1500's if I can get some more grant contribution. I understand the 2000 have a 3/4hp motor, the 1500 a 1/2 hp motor We looked at PV, we would be grid tied, the numbers do not add up . But if you are off grid, the extra cost of much more efficient motors is likely to be a lot less than installing extra capacity. Control of the burn is another issue. One of the plus points for the Garn is its very simplicity, Lambada control etc is very nice, but it would have to make a big impact for me to consider.