RK-2001U blowing fuses

[Shelterman]

Since it's been relatively warm here in southern Missouri and I have a 1000 gallons of storage I haven't had to fire my Biomass 60 for a couple of days, so last night I loaded and fired up my Biomass 60. Just as things started going real good the Biomass suddenly went completely dead...including the controller display...everything. Luckily I have my circ pump wired with a UPS to dump into storage in the event of a power outage so I was able to at least power the pump till the boiler cooled down.

After a bit of troubleshooting I found that the fuse on the RK-2001UA controller had blown. When I replaced the fuse and tried to turn the furnace on, the display briefly flashed on and the fuse immediately blew again. I then disabled the pump and draft fan. This time the firebox fan came on, the controller lit up and stayed on and seemed to operate correctly, including all the functions on the controller. I then plugged in the draft fan and the fuse immediately blew again. After going to town to purchase more of the rather uncommon GMA glass fuses, I tried it again, this time with the firebox blower and the circ pump wired in, and only the draft fan disabled. Again everything seemed to work until I again applied the draft fan...BAM!...fuse blew again!

The draft fan itself works just fine when I apply line voltage to it directly. I don't have a lot of electrical knowledge, but it seems odd to me that this fuse, being just a 2A fuse, is blown by the current draw of the draft fan when the fan itself probably draws more than 2A, so I don't see that it would be the fan causing the problem. Could it be the controller itself? I'm kinda stumped here and don't know what to try next.

I've had the boiler for 3 years so I suppose it is covered under warranty, but I'm not sure what to ask to have replaced.

Any suggestions would be appreciated.

David

 

[STIHLY DAN]

Does the fan plug into the board? Contactor? Relay?

 

[mr.fixit]

Does the draft fan have a capacitor?
If so I would try that

Also might want to check the wiring between the controller and fan for shorts.
When you tried the draft fan directly did you connect it where the fan wiring connects at the controller or directly on the fan?

 

[Shelterman]

Does the draft fan have a capacitor?
If so I would try that

Also might want to check the wiring between the controller and fan for shorts.
When you tried the draft fan directly did you connect it where the fan wiring connects at the controller or directly on the fan?

The draft fan has a metal encased compartment attached to the motor of the fan, which I would call a "starter". Would the capacitor be in this? The draft fan has a short corded plug. I plugged this directly into an extension cord. The draft fan worked just fine when I did this.

The draft fan 120v wires plug directly into the back of the controller. If I attached 120v to them, (while removed from the controller of course), with alligator clips and it powers up from there without blowing a breaker would that eliminate the possibility of a short somewhere between the fan and controller?

 

[Shelterman]

Does the fan plug into the board? Contactor? Relay?

The fan has a short plugged cord which plugs into another female cord which is wired directly to the controller. Here is a schematic:

 

[rkusek]

What percent is the fan speed set at? I've never had any reason to investigate but I assume the fan speed is controlled by the RK changing the frequency of the 120V output. If it works fine when the fan cord is plugged separately it sure sounds like something in the RK controller has failed. I suppose it's possible that the fan could be drawing more than it is supposed to as well. Does is seem to drag more than before? You might be able to wire in a relay connected to a separate fused 120V source, with it's coil triggered by the RK controller's fan output. You would lose the variable speed both in the settings and also when it does it's fan slow down when approaching it's setpoint temperature. While that may work as a temp fix, I think I would get it replaced under warranty.

 

[ewdudley]

Just some suggestions:

(What RK says!)

Get a $15 AC ampere meter from HF or wherever and find out what the fan motor is drawing when it starts and when it's running.

(e.g., http://www.ebay.com/itm/MT-87-AC-DC...717?pt=LH_DefaultDomain_0&hash=item3f290cab05
Must separate leads to motor and run only one lead through loop.)

Lubricate the fan motor with Wurth Sabesto HHS 2000 lube, or ATF in a pinch.

[Edit:] See below, slow blow fuse may be bad advice.

You could switch to a slow blow fuse that may be more suitable for motor starting, but this doesn't address the root cause.

 

[Shelterman]

You might be able to wire in a relay connected to a separate fused 120V source, with it's coil triggered by the RK controller's fan output.

That is an interesting idea. I actually have a relay that would work for this. I may try this until a more permanent repair is made.

 

[Shelterman]

Get a $15 AC ampere meter from HF or wherever and find out what the fan motor is drawing when it starts and when it's running.

Yeah, I do need to get one of these. I may not have the knowledge to use it to it's full ability, but it would come in handy sometimes. My basic voltmeter has its limitations.

You could switch to a slow blow fuse that may be more suitable for motor starting, but this doesn't address the root cause.

I did notice that the package that the fuses came in say "fast blowing". I will look for slow blowing.

 

[Shelterman]

What percent is the fan speed set at? I've never had any reason to investigate but I assume the fan speed is controlled by the RK changing the frequency of the 120V output.

Since I have storage, I run everything at 100% with no ramping down of the fans. When storage reaches the desired temperature or when the fuel runs out and the flue thermostat cuts the power to the fans, the fans just shut off.

 

[ewdudley]

Since I have storage, I run everything at 100% with no ramping down of the fans. When storage reaches the desired temperature or when the fuel runs out and the flue thermostat cuts the power to the fans, the fans just shut off.

Exactly. The RK-2001U fan control function makes no sense to me when boiler is heating storage. I could see it if fan speed was a function of flue temperature.

 

[ewdudley]

Yeah, I do need to get one of these. I may not have the knowledge to use it to it's full ability, but it would come in handy sometimes. My basic voltmeter has its limitations.



I did notice that the package that the fuses came in say "fast blowing". I will look for slow blowing.

Sorry, the slow blow advice may be a bad idea. Solid state switching devices may need fast fuses for protection:

http://www.epanorama.net/circuits/semiconductor_relays.html :

You can use a more appropriate fuse (faster and more expensive) and/or use an over-rated triac. Fast, "Semiconductor Fuses" are the only reliable way to protect SSR's. They are also referred to as current-limiting fuses, providing extremely fast opening while restricting let-through current far below the fault current that could destroy the semiconductor. This type of fuse tends to be expensive, but it does provide a means of fully protecting SSRs against high current overloads where survival of the SSR is of prime importance.

 

[Fred61]

I'm no expert on motors. In fact I don't even make it to amateur status but I think EW's suggestion should be the first thing to do. If the readings add more confusion, you could replace the starting capacitor for a couple bucks and try that. The fact that the controller is actually switching on tells me that the problem in downstream.

 

[STIHLY DAN]

Look on the female cord for damage. Why not try plugging some other device into the female end and see what happens. lamp or utility light.

 

[Shelterman]

Look on the female cord for damage. Why not try plugging some other device into the female end and see what happens. lamp or utility light.

Good idea. I will try this when I start trying to trace the short.

 

[Shelterman]

Update... Since I had a relay on hand I wired up the draft fan as rkusek suggested, using the draft fan output from the controller to energize the relay which was used as a switch to apply 120v from another source to the turn on the draft fan. It worked like a charm! I guess that tells me that I either have a short in the wire going from the controller to the draft fan or the capacitor on the fan is bad. I tested the draft fan wire for a short with my voltmeter and couldn't get any continuity from either of the wires to the chassis of the Biomass. I know that doesn't eliminate the possibility of a short in this wire though. This was the extent of my searching to find out what the problem was as I didn't really have time tonight to do much other than try to get producing heat again. I'll try to concentrate on finding the problem tomorrow. I'm just glad that the controller still seems to be working, that was my biggest worry.

Thanks to everyone for their input, especially rkusek's relay suggestion. That has at least got me up and running again. I'll give another update tomorrow.

 

[rkusek]

Glad to hear it doesn't sound like the controller and you were able to make heat with the relay. Check your continuity with the draft fan wires to themselves not just to the metal chassis (the cord has 3 conductors right Line,Neutral,Ground?). I'm not sure how similar the Biomass is to the EKO but it would be easy to hook a new cord up externally to verify the cord is bad first before replacing the original with it. Hardware store should sell something like the original by the foot. I've had broken wires inside insulation before that made contact part of the time which made it very hard to diagnose the problem. I think the Harbor Freight $11.29 clamp-on ammeter EWD mentioned would definitely be a good thing to check how many amps the fan is pulling but it sure sounds like the cord is the problem.
http://www.harborfreight.com/digital-clamp-on-multimeter-95652.html

 

[Shelterman]

Glad to hear it doesn't sound like the controller and you were able to make heat with the relay. Check your continuity with the draft fan wires to themselves not just to the metal chassis (the cord has 3 conductors right Line,Neutral,Ground?). I'm not sure how similar the Biomass is to the EKO but it would be easy to hook a new cord up externally to verify the cord is bad first before replacing the original with it. Hardware store should sell something like the original by the foot. I've had broken wires inside insulation before that made contact part of the time which made it very hard to diagnose the problem. I think the Harbor Freight $11.29 clamp-on ammeter EWD mentioned would definitely be a good thing to check how many amps the fan is pulling but it sure sounds like the cord is the problem.
http://www.harborfreight.com/digital-clamp-on-multimeter-95652.html

Yeah, I also tested for continuity between all of the conductors too. All seemed ok. I'm going to try Stihly Dan's suggestion tomorrow and try to power up a drop light or something through the internal cord. However, I'm gonna have to wait till my order of spare fuses comes in before I get any more daring with the controller. I've gone through all of the GMA fuses that were available in my small town and am now down to my last fuse which is currently in the controller. That is why I liked the relay idea so well, the only current I had to draw through the controller was to energize the relay. There was a lot less risk of blowing my last fuse using the relay than bypassing the internal cord as you suggested above if it indeed turns out that my fan is drawing more current than it should. I paid extra for express delivery, so the fuses should be here in another day or two.