I've got to vent... No, really, I HAVE to vent! - Page 1
Forum section: electronics / general

author: BBQdChips
author_rank: Contributor
timestamp: April 09, 2012, 01:13:33 am
content: This is sorta long... Sorry, but I've got to vent after this one.So, three years ago, I decide my house deserves a new furnace. It's an oil fired boiler, and while I'd liked to have gone to coal fired boiler, I didn't. I only use it as backup heat for the house and hot water off the boiler. So, I didn't want to go thorugh that additional trouble and expense. Another oil furnace is just a bolt in replacement, a couple copper pipes and a few wires. Everything is there, it's easy.So, I go to a local place that sells boilers and they tell me yep, I can buy it but it'll have to be done through an "Approved, installer". ?? Huh? Look, I want to buy a boiler, and I'm gonna hook it up myself. Simple.No no, you need a certified person to do this cause it's dangerous and bla bla bla. We can't sell you one... Ok, so how much is installation? $3000. Are you smok'n meth or what? Yer outa yer (*&^* mind!Ok, well, I'll tell ya what. I can go to Lowes and buy one and leave with it so tell me again what it is that is so dangerous... I own my own Baccarach gauge because the last dipshit who worked on a furnace for me, set up the burner so far off it about asphyxiated everyone in the house. SOOO, do you want to sell me one or do I have to go elsewhere? ... Went elsewhere...Call the place that does our furnace service at work, and sure, they'll deliver one for me any day, just tell em where to drop it off, I can just pay whenever they send the bill. No problem. Wow, that was easy!My chimney is old, (the house is old) and the terracotta is deteriorating, so I wanted to either get a new chimney put up or use a powervent. After some deliberation, and despite the fact that the powervent cost more than a 35' chimney replacement, I decided to do the powervent. According to what I was told by a few people, they were just the dogs breakfast... I live in an area with considerable wind, and thought this was a great solution.I installed this myself as well. I was told that the warranty was only on the fan if I installed it. Ok, well, I'll take my chances, I think I can handle 6 wires. So, off I go.So, one day passes and I have my furnace installed and everything is back to normal. Got the burner running at 86% efficiency, ok, life is good. What's more, I actually sized the furnace properly for the house, unlike the last person who put one in.Everything runs great for 6 months. Other than the fact that the powervent is no better at dealing with wind than the chimney. In fact, it's worst. But, then one fine morning I wake up and it's cold and there's no hot water. The furnace is completely dead, and reseting it will not make it even attempt to start. It's really dead. After some looking, the powervent seems to be stopping the thing from starting. So, I bypass that quickly and whoosh, the furnace attempts to start. I stop it and open the box for the vent control, and low and behold, a component on the board is burnt, and the thing is dead'er than a doornail. Ok, well, I have to get a shower and go to work so I simply hard wire the fan on with jumpers, bypass the vent and fire up the furnace, get my shower, shut it all off and leave. I'll deal with it later. I take the box with me to work so I can make calls.I call the company and they say, well, there's no warranty on the board, and it's $300 for this thing. I tell em this thing isn't 4 inches square and there's nothing on it? Wth? Well, I come unglued and tell them in no uncertain terms this thing worked for 6 months, and the only reason it's dead is cause it's a piece of shit. You've got to be joking, a couple relays and a vacuum switch, and I'm keeping the switch? Get serious. The thing only has a one year warranty anyway, somebody better be coughing up a board for me or you'll wish you had. There's resistors on this board that are raised off the surface cause you KNOW they get hotter than hell, who designed this piece of junk? This'll be on the news if I don't get a board...So they tell me they'll make an exception, no problem, we'll replace the board.So, this board, a new rev, lasts 2.5 years till about a month ago, the furnace began shutting off for no apparent reason. I have no time for this crap right now. Reseting the thing appears to make it run ok, and it sometimes runs for a few days, sometimes for a few minutes. Flip a coin, it's anyones guess when it'll stop. So, I ask a few friends who do furnace work what else it can be. I've replaced everything burner related and still, this thing is acting very strange. The flame is all but perfect, there's not enough dirt in it to warrant a cleaning. Putting your hand in the stack pipe results in a clean hand coming out. It is burning so perfect I've never seen the likes of this. So, what's up? One tells me to clean out all the lines going to the furnace, maybe they're blocked, etc. Sensors, nozzles, he even gave me a furnace control to try and see if that was it. It wasn't.Last item, I cleaned out the oil supply line, and low and behold, bled the air, fired it up, it ran for an hour, quit, I reset it and it ran for 3 weeks. Well, thank gawd, that's done...Till Friday... Get up in the morning, no hot water... Oh for the love of gawd, now what. More teardowns, more cleaning, there simply is nothing on this burner left to replace. Till today, I'm messing with it for a few hours and one time, I hit the reset button to fire it up, and ... nothing. Not a sound... AHHHh HHAAAAAAA, I know what does this sh&^^$! YOU (*&$#* (&%*$( (&%($* (&$%. The fan never even tried to start. The first it did this. It should turn on for 15 seconds before the boiler fires. Now, up to this point, it has "Appeared to work" every time. What I did not pick up on was that when I did see the thing shut down, the "post-vent" didn't run. Or, at least I don't remember it. It's supposed to run for 20 seconds after the furnace stops to get all the gasses out of there. OOOOKKKK...Well, I've got a cure for that too! This is the last straw. Back to the chimney, I don't care, I'm not dealing with this on Easter Sunday all day in diesel fuel. Enough... Pull open the powervent box and what do I see? More resistors burnt to a crisp... It's not driving the relay to run the fan, basically, it works just enough when cold to make you think it's the burner.Now, the irony in all this is that there are people who would say I am not allowed to do my own installation for fear I might make a mistake. But! Some jackass is allowed to design this worthless control and get it "Approved" and that's all ok??? What is wrong with this picture?!!!What's worse, this board STILL had the one resistor jacked up off the board so it would not burn nearby components or desolder itself. Now, if they KNEW this is an obvious problem... I'm speachless. Wth? Like there's no way to power a relay and turn on a 1/5hp fan/pump without setting resistors on fire? Now, I'll admit, I'm not an EE with a degree or anything. Ok, but even still, I could easily breadboard a PIC here tonight with a couple solid state relays and do what this piece of shit did without generating a lick of heat. It just amazes me that this is the sort of quality built in America any more. Yes, sadly, this was made in North Carolina. I paid 'Made in the USA' Dollars for it, but got 1920's chicom quality.Here's a pic of the board that costs $300, and work long enough that it's only about $1000.00 per year to keep one going!

author: IanB
author_rank: Super Contributor
timestamp: April 09, 2012, 01:33:22 am
content: Such is life.I guess the path of least resistance (pun not intended) is to repair the board by replacing the burnt resistors with bigger ones having a higher power rating? Sometimes resistors just have to get hot and the best way to deal with it is to handle the heat so it doesn't damage things.(Oh, and just an obligatory nit-pick since you clearly need some extra winding up, a furnace is not a boiler and a boiler is not a furnace. A boiler "boils" water--hopefully not literally in a domestic situation--and a furnace heats air. If you have something that heats both water and air, then I suppose it is a heater?)

author: Rerouter
author_rank: Super Contributor
timestamp: April 09, 2012, 01:35:31 am
content: logic would tell me to replace those resistors with 3W resistors, as a quick and more reliable fix, even better would be to find leg sleeves, (little white sleeves to keep the resistor rigid when raised high from the board) so you can raise them more than 1cmedit: also those non insulated crimps make me feel like saluting american made products with a smug grin of sarcasm on my faceplease tell me there is atleast a connection to earth on that metal casing

author: BBQdChips
author_rank: Contributor
timestamp: April 09, 2012, 02:54:21 am
content: Quote from: IanB on April 09, 2012, 01:33:22 amIan,I'm not gonna bother getting wirewounds and trying to fix it. The whole thing is too flaky and does too much weird stuff to keep throwing good money after bad. I mean, the basic design is terrible. Considering the venter itself, it has the fan that is outside the house, and a 4 inch tube that comes inside. In that tube, there is a gate which allows you to limit the amount of air it pulls through the ... furnace... (I'm gonna stick with my terminology, it's what the units manufacturer calls it, referring to the heating part, and the water vessel / heat exchanger parts).Anyway, they have another tube coming in behind the fan, but in front of that gate, which then connects to this vacuum dashpot switch gizmo and checks to see there is enough negative pressure in the system. But, it is in front of the gate, so, if I open the gate and allow it to pull lots of air from the burner, then it has very little negative pressure, and shuts the system down. If I close that gate and don't allow it to pull the gasses out, then it thinks everything is ok because it's seeing lots of negative pressure right behind that fan. Of course, burnt gas is then left in the house, but, somebody thought that was ok... Brilliant. Oh, and this fan assembly is all preassembled, so its not like I stuck it together wrong.Fact is, I don't see what they need these resistors for to begin with. There's no such parts on the burner control, and it runs cool as a cucumber.ReRouter,Yes, they do have an earth ground. Probably stole the idea. I'm surprised they didn't cut costs there too!

author: IanB
author_rank: Super Contributor
timestamp: April 09, 2012, 03:57:56 am
content: On the furnace/boiler thing: in industrial plant, the furnace is the bit of the system where the fuel is burnt to generate heat and boiler is the bit of the system where water is heated up or turned to steam. So both can certainly exist in the same plant. In domestic situations I guess the terminology is fairly loose, although normally a domestic boiler makes hot water and a domestic furnace makes hot air. I have not heard of a domestic unit that does both before .As to matters of substance, an industrial furnace would normally have automatic control of that damper ("gate") in the pipe leading to the exhaust fan, to keep the amount of negative pressure just right. Adjusting it manually is going to be tricky since I imagine the correct opening will vary with the season and the amount of wind outside. You seem to have a few pieces in your system that are not playing well together.

author: SeanB
author_rank: Super Contributor
timestamp: April 09, 2012, 08:24:26 am
content: Fixing the board will be better, I did that 15 years ago to a fan controller ( was not going to buy a new board if it would fail again, and it was bloody expensive as well) using 10W wirewound resistors in place of the 0.5W units that ran so crispy hot. 2 new resistors and a new zener diode and capacitor ( zener was cooked by resistor till it went short, and capacitor was brown and bulging for the same reason) shoehorned into the din housing and it is still running, now on it's second contactor ( old one wore out from use) and going strong.Those resistors are so hot because the board is set for 120VAC power, if you used a 24 VAC transformer and set the board to run on 24VAC then it will run cooler. You might need one or two extra relays but they will be cheap, and the transformer is likely already there in the furnace controller to provide power to the thermostat.

author: amyk
author_rank: Super Contributor
timestamp: April 09, 2012, 08:45:43 am
content: What are those resistors for? The fact that I can see one trace from them going to the input of a bridge rectifier makes me think they were too cheap to use a proper PSU and used a resistive divider insteadAt least they could've used a capacitive dropper.

author: SeanB
author_rank: Super Contributor
timestamp: April 09, 2012, 09:07:46 am
content: Class X capacitor costs more than the resistors, and would need the 2 resistors in any case to pass UL cert. Those look like fusible resistors in any case. The 2 next to each other are the power dropper, the other is a drive to the optocoupler, they probably really designed it to work off 24VAC, but at 130VAC it still is within the opto max current ( probably barely or just above but the opto will survive for a while before crisping) so they did not change anything. It would work better with a 24VAC supply from the thermostat transformer.

author: BBQdChips
author_rank: Contributor
timestamp: April 09, 2012, 01:37:37 pm
content: Don't all fusables have a fifth color band? I could be mistaken, I don't use them often.I asked why they were there as a rhetorical question really. I know whattheyput them in for, I just think the whole thing is very crude, and there most certainly are easy, safe, solutions to all the incredibly simple design considerations of such a board. Fundamentally,it's two relays and a switch. 555 not withstanding...Where safety is concerned, they could have just as easily checked for an overcurrent situation on the motor to see a stalled rotor condition, as use the vacuum switch. Especially since it samples the wrong place anyway. If current limiting was an issue, they make SCR's prit-near every day.Ian, I'd be scared of any servo control these yeahoos would put on a damper. And, I didn't use the "damper" term because to me that implies something active. Even if only barometric. This thing you set by loosening a screw, move it and tighten. And never see again.

author: Rerouter
author_rank: Super Contributor
timestamp: April 10, 2012, 08:43:03 am
content: the fun world of 1930's engineeringso have you made any attempts to fix it, or will you just straight out rebuild it?

author: vk6zgo
author_rank: Super Contributor
timestamp: April 10, 2012, 09:15:00 am
content: Quote from: Rerouter on April 10, 2012, 08:43:03 amIf it was 1930s engineering,it would work for the next 40 years!

author: Rerouter
author_rank: Super Contributor
timestamp: April 10, 2012, 11:48:00 am
content: true, but not when its made of the same designs from the 1930's but with todays cost cutting and underspeccing

author: BBQdChips
author_rank: Contributor
timestamp: April 10, 2012, 01:11:00 pm
content: Quote from: Rerouter on April 10, 2012, 08:43:03 amFor now, no, I just added some new stack pipe and ran the exhaust up the chimney. And re-adjusted the air intake then of course. I spent from 1:00-7:00 Easter Sunday trying to figure out what was going on with it and wasn't in the mood to spend another minute. Thing is, by all outward appearance, everything worked perfectly. It fired up, flame looked great, stack temp was good, and it might run for a day. So, sitting there staring at it attempting to figure out when it was going to stop, and why, wasn't on my shortlist of things to do. Sunday, I had seen it stop even when I was looking right in the sight door, and everything I could see looked great. BUT, cleaning the fuel line had appeared to make it work for 3 weeks, so, while I didn't want to believe dirt was the trouble, or fuel starvation, strong evidence was showing me wrong. And the last time the vent control died, it just up and died. With the venter turning on and appearing to work, I thought I was looking at a burner control problem, or some sensor issue. And, the burner control is one of those that's poured with resin all over the boards, so testing there is pretty much out of the question too.The last two days, it's been so nice to get up, go turn on the shower, and have warm water come out! I bet most of you take such things for granted?I would like to make a new one from scratch. I do think it's more efficient than using the chimney, especially in winter. An active damper would also be a nice addition.