All right, so some of you have probably seen my reciprocating compressor, cutaway video and just so you're aware that was completely coincidental that it ended up being a Bristol t8 series, which is the compressor that unloads one of these cylinders, one of the Pistons when it runs In the opposite direction, so when it runs one way it pumps both Pistons when it runs the other way, it only pumps one and it turned out great because it's one of the most interesting compressors ever made. In my opinion, in residential, it's had a lot of issues. There was a, I don't want to say a recall, but there was a accommodations made by carrier been a lot of issues with it and the one I pulled apart. It had a burn start winding and didn't appear to have anything else significantly wrong with it, but it's a very interesting thing that they've done, and so I want to use this opportunity to talk about how its wired.

So if you look at this schematic, so we've got a an actual schematic diagram over here and then we have a connection diagram which actually shows how it's wired in real life. So the two things I want to point out this is CH. This is a contactor hi. So if you look down here, you can see it says that contactor high-capacity 24 volt, coil and contactor local asset II, 24 volt coils.

So that's gon na be what we're focused here. So you'll notice. The high-capacity contactor has a contact point on it, and it also has a it's like a plus one contactor. So it just has a straight through a connection that doesn't make a break, so l2 is constantly connected, and then you have a contact and then with the low capacity contact, or you just have a contact.

Let's go through and show how this is wired, because it's actually pretty simple but first thing: you'll notice is that the start capacitor and the start relay as well as the compressor capacitor are connected in between these high and low. So that's kind of strange right, but then the next thing you'll notice, is that both high and low both connect at the same point. They both connect to l1. If you have high contactor, is pulled in then you're going to have current.

That moves through here. Moves through like a traditional start relay, so you go through your. You start start relay in typical kind of wiring configuration here, five to one wiring configuration and then it goes through and feeds through to the start winding. That's when this one is closed and this one is open now, if they're both closed well, then it doesn't work.

So if this is set up, so the only one closes and that's something that makes it different, at least on the high voltage side from a traditional multistage unit and a traditional multistage unit, we think are a you have y1 call and a y2 call. That's still true here on the low-voltage side, but you do not have you cannot have both of these contactors pulled in at the same time. Otherwise it's definitely not going to function properly. So, in order to have a potential difference from this side to this side, one has to be closed and one has to be open.

So in low stage it's gon na be this one's closed and this one's open in high stage. This one is going to be closed and this one's gon na be open, but you're gon na notice. Here, what actually occurs, because this is a subject that comes up often and debate is: can you run a single phase motor backwards and this compressor kind of proves it? Whether or not that's the reason why they had so many failures or not? That's a whole. Another question that I am not qualified to answer, because I'm not an engineer, but what they're actually doing is they're swapping run and start undisputedly, they're, swapping run and start, and so, when you're in high stage then run is this winding run is typical and then start Is fed through the capacitors or not stop fed through, because you know I have talked about this and multiple podcasts and videos that you can't feed through a capacitor.

But it's it's the other other side from the capacitor of run and then when it goes into low stage instead of high stage. This one opens, and now it comes through this direction and now you're feeding start the start side with a line with l1 and then you're feeding run now with the opposite side of the capacitor. So it's just a very interesting setup there and I'm trying to figure out. I haven't actually it's funny because I haven't actually even thought about this start relay.

Let's think about I'm thinking about this with you in real time here. So now you have this start relay and it's going to be made through here until there's a path yeah, so it'll work either way yeah. So both the start and the end, the run capacitors are going to be in the circuit in both high and low. Let's the wire this way so anyway, I thought it was pretty interesting if you really good at reading where died wearing diagrams.

This might be a little bit confusing to see, but but if you have a little bit of experience, it'll it'll make a lot of sense, depending on which one which contactors pulled in that dictates, which winding, where the run or start is fed by line and then Which other side is fed by the opposite side of the capacitor, so you essentially are flipping start and run, which has a lot of interesting ramifications, because we've always of course been taught. That start has a higher resistance than run. So, what's that going to do you know is, is the start winding really designed to be carrying that constant current that you would normally see on run a lot of interesting questions, questions I don't necessarily have answers to, but that is how it works, and that is Why it runs in one direction in high speed where it engages both of the cylinders and then another direction at low speed when it only engages one all so, hopefully, you found that to be interesting, and that is the Bristol t8 series of compressors. This is specifically is a wiring diagram for a 38 yd B.

It's a order carrier two-stage heat pump. Alright, thanks for watching and we'll see you next time.