Preheater darkening syrup?

[TunbridgeDave]

I'm embarrassed to say but I've always wondered why we have trouble making Fancy syrup on our rig and I'm wondering if it's the preheater. I've been searching now and then have found comments about how running copper preheaters dry can darken your syrup. Well, we have used an Small Brothers preheater on our 3x10 for 20 years and from time to time I have taken it off and been able to make very light syrup. How can this be? When using this preheater, every so often air burps out into the float box from it. For years I never really thought or worried about it. It originally had a small 1/4" breather tube soldered on top of the outlet pipe that never did anything, come to find out that it was soldered closed when it was made, so I cut it off (as it wasn't doing anything). Recently I've been looking at discussions about home-made preheaters and I noticed that on all of them, the sap enters from the bottom and exits the top. Well, mine is just the opposite. The sap enters the top and has to go back and forth four lengths of the preheater (7ft) going downhill all the way before it makes it's way to the float box. So I'm wondering was it made wrong when it was built? Should the sap be allowed to flow naturally uphill as it warms and will that help get rid of the air pockets? Or does the direction of flow not matter and do I just need to install a new breather?

[GramaCindy]

Just one question for you ….do you have a vapor escape? Not sure if that is the correct term.7452
But you can see the vapor escape on my preheater from Jim of Smokey Lake on the back right of the pic

[TapME]

Parallel flow pre heats are what we use. And yes your thought process is correct. The sap should be allowed to naturally flow uphill. U never want to have a vapor lock in it so a vent for that is a great idea. Steam is a powerful thing under pressure.

[TunbridgeDave]

I talked with Bascoms about the direction of flow, and they said they've seen them made both ways. As far as the "vapor escape" or vent, the breather tube I mentioned is for that purpose but it never worked. Also, it was put on the bottom pipe. I would think it would have been better on the top one since air bubble would rise to the top. I'm gonna fix the one that's there and maybe add a second one to the top pipe and see what happens.