Ro recuirc loop affecting feed pressure

[jake1]

I've got a home built unit with a procon 330 and 3 filmtec 4040's in series. Its been a great unit for concentrating my 1% birch sap to about 5-6%. I added a recuirc loop this year to try to help keep up with my evapo. I teed off just before my concentrate valve and added a 1\2" needle valve, then through a flow meter and down to the feed line of my procon. My normal feed pressure is around 45-50psi from a 3\4 hp flotec jet pump. So my concern is that when Im running at normal pressure "225psi" and crack my recuirc loop to around 2 gpm It increases my feed pressure to 55-60psi and seems to put back pressure on my feed pump and filter, im curious to know if anyone has some input. It tees in half way between my filter and procon inlet. I could get it a bit closer to the pump but I'm not sure that would help. Also does anyone know the feed pressure limits of a proven 330? I know min 20 psi but is there a maximum? Seems to me that it should be ok to put 60psi or more feed pressure but not positive.
Thanks for the advice,
Jake

[darkmachine]

How does your flow meter work on your recirc loop? do you have a one way valve on it? I considered adding one but i wondered how it would work with the potential for pressure going both ways(without a one way valve) I would like to know the recirc rate, but it doesn't really affect the operation, i just fiddle with the two needle valves...open recirc a little, close concentrate a little, repeat, until i'm getting at least 4%. My best guess is that as long as the feed pressure doesn't excede the output pressure it would be fine. I worried about the back pressure on my feed pump, i actually had to bypass the pressure switch on it to keep it from cutting on and off.

[jake1]

The flow meter doesn't have a check valve but it only reads one flow direction, its flowing correctly.

[Bricklayer]

What is the size of the line from your filter to the procon?
I have a 1” line from my filter to the high pressure pump. At the pump I have a T with the recirc 1/2” comming to that T as well as the feed line from the filter. Don’t have any issues.
After your needle valve you should not have much pressure. It shouldn’t be adding to your feed pressure.

[jake1]

3\4" feed line, 1\2" recuirc. When I get to 1.5 or 2 gpm on the recuirc it starts to up the feed pressure.

[Bricklayer]

I wouldn’t worry about that. 60 psi feed pressure into a procon should be fine. I’m sure there is literature somewhere stating the exact amount it can handle. But I’m sure it’s well over 60 or 70 psi.
What about your overall system pressure. How does the main system pressure react when you have your recirc wide open and you have your concentrate valve set at 225. Close the recirc slowley. Does your main system pressure go up or down. It should go up.