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Old 12-19-2016
Debugjaws Debugjaws is offline
Senior Member
Join Date: Jun 2016
Location: Newberg
Posts: 194

Hi Ned,

It sounds like you're getting ready to make the change over. My system is not a school bus model. It's a DBW2010.

Two pumps was easy. I bought my boiler from Rick Shawver. It came with a super cool case which had a Hella pump as part of the assembly already mounted. It was set up to take or "pull" from the return line and pump it through the boiler then back up into the coach on the feed lines. Since Primus used two pumps, I felt it a good idea to add the second given the amount of volume and distance the fluid needs to travel. I bought a duplicate pump off of ebay and mounted it to the rear wall of the aforementioned case. It "pushes" the fluid upon exit from the Webasto through the feed lines back into the coach.

I also changed out the two Primus plastic over-flow tanks to a single, 3x larger over-flow tank made out of stainless (see pic). Balancing the small tanks was kind of difficult. Given that the system went from two completely separate zones to one large controlled zone there is some engineering work to be done to figure out exact rates of flow, expansion, return, etc., that frankly I'm not smart enough to do. After speaking with some others on the WOG I decided to go to the single larger tank and eliminate the balancing act altogether. I was sold on this idea after spending Thanksgiving weekend balancing the two out.

I also replaced the original snap discs that fire the fans on the convectors. I bought adjustables that range from 90 - 130 degrees. It was worth the piece of mind.

Originally Posted by nbedinger View Post
Gerry, I agree with Rick, thanks for the great write-up on your clean and versatile installation. I am particularly interested in your new 2-into-1 plumbing design, the valving for adjustable flow is intriguing, but I will definitely borrow the two pump design--a pusher AND a puller is bound to do good things for heat circulation.

Good luck with diesel heat. Is it a schoolbus heater model?
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Gerry Lefebvre
Newberg, Oregon
91 WB 40'
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