This page is the working design plan for the Rixen MCS7 hydronic system. The kit inventory, official manuals, and source documents live on Rixen Hydronic Heat and Floor. The procedural install guide lives on Rixen Combined Installation Instructions. This page captures where components should go, why they should go there, and what needs to be verified before drilling, cutting, gluing, or tying into the Ford coolant system.
| Zone | Planned Components | Reasoning |
|---|---|---|
| Passenger-side interior plumbing bay | ComfortHot/expansion tank, main Rixen glycol pump, domestic hot water heat exchanger, domestic mixing valve, floor loop pump, floor loop mixing valve, air handler, MCS7 control box if packaging allows | Preferred Rixen service cluster. Keeps fill point, pumps, valves, domestic water, air handler, and service wiring together. Main glycol pump can sit near/below the ComfortHot tank so it is gravity-fed as Rixen requires. |
| Passenger-side underbody | Eberspaecher Hydronic S3 gasoline furnace, intake, exhaust, furnace coolant connections | Preferred furnace zone so the furnace stays close to the hydronic service bay and air handler. Must still clear gray tank/plumbing, doors, windows, exhaust/intake requirements, road debris, and service access. |
| Driver-side 31 gal aux fuel extension area | Furnace fuel pump | The van uses the Ford 31 gal / 115 L tank auxiliary fuel extension line on the driver side near the driver-side water/urine tank area. Mount pump close to the extension-line connection to keep suction side short, with inlet/big nut down, outlet up, and 15-35 degree angle. |
| Protected underbody fuel-line route | Fuel pump pressure-side line to passenger-side furnace | Rixen allows a longer pressure-side run than suction-side run, but the fuel line needs strong protection from heat, abrasion, road debris, sharp edges, moving parts, and service damage. |
| Near engine coolant tap points | Engine heat kit plate heat exchanger and Ford coolant branch connections | Use Rixen's engine-heat series loop from the dash exchanger outlet and Ford's permitted heater-hose area between the front cab heater and water-pump return inlet. Keep the Ford-side 5/8 in heater-hose loop short, protected, and minimal; let the Rixen glycol side take the longer run back to the house system. |
| Van floor | CNC heated floor, PEX, aluminum heat-transfer plates, aft passenger-side floor exit into plumbing area | Wait for Rixen's official floor piece map before adhesive. Dry-fit and photograph all small pieces first. |
Rixen explicitly shows the floor option as From Exp. Tank and Return to Exp. Tank. The diagram above represents that with a supply tee block and return tee block. Rixen's engine heat figure shows the engine heat plate exchanger in the MCS7 coolant circuit while the Ford engine coolant circuit stays separate; it does not show the engine heat exchanger as a separate from-tank/to-tank branch.
| Circuit | Official Kit Tee Count | What The Diagram Requires | Status |
|---|---|---|---|
| Floor heat option | 3 x P23-103 3/4 in barbed tees in the MCS7 floor heat kit |
Tee into supply from the expansion tank, tee into return to the expansion tank, and provide the floor mixing valve return/blend connection | Appears covered by floor kit. |
| Engine heat option | No tees listed in the engine heat kit; kit lists plate exchanger, bracket, barb fittings, elbows, clamps, molded elbow, and hose splice | Rixen shows the plate exchanger in the MCS7 coolant circuit, not as a separate tank tee branch | Do not reserve floor-kit tees for engine heat unless Rixen confirms a branch layout. |
| Main loop | No extra tee required by the basic loop | Tank supply to main pump, furnace, heat loads, and return to tank | Covered by MCS7 kit hose/fittings, subject to final packaging. |
For the engine heat kit, place the plate heat exchanger close to the Ford engine coolant tap points. Rixen shows the engine heat plate exchanger in the MCS7 coolant circuit, with the Ford engine coolant circuit remaining separated on the other side of the exchanger. The Ford coolant side should have the shortest practical hose runs, fewest joints, strong abrasion protection, and secure mounting. The Rixen glycol side can take the longer run back to the house hydronic system because it is easier to isolate, service, and repair without risking the drivetrain.
Practical implications:
62A Auxiliary Heater Prep.Keep the ComfortHot tank, main glycol pump, domestic hot water heat exchanger, domestic mixing valve, floor pump, floor mixing valve, and control box together in one serviceable passenger-side plumbing bay if space allows.
The main reason is the Rixen pump requirement: the main glycol pump should be gravity-fed from the ComfortHot tank because it can push but cannot pull. A grouped service bay also keeps fill, purge, isolation, leak checks, and electrical troubleshooting in one place.
The preferred architecture is to keep the ComfortHot tank, pumps, mixing valves, domestic hot water exchanger, air handler, control box, and furnace on the passenger side if packaging allows. This keeps the hydronic side compact and easier to service.
The tradeoff is fuel routing. The 31 gal auxiliary fuel extension line is driver side, so the Rixen fuel pump should stay driver side near that connection to keep suction-side length short. A protected pressure-side fuel line then routes to the passenger-side furnace.
The floor heat kit has its own glycol pump and mixing valve. The floor loop should be controllable from MCS7 and manually isolatable with service valves. This protects the summer hot-water use case: domestic hot water can be available without intentionally circulating through the radiant floor.
| Question | Current Answer | Needed Before Install |
|---|---|---|
| Exact furnace mount point | Preferred zone is passenger-side underbody near the hydronic service bay. Driver-side remains fallback if fuel/exhaust/packaging is better. | Crawl-space measurement against gray tank/plumbing, frame, tire, exhaust/intake path, doors/windows, fuel line route, and service clearances. |
| ComfortHot tank position | Passenger-side plumbing bay. | Confirm height, cabinet clearance, fill access, 120 V element access, and space below/near tank for gravity-fed pump. |
| Main glycol pump position | Near/below ComfortHot tank. | Confirm pump orientation and inlet always has flooded feed from tank. |
| Floor pump and mixing valve position | Passenger-side service bay preferred. | Confirm floor supply/return exit location and purge access. |
| Engine heat exchanger position | Near Ford heater-hose tap area, inline with the MCS7 coolant circuit. | Confirm safe bracket location and whether straight or 90 degree Ford-side plate-exchanger barbs package better. Hose size/fitting family is no longer a purchasing blocker. |
| Control box position | Passenger-side service bay preferred, near pumps and wiring. | Confirm harness lengths, 10 AWG power route, 12 V fuse panel route, and touchscreen route. |
| Air handler position | Passenger-side near plumbing bay, as far forward as practical in/near the galley zone. | Finalize duct path and return-air path to serve cab, middle seating area, and bedroom. |
| Floor exit | Aft passenger-side corner into plumbing area. | Wait for Rixen floor map and dry-fit floor pieces before adhesive. |
Baseline model assumption: Ford Transit 148 in wheelbase extended SRW cargo van. Ford lists the Long-EL body around 263.9 in overall length, 147.6-148 in wheelbase, 76 in rear overhang, 172.2 in cargo floor length behind the front row, 81.3 in body width excluding mirrors, and 54.8 in cargo width between SRW wheelhouses. Use these only for purchase planning; final hose and fuel-line lengths need a measured underbody route.
| Route | Estimate | Purchase Planning |
|---|---|---|
| 31 gal aux fuel extension line to driver-side fuel pump | 1-3 ft | Keep below Rixen's 6 ft suction-side limit. Ford BEMM says the 31 gal / 115 L extension line uses a lower female 5/16 in Gen 3 quick-connect; select the mating male fitting/reducer for the Rixen fuel line during mockup. |
| Driver-side fuel pump to passenger-side furnace | 8-14 ft typical; 16 ft conservative | Rixen includes 8 ft of 1/8 in fuel hose. Have 15-20 ft total available, but keep installed pressure-side run under Rixen's 21 ft limit. |
| ComfortHot/main pump to passenger-side furnace | 4-8 ft | Have about 10 ft of 3/4 in hose available for this local underbody drop/run. |
| Rixen glycol to engine heat exchanger and back | 24-36 ft total | Have about 30-40 ft of 3/4 in hose available for the two long protected Rixen-side runs. This is the reason the all-in hose estimate gets large; if engine heat is deferred, this hose can be bought later from measured routing. |
| Ford coolant tap to engine heat exchanger and back | 2-6 ft total | Buy 8 ft of 5/8 in heater hose as the practical quantity, or 10 ft with margin. Buy 12 ft only if the exchanger bracket location is unresolved and avoiding a second parts run matters. Also buy 8-12 x 22 mm spring clamps, 2 x 1/2 in MPT-to-5/8 in barbs, a 5/8 in bleeder, heat sleeve, matching Ford coolant, and bracket hardware. Final variable is straight-vs-90 fitting orientation and exact cut length. |
| Local service-bay hydronic hose | 8-15 ft total | Have 15 ft of 3/4 in hose for tank, tees, pumps, valves, DHW exchanger, and air handler; 20 ft is a comfort margin. |
| Floor exit to floor mixing valve/pump | 4-8 ft total | Columbia/JRD floor sheet says to leave 2 ft of 3/8 in PEX at the exit. Have transition fittings and up to 10 ft local plumbing allowance available. |
| Air handler to three vents | 16-24 ft total 3 in duct | The included 20 ft may work, but the cab outlet can make it tight. |
| Furnace exhaust | 3 ft likely enough if outlet is well placed; 5-6 ft practical upper planning range | Included 3 ft may be tight depending on safe outlet location, but Eberspaecher documentation supports keeping this run short. |
Keep the live blocker rows on Gaps and Questions. This page should retain only the Rixen-specific design and verification context that still matters before drilling, cutting, gluing, or tying into the Ford coolant system:
P11-400C pumps: one main system pump and one floor loop pump. Keep the kit-content record on Rixen Hydronic Heat and Floor.90 Ford-side barb orientation.MCS7 touchscreen and air-temperature-sensor locations.Resolved source-backed inputs that no longer belong in this live verification section:
TRN-Special-Notes.pdf on 2026-05-18.62A prep stubs, 5/8 in hose, 22 mm clamps, and the documented plate-exchanger barb/reducer path.2026-05-19 with the resolved Ford coolant tap method and 5/8 in Ford-side purchase basis.