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How to bleed in-floor loops?
Converting the electric-heated part of my house over to hydronic. Looking at installing underfloor heat plates with 1/2" Al-PEX 8" OC fed from a manifold with actuators. Have worked my way through the entire Siggy book and have done heat loss calcs for all rooms.
One of the smallest loops would have a tube length (including leader) of 186 ft, flow rate 0.6gpm at 26F, supply temp 117F for 10F delta-T. Heat output 2,000 btu/h, matching heat calc.
A bathroom would be even smaller: 100 ft of tube in-floor, 0.2gpm (0.32 fps), 1,000 btu/h.
Lochinvar WHN-055 with Grundfos Alpha circulator directly feeding a manifold. Whole-house heat loss of 22,000 btu/h.
At 0.6gpm, this 1/2" PEX loop would have a water velocity of only 1fps, making me think that it would be prone to air locking (not in the range of 2-4 fps).
Given that the loops would be above the level of the boiler and manifold, how do people incorporate an air-bleed mechanism for such an under-floor loop?? The water velocity is too low to entrain air bubbles and bring them back to a central Air Separator and the floor is in the way of putting a bleed valve at the high point.