Stage 2: The Barn Loop
I have 1200 feet of mislabeled 1” inch Pex-Al pex from boiler to barn in 4 lengths (2 supply and 2 return). It is really ¾” Pex-Al pex. The interior dimension (I.D) of the Pex-Al pex is .806” (which is closer to 1” regular pex than it is to 3/4” regular pex.).So the run from boiler to barn is roughly a 300 foot one way ride. The four lines are wrapped in a heavy black plastic tubing, insulated to R22, wrapped in plastic tubing again, covered with aluminum roofing shaped in an inverted V, and buried on average 2 feet deep with no underground fittings.
The plan is to use a Grundfos 15-58 to push water out to the barn and another to push it back. The manifold is 1.25 black pipe, flanges are 1.25” too. In the manifold there’s a third Grundfos 15-58 to feed the 3 loops of ½” pex (each about 240 ft.)
The rooms in the barn are well insulated (R22 minimum but some is R50) but have cement floors. The radiant emitters are loops of ½” pex on the walls. There are 6 lines in 4 feet of height on walls 40 feet long. So the spacing is 8”. The temperature to maintain is 64*F.
According to calcs that I’ve done using formulae from the Manual of Modern Hydronics the emitters I have in place should be capable of 37-39 KBtus for each room. The rooms have excellent insulation (were it not for the floors). Anyway, the heat loads are a lot less than the capability of the emitters. I did my calculations based on 140* average water temperatures.
It is easy to calculate the head for a known pipe but what happens when you double-up the pipe (pex-al pex) as I have. Is it just by guess work that we arrive at a head calculation?
My main question is whether there is enough pumping capability in the plan.
Also, I’ve planned to have the two pumps (in the barn) operate on a thermostat, so that demand triggers flow. This feature could be eliminated and all 3 pumps could run full-time, if necessary.
The one pump, located at the boiler end of the barn loop would operate full-time. This boiler end pump (I hope) would prevent freeze-up in the event of a power failure; providing that it can push a minimal amount of water through the 600 foot barn loop.
In the event of power outage, the three 250’ loops would not have a dedicated driving pump so would be relying on the already heavily strained boiler-end pump. On the plus side, it should not take much flow of 140 degree water to prevent freezing.
The boiler end has a generator in case of power outage. The barn pumps do not have power in an outage.
Is there enough information here to assess the functionality of this loop?
I have 1200 feet of mislabeled 1” inch Pex-Al pex from boiler to barn in 4 lengths (2 supply and 2 return). It is really ¾” Pex-Al pex. The interior dimension (I.D) of the Pex-Al pex is .806” (which is closer to 1” regular pex than it is to 3/4” regular pex.).So the run from boiler to barn is roughly a 300 foot one way ride. The four lines are wrapped in a heavy black plastic tubing, insulated to R22, wrapped in plastic tubing again, covered with aluminum roofing shaped in an inverted V, and buried on average 2 feet deep with no underground fittings.
The plan is to use a Grundfos 15-58 to push water out to the barn and another to push it back. The manifold is 1.25 black pipe, flanges are 1.25” too. In the manifold there’s a third Grundfos 15-58 to feed the 3 loops of ½” pex (each about 240 ft.)
The rooms in the barn are well insulated (R22 minimum but some is R50) but have cement floors. The radiant emitters are loops of ½” pex on the walls. There are 6 lines in 4 feet of height on walls 40 feet long. So the spacing is 8”. The temperature to maintain is 64*F.
According to calcs that I’ve done using formulae from the Manual of Modern Hydronics the emitters I have in place should be capable of 37-39 KBtus for each room. The rooms have excellent insulation (were it not for the floors). Anyway, the heat loads are a lot less than the capability of the emitters. I did my calculations based on 140* average water temperatures.
It is easy to calculate the head for a known pipe but what happens when you double-up the pipe (pex-al pex) as I have. Is it just by guess work that we arrive at a head calculation?
My main question is whether there is enough pumping capability in the plan.
Also, I’ve planned to have the two pumps (in the barn) operate on a thermostat, so that demand triggers flow. This feature could be eliminated and all 3 pumps could run full-time, if necessary.
The one pump, located at the boiler end of the barn loop would operate full-time. This boiler end pump (I hope) would prevent freeze-up in the event of a power failure; providing that it can push a minimal amount of water through the 600 foot barn loop.
In the event of power outage, the three 250’ loops would not have a dedicated driving pump so would be relying on the already heavily strained boiler-end pump. On the plus side, it should not take much flow of 140 degree water to prevent freezing.
The boiler end has a generator in case of power outage. The barn pumps do not have power in an outage.
Is there enough information here to assess the functionality of this loop?
