Radiant Heat Balancing/Wirsbo Manifold Configuration

Old 11-19-19, 05:46 PM
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Radiant Heat Balancing/Wirsbo Manifold Configuration

I have a question about our residential radiant-heating system. We have two zones configured for radiant heat – the kitchen (first floor) and master bathroom (second floor). The kitchen loop is much shorter than the bathroom line. The rest of the home operates on forced hot-water radiators (separate feeds from boiler). The furnace is a Trio PurePro boiler and there is one Grundfos pump that services all HW lines. We have been here a few years and the radiant heat was installed by the previous owner. I have included pictures of the boiler and radiant-heat manifold. We live in the northeast (US) so in the winter the temps can get very cold. House built in ~ 1976 and appears to be fairly well insulated.

The kitchen floor seems to warm up fine, the upstairs bathroom is slower to respond and generally does not get as warm as the kitchen. There is one thermostat in the kitchen that controls the two zones and both are activated when calling for heat. I don’t know anything about the amount of insulation installed in the upstairs bathroom floor.

The radiant hot water is distributed by a Wirsbo brass manifold with manually-operated balancing valves. Each zone (kitchen, bathroom) is set up on a separate 2-port manifold. For each zone, the supply line runs out to the floor and the control valves are located on the return side. A piece of PEX tubing runs between the supply and return line on the second port of each manifold. Both manifolds (kitchen, bathroom) are configured similarly. The picture only shows one of the manifolds.

We have been trying to balance the flow to ensure the bathroom floor is warm enough, especially important since cold weather is coming. The return line is hot when the thermostat is calling for heat and the flow is ~2-3 gpm (as per the meter on the Grundfos pump) for both zones. I flushed out the lines last year and don’t believe there is air trapped in the system. The manifolds do not have flow meters or temp gauges.

I have attached photos of the boiler/piping, the radiant heat manifold, a diagram of the HW feed/return, and a diagram of the Wirsbo manifold (2 installed, only one shown).

My questions:

1. Is there any reason for the ‘PEX jumper’ between the supply and return line? Can these ports just be capped off? I have tried to close down the adjusting valve to prevent flow in this line but not sure how tight it is. I don’t want to muck around with the valve cartridges as replacements are no longer available. Perhaps it’s just a by-pass line but not sure how it would be used, or if even needed.

2. We have a programmable thermostat and lower the temp during the day and raise it at night. For radiant heating systems, do folks generally set the temperature and forget it or can it be adjusted for day/night? I understand it takes longer to heart up these systems so perhaps it should be set at temp and left alone.

3. Given that the manifold is an older style unit, is there another type that would easily replace this one that would require minimal re-plumbing? There’s not a lot of play in the PEX lines so any replacement should be similar in size/dimensions to the original. It would be helpful if a new manifold had flow meters and/or temp gauges to assist with balancing.

4. Can PEX lines be connected/disconnected (they have a threaded fitting, R20) or is it a one-shot deal such that they that cannot be removed without damaging the o-ring/ferrule?

Thanks in advance for any help/advice you can provide.

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