You have been called to help solve some comfort issues on a new large custom home. When you arrive you see there are five zones of heating. Zones 1, 3 and 5 are air handler zones with A/C. Zones 2 and 4 are infloor heating zones (for comfort only). The owners say that most of the winter everything is comfortable and working fine, however, when it gets really cold the house always seems to be a little cooler than they would like, and the boilers seem to come on and off a lot. The boilers and the gas piping are correct. The venting is correct. And all safeties and settings are correct. Based on the information on the rating plates, the air handlers are sized correctly.

BASED ON THIS INFORMATION:

1. You start at the boilers and they are piped correctly, or are they? The boilers are piped with 1-1/4” pipe and then tie into 1-1/2” pipe out to the 5 zones and back. What size piping would you choose?

1. 1-1/4” to the 1-1/2” is fine. This is not the issue.
2. It all should be piped with 1-1/2”, including the boilers.
3. It should be piped with reverse-return on the boilers.
4. The boiler piping is fine, but the main piping should be 2”.
5. None of the above.

2. Zone 1 is a 70,000 BTUH air handler and has 1” supply/return piping. You do the math and decide:

1. Everything is fine with this zone.
2. To change the piping to 3/4" because the fittings on the A/H are only 3/4".
3. You purge the unit, just in case there is still air trapped in the coils.
4. To add an air vent by the A/H, located in the attic, just in case it is an air problem

3. Zone 3 checks out fine but you do the math and decide that:

1. It is ok as the A/H fittings are 3/4" and it is piped with 1”.
2. The piping should be 1-1/4”.
3. You check for air but don’t get any.
4. The pump isn’t matched to the BTUHs, so you suggest a larger pump.

4. Zones 2 and 4 are doing the infloor and everything seems fine. When running, there is a 20-degree delta T on both zones, and the rooms never seem to be a problem. This is because:

1. A 20-degree delta is correct for all infloor heating jobs.
2. They are connected with 3/4" supply/return piping, which is fine based on the inputs required.
3. You could have piped this with 1/2" supply/return based on the BTUHs required.
4. The manifold connections are 1”, so it should have been piped with 1”.

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