I have a new York 4 ton 15 SEER heat pump with 5 ton York air handler with expansion valve; it also has a coil behind the air handler going into supply line from an outside wood boiler.

I think the fan motor is 1 hp variable speed motor, 1050 rpm. I don't think it blows enough air out the vents.

With the boiler water temp outside at 160 degrees, it took from 9:30 to 12:00 (2.5 hours) to bring the inside temp from 57 to 62 degrees.


  • Outside temp was 46 degrees.
  • It is a 2400 sq.ft. heated space.
  • Walls are foamed 1/2", with 6" insulation.
  • Ceiling has 12" insulation.

Can I get a higher rpm motor to turn the fan faster to ultimately solve this problem, or is the boiler coil reducing the air flow too much?

If not, what do you think the problem is? I asked the HVAC contractor who installed it but they are not helping.

If you need more information please ask.

  • 1
    First make sure all the filters are clean. Do you have good airflow coming from the registers? That is way to long something is definitely wrong. What is the delta T across the boiler coil?
    – Paul Logan
    Feb 3, 2018 at 7:08

1 Answer 1


If the blower motor is actually a 1 HP motor it should be able to provide sufficient air delivery through the system. Do you know what speed the motor is utilizing, (most have 4 speeds).

The coil design and the resistance of each coil will play a major roll in air flow as will the size of the supply and return ductwork. A lot of contractors use a high resistance figure when sizing ductwork in order to save a few dollars.

This results in a lower delivered air flow, along with more air noise. With the information you have provided it will be very hard to offer any solutions. There are some pretty smart guys that monitor this site so more info is needed, such as the model number of the equipment including the heat coil specs, size of the supply and return duct work, type of filters used, etc.

By the way, if the water delivery temperature was 160 degrees at the boiler, that is not very hot when trying to raise the house temperature quickly. You also need to check the temperature drop across the coil, the in and out temperature of the water and the air temperature increase across the coil.

Raising the water temperature to say 180-200 degrees will greatly increase the output of the coil. The best answers would be provided by someone actually being at your location.

Hope this helps.

  • The difference between 160 and 180+, is it talking too long. +1
    – Mazura
    Jan 20, 2019 at 13:20

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.