Hydro Air short cycle?

budalb

I have a hydronic system with 3 zones of baseboards and one zone of hydro air. I recently have a condensing boiler installed with outdoor reset. The hydro air system always cycle more frequent than baseboard loops. At this time of northeast, it will be on for 4-5 mins and off for 8-9 mins, and repeat. The baseboard loops will be always on for hours.

I guess I need to balance the system. How do I do it? Restrict the flow to the hydro air loop?

Thanks

STEVEusaPA

Need to know more about the controls.
Ideally, when the hydro zone calls, the control should reset the boiler to a higher temperature, like it does for DHW. So the outdoor reset is working against you.
It's not seeing hot enough supply water temp to keep the fan running.

mattmia2

Does it heat the space adequately? It might make more sense to slow the blower speed or run the blower off a timer from the t-stat rather than off an aqua stat if it has adequate output at the reset temp.

budalb

The boiler is Uitca MACF-150 (combi). My understanding is: the thermostat call is connected to a TACO 4-zone zone valve controller, which then is connected to the boiler control terminals. When heat is called, the boiler starts up and the primary circulator (built-in in the boiler) starts. Then the secondary circulator starts.

The heating side set point is controlled by the outdoor sensor. I read the supply temp at ~120F. The dhw is not controlled by the outdoor sensor.

I suspect that the hydro air system has higher heat output, so that the room temp is satisfied earlier than the baseboards. Can I just partially close the valve to the hydro air loop? any down sides?

STEVEusaPA said:

Need to know more about the controls.
Ideally, when the hydro zone calls, the control should reset the boiler to a higher temperature, like it does for DHW. So the outdoor reset is working against you.
It's not seeing hot enough supply water temp to keep the fan running.

budalb

Yes. It heats adequately. It satisfies the same thermostat set temp a lot quicker than the baseboard loops. Slow down the blower may be a good idea, even though I don't know how to do it. I guess I need to reduce the heat output of this loop so that it matches other loops. I am thinking about restricting the flow to that loop.

mattmia2 said:

Does it heat the space adequately? It might make more sense to slow the blower speed or run the blower off a timer from the t-stat rather than off an aqua stat if it has adequate output at the reset temp.

pecmsg

The hydro coil has a huge BTU output so some regulating of the air temp is needed. Slowing the fan, limiting the water temp in and or out.
Taco speed drive pump measuring return water is good for that.

budalb

Limiting water temp is not feasible. I have one boiler, so the supply water temp is the same for all zones. I will look into slowing down the fan. Are there any disadvantages of reducing the water flow rate? I can easily do it by turning the valve. Does it hurt the secondary circulator (TACO 0015E3 3-speed)?

pecmsg said:

The hydro coil has a huge BTU output so some regulating of the air temp is needed. Slowing the fan, limiting the water temp in and or out.
Taco speed drive pump measuring return water is good for that.

Big Ed_4

You would be better off controlling the air flow . Most air handlers use mutable speed blowers. . Normally Heat would be half the CFM's of AC ...

mattmia2

if you reduce the water temp/flow too much without reducing the airflow, it will feel cold and drafty.

budalb

Thanks for the advise. I am not quite comfortable of adjusting the blower by myself. Need to find the manual of the unit.

Big Ed_4 said:

You would be better off controlling the air flow . Most air handlers use mutable speed blowers. . Normally Heat would be half the CFM's of AC ...

HVACNUT

What controls the fan in heat mode? The thermostat, aquastat, relay, sequencer?

budalb

Very good point. Thanks

mattmia2 said:

if you reduce the water temp/flow too much without reducing the airflow, it will feel cold and drafty.

pecmsg

budalb said:

Limiting water temp is not feasible. I have one boiler, so the supply water temp is the same for all zones. I will look into slowing down the fan. Are there any disadvantages of reducing the water flow rate? I can easily do it by turning the valve. Does it hurt the secondary circulator (TACO 0015E3 3-speed)?

pecmsg said:

The hydro coil has a huge BTU output so some regulating of the air temp is needed. Slowing the fan, limiting the water temp in and or out.
Taco speed drive pump measuring return water is good for that.

TACO Viridian for that circuit!

budalb

The fan is controlled by thermostat, as I know. I don't know the details of control inside the hydro air unit.

HVACNUT said:

What controls the fan in heat mode? The thermostat, aquastat, relay, sequencer?