Performance curves for TACO 0011-VDTF4 circulating pump

[bkspero]

My son's HVAC contractor has proposed that he replace his single speed boiler water circulation pump with a variable speed pump controlled by the delta T of the water across the hot water coils. They have quoted a TACO 0011-VDTF4 3 speed delta T pump.

Does anyone here have the performance curves for that pump? The TACO website has curves for the 0010 and 0012 models, but not the 0011. It does have a separate page for the 0011-VDTF4, but that page links to a data sheet with performance curves for their single speed pumps only. Online sellers offer that pump, but they, too, have data sheets for it which only contain curves for single speed pumps.

 

[Geofd]

Whats wrong with his single speed pump.

 

[bkspero]

Whats wrong with his single speed pump.

I don't know for certain. This variable speed pump is what the HVAC contractor quoted. The symptom is that the largest space heated by the boiler does not reach a comfortable setpoint on very cold days.

The boiler feeds hot water coils in two different heating zones (air handlers) plus a coil in a Triangle Tube indirect fired water heater. Each zone is controlled by its own zone valve. On cold days when both heating zones are calling for heat the water delta T across the larger zone coil is 40-50 degrees F (there was one reading of an 80 F delta T). The performance data for that hot water coil indicates delta T's there at max output should be about 20 degrees with 9 gpm of hot water flow (I could be wrong about the exact numbers, but it is much lower than he is seeing). During these times the boiler is running relatively short cycles to maintain the boiler water at its setpoint of 195 degrees F (that's as hot as he is comfortable running it). About 2-2.5 minutes burner on to reach the setpoint, then 3.5-4 minutes off.

They are planning, I think, to increase the water flow rate to the larger coil to increase its heat output and utilize more of the boiler capacity. But avoid having too high a circulation rate to a smaller zone when the other smaller zone and the larger heating zone are not calling for heat. At least that's my speculation.

Should the contractor be using a single speed pump? Maybe a larger one than the TACO 007 currently installed?

 

[Geofd]

If this has been a condition that's always been there. Was it sized correctly when installed????? How are your windows+wall insulation

 

[bkspero]

The house is a mid century modern type with heat loss problems due to both window and roof insulation deficiencies. The HVAC system was upgraded to heat pumps a couple of years ago by the prior occupants, but it was not sized properly for reasons that are too complicated to relate here. The boiler was to be used as aux heat.

My son has worked on its reconfiguration for the past 2 years and has now gotten it close to keeping the house at a comfortable temperature on all but the coldest days (primarily by setting the system to use the boiler as primary heat). His hope is that increasing water flow rate to the hot water coil in the larger zone air handler will increase the heat output to that zone and close the last shortfall. The HVAC contractor specc'd the subject pump for that purpose.

BTW, my son got in touch with TACO and was told by them that they did not have the partial power performance curves for the 0011-VDT pump.

 

[GReynolds929]

Are there balancing valves or flow control between the two AH coils?

 

[bkspero]

Each hot water loop branches off the main supply line to 3 valves. In order, a ball valve, a Honeywell zone control valve (I have a photo of 1 showing a model #V8043E1012), and a manual gate valve.

I believe the zone control valve is only on-off, so the answer to your question is, I think, no. Unless the manual gate valves can provide dynamic balancing in a way I don't see.