Normally I'd post this in the residential section, but the technology is probably more correctly placed here.
Background: Trying to get a hot/cold water HVAC for our residence. Contractors doing this residential are few and far between. Most (all?) want an engineer to do the design. Which in turn requires knowing enough to explain to the engineer what you want. To get an engineer to do it from scratch, and do the cost/benefit evaluations would cost more than the system!
System: Probably 1 mod-con boiler with outdoor reset or 0-10v input, 1 or 2 chillers (for this discussion assume one modulating chiller with load reset or 0-10v input), and 4 zoned air handlers with an ECM or VFD controlled blower motor and hot and cold water coils. The first and second floor are separated because the structure forces different ducting systems; large radiant heat loads dictate the east/west zoning.
Objectives: Efficient temperature and humidity control with reheat dehumidification if called for. There doesn't appear to be anyway an economizer can be cost justified in this application. IAQ may need circulation and activation for steam humidifiers and filtration.
The T7351 seems to have lots of these features.
•Typically used in buildings (including:restaurants, shopping malls, office buildings and banks) under 55,000 square feet.
•For single zone rooftop units, split systems, heat pumps or hot/chilled water systems.
•7-day programming.
•Two Occupied and two Not Occupied periods per day.
•Keypad multi-level lockout available with all models.
•Individual heat and cool setpoints available for Occupied and Not Occupied periods.
•Intelligent Fan™ feature energizes fan continuously in the Occupied periods. Fan can also be configured for conventional heat or electric heat fan operation.
•Remote sensor capability for temperature (including outdoor air and discharge air) and humidity sensors.
•Recovery ramping control automatically optimizes equipment start times based on building load.
•Auxiliary subbase contact typically interface with a Honeywell Economizer System (for total rooftop control integration) or act as dehumidification output.
Questions
Is it a current model? Is it reliable? Are their better ways to gain the same or more functionality while keeping the cost down? iWorks and Uponor are nice, but a bit out of the price range. If you can buy a new car for the price of the controls, definitely out of the price range!
Can the T7351 be zoned? That is, could a T7351 be used in each zone and some how the multiple cooling/heat stages be used to drive the system? If the boiler uses an outdoor reset and the chiller uses a load reset, could they some how be connected and use the stages to change the water flow rate? Would a more sophisticated system be able to control the water flow rate more precisely?
If we got this far and it might work, would it work with two staged chillers?
To make this work would each zone need its own pump?
Installed many T7300 series t-stats during the 90's. Always were on package and split DX systems. Might want to look into small zoning system that will incorporate your reset and stitic pressure control for fans...
Linear Mode
