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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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Taco PC700-2 "boiler target temperature" displays "-------"

Customer Question

taco PC700-2 "boiler target temperature" displays "-------" shuts off boiler prematurely
Submitted: 8 months ago.
Category: HVAC
Expert:  Phil replied 8 months ago.

Hello, so far it sounds like the hot water radiators have a little air in them and that is slowing the water flow though the boiler, causing it over heat and go off on its high temperature limit switch.

Tell me a lot about your technical skills so that I coach you most effectively or tell me which direction you are from the center of the nearest town or city so I can locate the best rated local boiler service for you.

We can go from there

Customer: replied 8 months ago.
I have been working with industrial HVAC BMS for many years and am very familiar with my home hot water boiler controls. The boiler is not shutting off at high temp. The new Taco SR504-EXP-4 has been working well alone. I added the Taco PC700-2 to incorporate an Outdoor Temperature Reset. The PC700-2 display shows "- - -" for Boiler Target water temperature. I believe that is because it is not calculating the target boiler water temperature which results in the boiler not running as soon as I put the SR504 "Reset" mode into service. Trying to get it working this weekend and before I return it as defective. All adjustable settings are factory, as detailed in the PC700 Instruction sheet (PDF easily available online). Additionally, when I press the up button on the PC700, the boiler "On" indicator is displayed, it does not actually run the boiler as it should. Attached 102-389 is the PC700 instruction sheet.
Expert:  Phil replied 8 months ago.

Hello again, thanks for the response. It would be *you that has to input the boiler water set back temperatures... that cannot be nor should it be set at the factory. Why? because each system is different, boiler size and hot water flow and radiator capacity varies with each particular installation. Some systems will work well at low loads with a boiler water temperature of 120F, others due to inadequate radiator or coil capacity will have be set for a minimum 130F etc.... the factory cannot anticipate that requirement.

On this end, for the fee we charge I will not be able to do all that research and coaching for you, especially since you seem quite capable and have access to all of the relevant instructions.... just look for your options to set the reset temperatures,

I will opt out if you wish.

Customer: replied 8 months ago.
Boiler Target Water Temperature is supposed to be calculated by the controller. This value is not set, nor can it be set, by the user.
Expert:  Phil replied 8 months ago.

I will opt out and recommend that you discuss this with the TACO factory help desk.

Customer: replied 8 months ago.
Thank you for your time sir.