Taco PC700-2 boiler reset


  #1  
Old 12-09-11, 01:20 PM
B
Member
Thread Starter
Join Date: Jun 2007
Location: NYC
Posts: 236
Received 0 Upvotes on 0 Posts
Taco PC700-2 boiler reset

I have a taco pc700-2 plugged into a taco SR 504 EXP running my hot water boiler,with BB hot water heat.Not sure if it is working right or not.My settings are---Boiler start-70---outdoor 70--boiler design 180 (have boiler set for max 185 before shut off,have PEX in whole system) ---outdoor design 5----boiler min 145----diff Ad ----wwsd off.I don't understand that if the pc700-2 panel says boiler target is 145 why does the boiler go off at 172 on the panel.This was when the outside temp was 34.Other times out side temp was 50 and boiler target was 145 and it went off at 172. Maybe I do not understand what boiler target means.
 
  #2  
Old 12-09-11, 03:54 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 19,710
Upvotes: 0
Received 8 Upvotes on 6 Posts
Your settings all appear correct.

(except for possibly the outdoor design temp. I believe NYC is 10°... but this should not cause what you are seeing)

Do you have the switch in the 504 on RESET?

Do you have an indirect water heater on the system?

How long has the 700 been connected and operating? They need a little time to 'learn'. The AUTO DIFF in particular... perhaps the control is still 'adjusting' the diff? To learn if this is the cause, you could set the DIFF to manual, and use say 20° for a while and observe.

Remember that every time you make changes to the setting, the control needs to 're-learn' the building and boiler.

Does the boiler temperature gauge agree with the reading on the 700 display?
 
  #3  
Old 12-09-11, 04:22 PM
ItsTim's Avatar
Member
Join Date: Nov 2011
Location: God Bless America
Posts: 112
Upvotes: 0
Received 0 Upvotes on 0 Posts
Auto differential (Ad) may have something to do with it. The boiler will shut off when it is (differential/2) ABOVE the target temp.

Granted that would be a 54 degree diff, but it may contribute to what you're seeing.

172 is the temp when the boiler actually stops firing?
 
  #4  
Old 12-09-11, 04:35 PM
NJT's Avatar
NJT
NJT is offline
Member
Join Date: Oct 2006
Location: USA
Posts: 19,710
Upvotes: 0
Received 8 Upvotes on 6 Posts
172 is the temp when the boiler actually stops firing?
I think I know where yer going with this Tim...

Bill, if you are reading this temperature some time AFTER the pump has shut down, it could be due to something called 'heat soak'.

You did say:

boiler target was 145 and it went off at 172
So I think you took that reading at the moment the burner cut off... but, in case not,

Boiler water temperature can INCREASE significantly AFTER the circulator shuts off, because the heat that is trapped in the cast iron transfers to the boiler water.
 
  #5  
Old 12-09-11, 05:52 PM
X
Member
Join Date: Nov 2005
Location: USA
Posts: 2,338
Upvotes: 0
Received 0 Upvotes on 0 Posts
As said earlier, set diff to 20 and leave it for a week or three. It should settle in pretty well.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: