A puzzler

LilJoe

Firstly...I've been lurking this site for a long while and am amazed at the wealth of knowledge here. I've got 20+ years in the trade and cant believe how little I know.

I have a situation that I can't figure out.

 This week I installed a 3 zone system on an existing furnace using a Robertshaw Simline Classic zone control (I've used this dozens of times with great success).



All went well until the customer called me and said that the furnace

was overshooting the t-stats by 2 or 3 degrees.This was unusual. I spent

a couple of hrs observing and was surprised to see a 4-5 min fire after

the t-stat was satisfied.(I disconnected everything, jumped R & W, fired the burners,

removed the jumper....gas valve remained open). I called York tech

support and was told that it was either a sticky gas valve or faulty

board. Tested the gas valve, OK. Board is doing everything as asked so

it seems OK. (I don't always trust Tech support but that's another story)





After further online research I fount this info @ Johnston controls{York}:







"York MODELS: PC9*DH



UNLIKE CONVENTIONAL SYSTEMS, THE



WALL THERMOSTAT DOES NOT SIMPLY TURN THE FURNACE ON



AND OFF. THE FURNACE CONTROL CALCULATES THE DEMAND



AND MAY CONTINUE TO FIRE THE FURNACE DURING PORTIONS



OF THE THERMOSTAT "OFF" CYCLE"





I said to myself "what the heck" now I have a perfectly good zone system and a perfectly good furnace that wont co-operate.





Any suggestions as to how to remedy the problem?

Tim McElwain

I would suggest

getting in touch with York to make sure all your controls are compatible with the York integrated control package.

John Mills_5

Modulating furnace

York's modulating furnaces do ignore the thermostat at times continuing to run at a very low firing rate. That's their way of modulating with a single stage stat. The board guesses that you will still need a little heat even if the stat is happy.



There is a zone setting on the board. Not sure what all it does but it is for using that modulating furnace and zoning. If you can't get help here, there's another forum where there are some sharp York guys.

Tim McElwain

Lil joe,

if you could possibly get me the number of the board and the make in the blower compartment of the furnace I will be able to help you out.

LilJoe

Still workin on it

I had to abandon this project for a day or 2. I will get back asap to get you some #s  sir.



I left the system running on 1 stat and as the zones default open, it works OK.



I  find it odd that when the furnace fires on a no heat call it will overshoot the stat by 3-4 degrees. The owner said he noticed this occasionally in the past but never gave it much thought.



I'm the guy who dropped the ball by not researching the furnace further before installing the new duct and zone system. Its just not something I would have ever expected to come across.



THX joe

LilJoe

Sorry

I didn't get back here sooner. I spent some time over a coffee with a couple of York guys in my area and finally got this sorted out. There's a DIP switch on the main circuit board that is supposed to be labeled "ZONE-YES/NO". Well the switch was there but the wording was not. Works like it was designed to now.  Thanks 



Joe

Tim McElwain

Lil Joe, That is why

I was asking the number on the board so I could determine if it had special setting well anyway you got it figured out.