Do I need a new transformer?

Pat_32

Installed a new honeywell ct87k heat only thermostat and will not work. Tested wires getting 36.7volts on my volt meter. Is my transformer bad? Thanks

hvacfreak

some hefty voltage

...sounds like there are two transformers conflicting with each other ( control and perhaps an integral burner control with a 24 volt power supply ).

I usually run across this with Taco zone valves ( that have been wired and operating longer than I've been alive ). They have an end switch that switches a powered contact , not a dry one ( I think ) ...and yeah , the damn transformers have an inch of dust on them and have been bucking / boosting since 1955.

I have learned to to use a relay ( n.o contacts where the old stat was connected ) whenever I need to replace an old stat ( usually to combine with a cooling stat on a new ac system that I install ). And I don't have to hear anything like .." it's been working fine for 55 years " load o ' crap.

If this is your house , cut out each and every cloth covered low voltage wire and correct the 55 year old wiring mistake ...and plan on the required isolation relay ...just as was needed when the system was new. I hope I don't sound too bitter , but I've gotten caught up in the " old timers " wiring trap too many times...ok RANT TIME ...

Extra Large gold colored valves with redundant connection terminals , huge grey boxes that hang on the wall with one rusty pan head screw that are nothing more than a single pole relay , bundles of sensing bulb element held together with a twist of rusty metal wire , measuring 40 volts to energize the burner ( TT ) at 2 am after a long night at band practice ( and not knowing what I was doing on many levels , lol ), cloth covered control wire that was shorted somewhere in it's 200 ft length , any old thermostat that said WR ( I don't want to brand bash , but damnit man ) , grey boxes on the flue pipe with a sensing element caked with soot ( may or may not have the single rusty pan head screw ), clock thermostats with the plastic pins....man I don't miss residential service work ( well , maybe a little , lol ).

Belimo , RIB , JCI 350...better options for all of that crap listed above. -peace

zeke

Where did you measure the voltage- between which wires?
Don't see how you can possibly get 37V AC.

World Plumber

Double check that voltage! Where you using a digital meter? Was it 37 vols or 37 millivolts of stray voltage. You gota watch them digitals if they are senstive you'll get them millivolt readings and think you have power when you don't. If it is actually 37 volt Ac Start looking for more than one transformer and phase them. or put in isolation relays.