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Wiring a boiler. honeywell L8124A, C and aYr845a t stat calls for heat the circulators run but the boiler doesn'T FIRE what am i missing

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SOURCE: I have a coleman evcon

The most common wiring is: This sometimes varies as to installers preferance.
Red wire is your supply power to the T-stat. R terminal
Green wire is the blower fan. G terminal
Yellow wire is compressor contactor Y terminal
older units used a blue wire to Y
White wire is heat auxilary or black wire W terminal
Orange wire is reversing valve O terminal
Blue wire is the common C terminal
Black wire can be emergency heat E terminal
Best thing to do is replace wire for wire from t-stat to t-stat
or write down the colors to which terminal on the old t-stat and match to the new. make sure you SECURE POWER to the Air Handler, furnace and condenser before replacing any t-stat.
It is very easy to short the wires out if the power is left on and take out your A/H low voltage fuse or transformer.

Posted on May 18, 2008

  • 1 Answer

SOURCE: keston c40 honeywel 9400c programmer

do a s plan plus and buy a poly plumb roomstat combined programer with built in relays as you require the relays to stop back feed! simple!

Posted on Jul 23, 2008

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SOURCE: No hot water honeywell st6400c

HW valve was stuck in the open posiion and the micro-switch was not working so thats why boiler and pump were not starting. Bled system to below the level of the valve to be changed, and replaced valve with a drayton ( easy quick change of valve head if needed no screws )

Posted on Sep 17, 2008

  • 659 Answers

SOURCE: hot water boiler will not ignite

Check all your limit switches on this unit. One of them is either tripped or bad.

Posted on Apr 07, 2009

  • 234 Answers

SOURCE: what would the correct high and lo and diff

I would say high if you need cooling. If the tempature is cool enough for you then set it to low.If you are hot and need more cooling then high.

Posted on Apr 07, 2009

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1 Answer

Boiler runs but not getting any heat coming out of the radiator


When you have a call for heat from the t-stat, the first thing that happens at your boiler is the circulator turning on. Turn off the stat, let the boiler cool down, and stand by the boiler when someone else turns the stat on. Put your hand on the circulator. If you feel it start to run when the stat is turned on, it's OK.

If it's not the circulator,then it sounds like the system is airbound and must be purged.

If you have actual radiators instead of baseboard, then each radiator must be bled. You can get a radiator key from any good hardware store. It may take a few circuits around the house to chase the air down so bleed each radiator at least twice.

Mar 19, 2017 | Heating & Cooling

1 Answer

I have a hot water boiler with 3 zone valves and 2 circulation pumps. I see no relays wired to pumps. Pumps run constantly


Sounds like a lot of unknowns from your article. Here are some basic checks

- if they are the honeywell zone valves and you try to open them and get resistance than 9/10 times the t-stat is not calling for heat and the valve should be closed
-if stat is calling and wants heat zone valve lever should be free of resistance when moving it
- 15-20 psi is a little high but could be normal based on the size of your place and the temperature you are reading these pressures at
-with the pumps always running seems to me that the pumps are hard wired to a constant electrical source, if you want optimal control install a taco zone controller

May 21, 2017 | Water Heaters

1 Answer

Hi, I have a baxi solo boiler WM60/4RS and a Landis & Gyr RWB252 timer but my Honeywell T6160 thermostat has nether been connected, can anybody shed light on the wiring connections please.


The color code for thermostat wiring is as follows.
The "R" terminal is power into the stat from the boiler control transformer. Normally 24 volts. The "Y" terminal is for cooling. Normally left blank for a boiler. The "W" terminal is for heat. This one used to start the heating cycle.The "G" terminal is for fan operation. Probably not used for a boiler. Check the boiler terminal board for these functions and write down the wire color on each one. Match the boiler colors to the right function on the stat. If you need more than this, let me know.

Jan 06, 2014 | Honeywell Programmable Thermostat Heater

1 Answer

My Honeywell ST 6400C won't heat the hot water the light comes on but pump doesn't run or boiler fire. But does work on C/Heating.I can get hot water only by running the C/H and manually opening the hot...


it sounds like the motor in the motorised valve is not working on some models you can just change the head /motor , check cylinderstat (hot water stat) is working

Dec 14, 2010 | Honeywell Heating & Cooling

1 Answer

IVE GOT A HONEYWELL T87A 3 WIRE THERMOSTAT MOUNTED ON THE WALL AND WHEN I WANT TO TURN ON MY HOT WATER BOILER I HAVE TO LOWER THE T-STAT SETTING INSTEAD OF INCREASING IT TO GET THE HEATING SYSTEM TO TURN...


I would switch to a two wire heating only stat It sounds to me like they have the boiler wired into cooling side. Do you also have to set switch on your t-stat to cooling or leave it on heating. Just curious. I would still go with two wire stat. Thanks.

Nov 11, 2010 | Honeywell CT87B ROUND HEATING&COOLING...

1 Answer

Temperature fluctuates


Actually that thermostat is adjustable for only +/- 1 degree. I would make sure it is located close to a radiator/register, whichever you have, to help close that 8 degree variance. The thing about hot water heat is that even when the boiler shuts down those radiators are still putting off heat, so the temp can still shoot up a few more degrees after the stat has been satisfied. Is the boiler shutting down when the stat hits 71* ? If not then the stat may be bad. Honeywell carries a 5 year replacement warranty on that stat. I use the Honeywell Focus stats in almost all my installations. They are a very dependable thermostat. Feel free to ask anything else that will help solve your problem...Rob

Dec 16, 2009 | Honeywell Focus 6300B 5-2 Days...

1 Answer

Cannot get central heating working,for honeywell ST6400 programme


with y plan 3 connections on programmer HW on HW off CH on HW on to cylinder stat then HW call to Orange on Mvalve to power boiler and pump HW off to grey wire on Mvalve to close hot water CH to room stat common then heating call to white on Mvalve

Jun 13, 2009 | Honeywell Programmable Thermostat Heater

1 Answer

Honeywell RTH230B will not call for heat.


On a call for heat an internal switch should connect Rh and W, if it does not the stat is bad. Try it with no wires connected.

May 18, 2009 | Honeywell Focus 6300B 5-2 Days...

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