Thermostat for gas heater!

lanchile

Hello guys! I have to replace a thermostat for a gas heater unit (Cozy) I called company but they do not have the original thermostat in stock the unit is too old. But the technician told me that I could use any 24v thermostat and I have to leave the thermiser disconnected! the old thermostat has 4 wires White-Red-Yellow-Yellow. for what I understood is:

A) in the new thermostat connect the White wire to the W
in the new thermostat connect the Red wire to the R
C) leave disconnected the two yellow wires from heater and disconnect the wires from new thermostat "thermiser" ?

Is that all right?
can anyone help me with wiring please.

rpf65

Sounds like yuo're describing either an in-floor or wall mounted furnace. Is that correct?

Just need some more information, but 2 wire heat only thermostats are still available. I just installed one about 3 weeks ago.

obieone

Can you post a pic of what you're working with?

gdb

WW Grainger might have the original thermostat, if they dont, go with a Round Honeywell, they last forever.

http://www.grainger.com/Grainger/wwg/search.shtml?op=search&N=25714&in_dim_search=1

lanchile

Thanks guys! Well it is not necessary to put the original (not longer available) someone put a Honeywell Model ETS1102-024020LP 24VAC and it worked just fine but the problem is, it has the variable resistor to adjust heat but it is very small and mounted on board. people can not adjusted easily(you need small screwdriver). the heater is an old Cozy brand (did not find model anywhere) and it is a gas unit with fan out to wall. there are four wires coming from heater. White, Red, Yellow, Yellow. White was connected to neutral, Red was connected to Hot and the yellows were connected to load in and out terminals all this in the thermostat. for What I understood was "just" connect the red and white cables to the new thermostat and leave the yellows open. and I think I am going for the Round Honeywell as it is very simple and it looks like it will last longer than those digital ones.

lanchile

rpf65 wrote: »

Sounds like yuo're describing either an in-floor or wall mounted furnace. Is that correct?

Just need some more information, but 2 wire heat only thermostats are still available. I just installed one about 3 weeks ago.

yes, it is only a gas heater! but it has four wires...

rpf65

Hope that works. There could be a problem though. The Honeywells are 24 volt thermostats. You need a transformer to power it. I believe you said the tech said that you need a millivolt thermostat. A thermistor produces a 750 mv power source to the thermostat.

On the off chance that the Honeywell doesn't work, Robertshaw sells millivolt thermostats. You would need to order model 100-502.

lanchile

rpf65 wrote: »

Hope that works. There could be a problem though. The Honeywells are 24 volt thermostats. You need a transformer to power it. I believe you said the tech said that you need a millivolt thermostat. A thermistor produces a 750 mv power source to the thermostat.

On the off chance that the Honeywell doesn't work, Robertshaw sells millivolt thermostats. You would need to order model 100-502.

it is a 24VAC thermostat.

mrbigbluelight

it has the variable resistor to adjust heat but it is very small and mounted on board.

I believe that's the heat anticipator.
It's designed to slightly heat the Tstat so that it kicks off the gas valve slightly before it kills the blower.
This keeps the blower on to draw off heat from the furnace heat exchanger after the gas valve closes. No sense in having a red-hot heat exchanger sitting there doing nothing.

The correct setting for that variable resistor is dependent upon the actual current flow through the Tstat when the units running. Measure it with an amp clamp or ammeter and set the adjustment accordingly. You should be able to see markings like "O.2", "0.4", etc.
If you don't have a meter, just adjust it about 2/3's of the way up. That'll get you in the ballpark.

lanchile

mrbigbluelight wrote: »

I believe that's the heat anticipator.
It's designed to slightly heat the Tstat so that it kicks off the gas valve slightly before it kills the blower.
This keeps the blower on to draw off heat from the furnace heat exchanger after the gas valve closes. No sense in having a red-hot heat exchanger sitting there doing nothing.

The correct setting for that variable resistor is dependent upon the actual current flow through the Tstat when the units running. Measure it with an amp clamp or ammeter and set the adjustment accordingly. You should be able to see markings like "O.2", "0.4", etc.
If you don't have a meter, just adjust it about 2/3's of the way up. That'll get you in the ballpark.

Thanks! but that is not the point here! I know I can adjust the temperature by turn it down or up (I have done before) but this thermostat is for a unit in one apt and the tenants need to adjust temperature and with this tiny thing they will not do it. I just need it to replace it with a Big unit that people can turn it up or down easily. this one is working fine, but sometimes it gets too cool and you have to adjust the thermostat a little higher and the only way it doing it with small screwdriver and the girls that live there will never open this thing to adjust temperature.

rpf65

If it is a 24 volt, 4 wire hook-up, than you should be able to use just about any thermostat. The round honeywell will work fine. When you go to the store, get the 1 heat/1cool, and it should work. SOunds like you have a really old furnace there. If the thermostat says that batteries are necessary if no "C" terminal, you will have to use the batteries. They will act as common.

lanchile

rpf65 wrote: »

If it is a 24 volt, 4 wire hook-up, than you should be able to use just about any thermostat. The round honeywell will work fine. When you go to the store, get the 1 heat/1cool, and it should work. SOunds like you have a really old furnace there. If the thermostat says that batteries are necessary if no "C" terminal, you will have to use the batteries. They will act as common.

Thanks, I will go to Homedepot today and get the round one. Thanks again!

gdb

You're getting a bunch of incorrect info about HVAC on an audio forum, I'd suggest that you google and go to the sites that are devoted to your concerns. (or hire a tech)

The heat anticipator is an electrical resistor device mounted in the center of many mechanical thermostats that fine tunes the point at which the thermostat turns off the furnace burners. It anticipates the flywheel effect of a space heating up and turns off the burners a short period of time before the space reaches the desired temperature.
The heat anticipator essentially consists of a simple thin wire mounted to a disc which is attached to the bimetallic coil. There is an adjustment arm which touches the wire and functions to vary the electrical resistance of the wire which in turn varies how hot the wire gets. This in turn warms the bimetallic coil causing it to shut down the gas burners early as determined by the heat anticipator.

gdb

The round Honeywell is availabe without the extra baseplate in a heat-only version.

lanchile

gdb wrote: »

The round Honeywell is availabe without the extra baseplate in a heat-only version.

Thank you for all the help! This morning I got the round honeywells (as you said it is just for heat) and I just connected the red and white wires and I left the yellows out. it works perfectly!!!! I try a few times and all worked fine. Next time when the tenants leave, I will re-locate the thermostat very far from heater, right now it is like five feet away from heater ( I know it is not good) But since the heater blows the warm air to the front it is not so bad. My boss called a technichian and He said just to go there and check it will be $140 and to put a new "special" thermostat will be $260. I used to work in electronics fixing amps,tv's, stereos, etc. but I never replaced a thermostat lol. I have build many diy amplifiers. But my knowledge was very low in gas heaters. I guess We never stop learning right! Here is my diy amplifier that I build not too long ago.Attachment not found.Attachment not found.

gdb

Coolness, congrats !!