Johnson and Starley Warm Air CH

bobthesod · 2 Nov 2019

Have the above fitted and is working ok, BUT think that the thermostat needs replacing as one day to get a set temp needs setting 5 and other days 6 ( no temp shown)

The wiring to the stat from the warm air unit, where the timer it situated, is two wires with a voltage in the region of 7.4v

the stat has a two wire connection..so far so good.
And we decided to upgrade to a difital display model
I purchased a Timeguard TRT033C which has three connections! i connected the two wires in all possible combinations and all that happens is that it sets the blower on.permantly it DOES NOT turn the gas jets on.
Put the old stat back and all works ok

Looking at the Honeywell DT90. if i got this would i go through the same problems, or is this a 'plug-in' replacement.
I cannot figure out why a simple on/off switch to get the gas on is giving me so much grief!

Any thoughts/suggestions welcome

Gasguru · 2 Nov 2019

Are you sure your warm air unit is not a "Modairflow" or "System ET" model...they do not use simple on/off thermostats.

bobthesod · 2 Nov 2019

Gasguru

Is there any identification that would give me a clue?

Gasguru · 2 Nov 2019

What't the model of the warm air unit...data plate is normally inside behind the front panel.

bobthesod · 2 Nov 2019

Gasguru

System E-T
model HI SPEC J32R
GC 42 451 06
Cat I 2H
Prod ID 87 AQ 119

So am i limited to certain stats, and knowing my luck not digital display?

bobthesod · 2 Nov 2019

Gasguru

I am pretty sure that the original stat worked via a mercury balance switch. What is the tech reason that a normal on/off switch wont be suitable. My small knowledge of electricty looks at a two wire set up as just a simple switch, could understand it a bit if there were several wirew ( 1 to turn on system 1 for gas, 1 common) but just two i cannot get my head around esp as it is old style technology

Gasguru · 2 Nov 2019

Originally (back in the 60s) when warm air was first installed the old Honeywell mercury bulb stat was common.
The replacement warm air unit has System E-T (even temp) and the stat normally says ET on it with a numbered dial.
AFAIR it has a thermistor inside and does not switch as the original on/off stats did but rather indicates the room temperature back to the warm air unit control board.

bobthesod · 3 Nov 2019

It would be nice to know what the temp is..a number means nothing lol

Bob100000 · 31 Dec 2020

Sorry for joining this thread so late, but I thought I'd better answer for the reasons below:

The J&S System-ET heaters use a special type of thermostat called a "Thermistastat". You CANNOT replace this by any other type of thermostat, and certainly not a simple make-or-break on/off device. It can only be replaced by a similar Thermistastat. A Thermistastat can be recognised because it has numbers instead of actual temperatures.

WARNING: It is is very very easy to cause serious damage if you use the wrong thermostat on a J&S System-ET. Shorting out the two wires to the thermistastat can damage the control board and there is a specific warning about never trying this in the installation instructions. This means the old trick of removing the thermostat and manually shorting the wires must NEVER be used.

If you have a J&S System-ET heater then do not even think about changing the Thermistastat for some other device!

muggles · 31 Dec 2020

Bob100000 said:
Sorry for joining this thread so late, but I thought I'd better answer for the reasons below:

The J&S System-ET heaters use a special type of thermostat called a "Thermistastat". You CANNOT replace this by any other type of thermostat, and certainly not a simple make-or-break on/off device. It can only be replaced by a similar Thermistastat. A Thermistastat can be recognised because it has numbers instead of actual temperatures.

WARNING: It is is very very easy to cause serious damage if you use the wrong thermostat on a J&S System-ET. Shorting out the two wires to the thermistastat can damage the control board and there is a specific warning about never trying this in the installation instructions. This means the old trick of removing the thermostat and manually shorting the wires must NEVER be used.

If you have a J&S System-ET heater then do not even think about changing the Thermistastat for some other device!

You seen to have rather a habit of resurrecting old threads on J&S warm air units

diynot

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Johnson and Starley Warm Air CH

Similar threads