[BigDP]

A customer has a Honeywell RLV310A line voltage thermostat connected to one eight foot 240v baseboard heater. I've tried 2 of these in the same location and have encountered the exact same issue. The thermostat registeres the correct temperature in the room until heat is called for. Then the temperature registered by the thermostat actually goes down instead of up. And it just continues to draw heat (indefinitley I guess). As I said I've tried 2 of them and they do the same thing. Once I turn down the setting on the thermostat and it stops drawing current, the thermostat again registers the correct temperature. Any ideas as to what is going on? Hard to believe both of them were defective.
One thing to note, this thermostat is mounted directly next to a Lux low voltage thermostat that controls their radiant floor heat. The electric heat is for backup.
Thanks.

 

[Shockdoc]

A customer has a Honeywell RLV310A line voltage thermostat connected to one eight foot 240v baseboard heater. I've tried 2 of these in the same location and have encountered the exact same issue. The thermostat registeres the correct temperature in the room until heat is called for. Then the temperature registered by the thermostat actually goes down instead of up. And it just continues to draw heat (indefinitley I guess). As I said I've tried 2 of them and they do the same thing. Once I turn down the setting on the thermostat and it stops drawing current, the thermostat again registers the correct temperature. Any ideas as to what is going on? Hard to believe both of them were defective.
One thing to note, this thermostat is mounted directly next to a Lux low voltage thermostat that controls their radiant floor heat. The electric heat is for backup.
Thanks.

Is it mounted on an uninsulated wall with holes drilled in the top or bottom plate. Can it be pulling cold air from the attic or basement?
Or is the place haunted?

 

[NacBooster29]

Get an electrician to check it out. Sounds like you have a line voltage t stat set up for an exhaust fan for cooling.

 

[BigDP]

It only registers the incorrect temperature when it is drawing current. Otherwise it registers the correct temperature.

 

[svh19044]

2 wire or 4 wire? Are you wiring it correctly? Check the baseboard and look how that is wired as well...

Huh, I googled it and this is what someone said...

1.0 out of 5 stars Flawed design, December 18, 2010
By
Dave Schultz (Spirit Lake, IA) - See all my reviews


Amazon Verified Purchase(What's this?)
This review is from: Honeywell YRLV310A1026/U Digital Non-Programmable Thermostat for Electric Baseboard Heating (Tools & Home Improvement)
I believe this thermostat has a fatal design flaw --- at least for our application which is a fairly large room with significant heat loss. I installed this to replace a Honeywell Digital LineVoltPro(tm) 7000 which died after working just fine for several years. The temperature reading for this RLV310 thermostat reads from 1 to 7 degrees below the actual room temperature. (Actual room temperature measured by three different digital thermometers mounted in close proximity to the YRLV310's sensor, all measuring within 1 degree.) One would suggest just lowering the set point, but that doesn't work since the sensed temperature varies so much. Worse yet, the sensed temperature error grows larger as more power is delivered to the heaters; the largest offset occurs when the thermostat is pumping out the most power to the heater. This results in a fatal "runaway" which keeps the heater on indefinitely in our application, even when the room the room temperature get up over 75d and the set point is less than 70d.

 

[mgraw]

I agree with Shockdoc on this one. My guess would be the heater is causing cold air from inside the wall to flow through the thermostat when it is on.

I will pass on the ghost theory.

 

[BigDP]

What svh19044 has described is exactly the same issue as I am experiencing. I have tried to contact Honeywell in regard to this issue, which to me is a serious design flaw and safety hazard, with no success so far. I have 4 of these installed in my home and it makes me want to replace them all. Thanks for the input folks.

 

[macmikeman]

Slap a nest on it.

 

[guest]

What is the current draw on that 8' heater? Is it running at 240 or 120 volts?

One problem I can forsee with a true electronic thermostat is that the triac that actually switches the current WILL generate it's own heat internally, which may cause the problem the OP is having.

Come to think of it, since it is only a single heater, is it possible that the current drawn by the heater is not enough? (Kinda like how some LED dimmers have a minimum load requirement?) From the manual:

Supply: 120/240 VAC, 50/60 Hz
- Minimum load: 2 A (resistive only)
500 W @ 240 VAC
250 W @ 120 VAC
- Maximum load: 12.5 A (resistive only)
3000 W @ 240 VAC
1500 W @ 120 VAC
- Display range: 0 to 50°C (32 to 122°F)
- Setpoint range: 5 to 30°C (40 to 85°F)
- Storage: -20 to 50°C (-4 to 120°F)

So is the heater load within range?

Hold the phone, just noticed this:

The thermostat registeres the correct temperature in the room until heat is called for. Then the temperature registered by the thermostat actually goes down instead of up. And it just continues to draw heat (indefinitley I guess). As I said I've tried 2 of them and they do the same thing. Once I turn down the setting on the thermostat and it stops drawing current, the thermostat again registers the correct temperature.

Possibly the thermostat display is playing the game of showing the low temp in the room and will gradually raise to the set point?

The manual is infuriatingly short on details of what the display does.

I have baseboard heat here and may pick up one of those 'stats and see what happens.

 

[mgraw]

What svh19044 has described is exactly the same issue as I am experiencing. I have tried to contact Honeywell in regard to this issue, which to me is a serious design flaw and safety hazard, with no success so far. I have 4 of these installed in my home and it makes me want to replace them all. Thanks for the input folks.

I would try a simple test. Pull the t-stat out of the wall leaving the wires attached. Tape the opening and around the wires. Turn the heater on and see if the t-stat continues to malfunction.

 

[BigDP]

OK I tried removing it from the wall as suggested, taping the wall, and the same thing happens. As I've said before, as it draws heat, and the room starts to heat up, as verified by indpenedent thermometers, the temperature readout on the thermostat actually drops. As far as I know, an eight foot long baseboard heater at 240 volts would draw 2000 watts, so this should be ok, correct?

 

[mgraw]

OK I tried removing it from the wall as suggested, taping the wall, and the same thing happens. As I've said before, as it draws heat, and the room starts to heat up, as verified by indpenedent thermometers, the temperature readout on the thermostat actually drops. As far as I know, an eight foot long baseboard heater at 240 volts would draw 2000 watts, so this should be ok, correct?

The only thing I can think of is there is an air draft occurring when the heater is on. You said that room has a large heat loss. My guess is cold air is being drawn into the space and affecting the t-stat.

 

[Cl906um]

Some of the new thermostats I have seen like this have different dip switches to set whether you are using them for forced air, boilers with radiant heat, ... Does this one? (Keeps it from over cycling the system it is controlling.

 

[rrolleston]

Slap a nest on it.

I like those nest thermostats for electric baseboard heat. I have done a few conversions where I have installed them. And they work great.