Block Heater Thermostatically Controlled

[JLR]

I am thinking of taking on the obligatory chore of adding both external thermostats for my block heaters as well as three way switches that would allow me to place the block heaters in thermostat mode, manually on mode and off mode. While I have done this on several boats in the past, for the first time, I find myself with a Hatteras OEM setup on my 1292 DDEC's which provides a separate light switch looking box in the engine room for each block heater to manually turn them on and off with an indicator light that shuts off when the block heater reaches temperature. Here is my question. With all of the wiring in one location, it should be really easy to simply add two new thermostats and two three way switches to accomplish what I want. I am surprised that there appears to be no pre-made three way switches, at least I have seen, that go from thermostat mode, to manually on mode, to off mode. Does anyone know of such a setup. The wiring will be easy. I am just looking for a way to minimize the number of pieces involved. Alternatively, I'll ask the same question I asked years ago--is there a way to turn on/off the block heaters through the internet with an appropriate relay of some kind? I always have an internet connection at the boat. I do not think the Smarthome remote controlled thermostats are robust enough for the block heaters.

 

[JLR]

Alternatively, I'll take an internet controlled on/off switch capable of handling the voltage/amperage of the block heaters. I want to make sure that I never get to the boat without having been able to turn on the block heaters remotely or thermostatically for several hours before leaving the dock.

 

[Boatnut]

I am thinking of taking on the obligatory chore of adding both external thermostats for my block heaters as well as three way switches that would allow me to place the block heaters in thermostat mode, manually on mode and off mode. While I have done this on several boats in the past, for the first time, I find myself with a Hatteras OEM setup on my 1292 DDEC's which provides a separate light switch looking box in the engine room for each block heater to manually turn them on and off with an indicator light that shuts off when the block heater reaches temperature. Here is my question. With all of the wiring in one location, it should be really easy to simply add two new thermostats and two three way switches to accomplish what I want. I am surprised that there appears to be no pre-made three way switches, at least I have seen, that go from thermostat mode, to manually on mode, to off mode. Does anyone know of such a setup. The wiring will be easy. I am just looking for a way to minimize the number of pieces involved. Alternatively, I'll ask the same question I asked years ago--is there a way to turn on/off the block heaters through the internet with an appropriate relay of some kind? I always have an internet connection at the boat. I do not think the Smarthome remote controlled thermostats are robust enough for the block heaters.

Seems like you could use a relay connected to the thermostat using the contacts to switch the load of the heaters, just like the heat strips on a heat pump.

 

[bostonhatteras]

That's simple. just take your thermostat and wire a switch (1000 watt capable, or whatever the block heaters call for) next to it. Only one of the devices will be transmitting power at any one time. even if you had the thermostat turned up and the manual switch on its still the same power going to the heater. So more technically, splice a wire into the hot before the thermostat and terminate it at the new switch. splice into the hot wire after the thermostat and terminate that at the new switch. This way you have your manual switch and your thermostat. Parallel wiring.

 

[bostonhatteras]

Conversely you could try one of these. The model pictured here is an AUBE technologies TH115 A/F/AF Programmable thermostat. We have used them for electric radiant heat in bathroom floors. just happened to have one hanging around. This one has 12 ga wire so its probably able to do 1500 watts. Ive never looked at the manufacturers web site

 

[JLR]

All very helpful. I now see how best to wire the thrmostat and switch. And, because power will often be interrupted for a moment when I turn off shore power and switch over to my gensets, I will not be able to use a programmable thermostat. So, if I can combine the relay concept for remote control with the thermostat and switch, I would be all set. Boatnut--although I am generally familiar with relays, could you suggest in more detail how one would work in my application looking for internet controllable on/off? Thanks.

 

[davidwigler]

Plug it in here. These work great!

http://www.amazon.com/Lux-Heating-C...qid=1397213996&sr=8-4&keywords=Thermostat+100

 

[JLR]

Finally honing in here. I have found the wall mounted mechanical thermostats to use. I now need to replace the wall mounted (looks like a regular surface mount home light switch toggle in a box) from a single on /off toggle to an on/off/on toggle switch that will mount in same wall mount switch box. I know I could use smaller on/off/on toggles and make a box but I prefer to simply pull out the existing toggle and replace it with an on/off/on toggle which is non momentary, preferably in brown. The only ones I can seem to find from Leviton etc are momentary ons. No good. I need the toggle to go one way on for thermostat mode, center off and the other way for manual mode. I assume these are common but can't seem to find one. Need to handle 20 amps. Any ideas? Thanks.

 

[bostonhatteras]

http://www.globalindustrial.com/p/e...Wall-Switches-pricegr&infoParam.campaignId=WU

You may have been searching incorrect terms. what you are looking for is double pole double throw switch. they are not common as household style toggle switches. A three way switch as you stated before is for a circuit that can be turned on and off from two different locations, such as a long hallway. a fourway switch allows switching from three different points.

BTW the programmable thermostat I recommended before has a power failure feature that retains settings for up to 6 hours. That would allow changing from shore to genset power or even a short cruise.


http://www.diycontrols.com/p-7405-honeywell-econnect-wireless-line-voltage-thermostat-w-gateway.aspx
I just did a quick search for 'remote control line voltage thermostat' and got plenty of leads.

 

[Boatnut]

I am thinking of taking on the obligatory chore of adding both external thermostats for my block heaters as well as three way switches that would allow me to place the block heaters in thermostat mode, manually on mode and off mode. While I have done this on several boats in the past, for the first time, I find myself with a Hatteras OEM setup on my 1292 DDEC's which provides a separate light switch looking box in the engine room for each block heater to manually turn them on and off with an indicator light that shuts off when the block heater reaches temperature. Here is my question. With all of the wiring in one location, it should be really easy to simply add two new thermostats and two three way switches to accomplish what I want. I am surprised that there appears to be no pre-made three way switches, at least I have seen, that go from thermostat mode, to manually on mode, to off mode. Does anyone know of such a setup. The wiring will be easy. I am just looking for a way to minimize the number of pieces involved. Alternatively, I'll ask the same question I asked years ago--is there a way to turn on/off the block heaters through the internet with an appropriate relay of some kind? I always have an internet connection at the boat. I do not think the Smarthome remote controlled thermostats are robust enough for the block heaters.

The answer to your question about using the internet is there is a simple way to do it. A small relay with contacts rated for the heaters will do the job. The problem of course is the contacts in the thermostat will not carry the current required for the heaters, but they are heavy enough to energize the relay coil. Set up this way the relay carries the higher current. If you look at some home heat pump systems, this is the same way they control the heat strip in those units. By using the relay a couple of 3 way switches added to this setup would accomplish everything you want to do. If you are thinking of a more attractive switch for a remote, any quality switch will work, for the switch in the bilge you could use a double throw single pole center off toggle switch. You should be able to leave the pilot lamp where it is. I like the idea of being able to turn the unit on or off via the internet.

 

[JLR]

Now that I have the thermostats, my mechanic is having trouble with wiring. Each block heater is 220v and is controlled by a simple household looking toggle switch. Each block heater also has a 220v indicator light which turns on when the heaters are working and off when the internal block heater thermostat turns off the block heater. Each block heater has three wires coming from it to the toggle box. The new external thermostats are intended to be put in the circuit before the toggle switches so that the toggle switches can be left on all of the time but only work when the external thermostats pass current to them. By the way, the external thermostats can be wired for 220v use and have three wires coming from them. Here is the question. Why can't the mechanic simply break both leads (220v) from the hot sides on each toggle switch, insert the external thermostat there and then return from each external thermostat 220v back to the hot side of the toggle switch? My terminology may be off but the concept should be simple. In other words, simply place the external thermostats in line before the toggle receives any hot 220v source?

 

[bostonhatteras]

Now that I have the thermostats, my mechanic is having trouble with wiring. Each block heater is 220v and is controlled by a simple household looking toggle switch. Each block heater also has a 220v indicator light which turns on when the heaters are working and off when the internal block heater thermostat turns off the block heater. Each block heater has three wires coming from it to the toggle box. The new external thermostats are intended to be put in the circuit before the toggle switches so that the toggle switches can be left on all of the time but only work when the external thermostats pass current to them. By the way, the external thermostats can be wired for 220v use and have three wires coming from them. Here is the question. Why can't the mechanic simply break both leads (220v) from the hot sides on each toggle switch, insert the external thermostat there and then return from each external thermostat 220v back to the hot side of the toggle switch? My terminology may be off but the concept should be simple. In other words, simply place the external thermostats in line before the toggle receives any hot 220v source?

why would you want the thermostat to be in line before the toggle switch? both the thermostat and the toggle are in fact switches. one is just more complicated than the other. if they are truly wired in series then either one being off will open the circuit of the heaters. Its seems more intuitiive to have the toggle first, then thermostat, then heater. The intuitive part of this for me is this; a layman knows when a toggle switch looks like its off and knows when it looks like its on. If the toggle is in line first then just by casual observation most will assume there is no juice flowing to the thermostat and downstream , the heater. if the thermostat comes first there can be numerous unintended consequences. the thermostat may be open or closed and there is no way to know except to test for voltage. Someone may see the toggle off in this arrangement and assume there is no voltage but when they play with the wires to the thermostat they will find out there may actually be voltage because the person closes the circuit the toggle was opening. the person will complete the cicuit and get electrocuted. It seems akin to putting a circuit breaker AFTER a load. btw, doesnt the thermostat have a manual off? that would make the toggle switch completely redundant

 

[JLR]

Thanks for the good suggestion. It makes sense. The thermostat does not really have a manual off. However, if I turn the dial down to 40 degrees, it will essentially stay off unless the ambient temperature drops that low. The only reason I wanted the thermostat before the toggle is so that the indicator lights would not be on all the time when the toggle is on. However, your explanation makes sense and those lights should go out, even if the toggles are on so long as the block heaters have heated the block to the proper temperature.

 

[Boatnut]

There is only one reason that I can think of that would require the switch to be on the load side of the thermostat. It is possible the temperature sensor is electronic and requires power to operate. If it is a mechanical thermostat then it wouldn't matter. If you don't know which type it is, maybe check with the manufacturer, although checking with the manufacturer could be a problem if it's a low priced Chinese unit.

Good luck

 

[JLR]

Thanks so much for the help. The thermostat is made by Chromalox (see link below) and appears to be a fairly robust unit. I used two of them before in my 56 and will be using two in my 74.

http://www.chromalox.com/catalog/resources/MOD-WCRT.pdf

 

[Genesis]

"Positive snap-action switch" = Mechanical, requires no power to operate.

 

[JLR]

Thanks Karl. Nice to know. Also, in reading the literature, it appears as if placing it in the "Lo" setting is akin to a manual off mode.

 

[Boatnut]

The way the specification are written, it appears a contactor is needed to run the heat and cool, in this case of course it is heat. Not knowing what the current draw of heaters is, it's hard to determine if the thermostat will handle the load without using a contactor. You also mentioned turning this on or off via internet, using the contactor could be used for both purposes.

 

[JLR]

By contactor, do you mean a relay?

 

[bostonhatteras]

''The WCRT Room Thermostat is designed to
directly control an individual heater. Using an
external contactor, it can control several heaters''

Contact sets are used when a smaller switch cannot handle the amperage, or it is not logical to run high amp cable to the point of user location. A good example is the starter switch on your helm. that start button is a low amp switch which then sends a smaller amount of amperage to a large switch on the starter motor, the solenoid. The solenoid then switches the high amperage. This eliminates having the huge battery cables coming to the helm. only small cable is necessary. The battery bank parallel switch is another and possibly better example.

This quote I cut and pasted from the thermostats info page would tell me that a contactor, or relay, is needed if you want to EXCEED the amperage capability of the thermostat. My reading of the instructions tells me that the thermostat alone will work fine if using one heating device. 25 amp for 110-220 is a robust thermostat. 25 amps at 220 is a good amount of electricity it is passing.