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Author Topic: Thermostat  (Read 2544 times)
opus
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« on: September 03, 2011, 12:22:03 PM »

I am looking for a couple simple thermostats to turn my heater fans and Webasto on.  I will need probably 3 of them.

Example: Being parked over night, I want the Webasto to turn on at X degrees inside the bus.  Then I want a few fans to turn on at Y degrees.  Then of course they would go off when they hit Z degrees.

Simple suggestions please.  Smiley
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bevans6
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« Reply #1 on: September 03, 2011, 12:33:39 PM »

Temperature range and what is the control mechanism they need to turn on and off?  the easiest is a simple mercury switch Honeywell type, it makes and breaks a low current control mechanism.  The thing about the mercury switch type is if you install it level, it works in synch with the thermometer it also has, but if you mount it at an angle, you can actually control to quite low temps - I use one in my workshop that is set to come on at 33 degrees as a minimum, while normally the minimum is around 45 - 50 degrees.  The other kind that is cheap is the bi-metal spring type.  It is what is usually used in RV's because it is NOT sensitive at all to level or to bouncing around, which the mercury type definitely are.  There are now very inexpensive digital thermostats as well, I have never played with one to see what the temp range actually is - I think I will do so and figure that out.

If your devices need more than a simple on/off then maybe you could drive a relay of some sort with the thermostat.  I wouldn't ask them to switch more than a minimum of current, the spec is probably available on-line.  The relay would depend on what you need to control.  The Webasto is probably designed to be controlled with a thermostat, the fans probably need the relay.

Brian

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opus
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« Reply #2 on: September 03, 2011, 12:38:48 PM »

Temperature range and what is the control mechanism they need to turn on and off?  The Webasto is probably designed to be controlled with a thermostat, the fans probably need the relay.

I would think the temp range would be between 60-70.

The Webasto would be a simple on off.  I guess you might be right on the fans.  I was going to break the wire at the fan motor itself and put the thermostat on the wall.  I guess the best bet would be to go with something that could handle motion.  I couldnt seem to find anything less than $30.  Then again, wasnt sure what I was looking at.

What relay would I want to use?
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luvrbus
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« Reply #3 on: September 03, 2011, 12:43:06 PM »

I am sure somebody here will tell you how to do it but I thinking that has to be done with the Aqua Stats something has to read the temperature difference ?
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« Reply #4 on: September 03, 2011, 12:44:52 PM »

I was just thinking that at a certain air temp, it would close and then at a certain air temp, it would open.  Didnt think it would have to be more difficult than that.  Kinda like my thermostat on the wall in the house that does the same thing....I think.  Smiley
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« Reply #5 on: September 03, 2011, 12:53:19 PM »

I just know the Aqua Stats are used on most of the heating systems like the Aqua Hot,Hurricane,Primus and others
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« Reply #6 on: September 03, 2011, 01:08:08 PM »

I am thinking those tap into water, right?  I wouldnt want to do that.  I would however not be opposed to attaching a "bulb" to the pipe or hose, which would relate the water temp - the difference in the pipe temp.
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bevans6
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« Reply #7 on: September 03, 2011, 01:16:33 PM »

An aqua stat is basically a thermostat that controls the temperature in a hot water boiler type system, which is about what a Webasto is.  It turns the boiler on and off to keep the water temp at a certain temp.  So you would want that to control the Webasto, and it probably comes with one anyway.  You have to control it somehow.  After you have the  water hot, you have to control how it heats your bus.  I can think of two ways to do that, one is valves to open and close a path to a radiator, if it calls for heat you open a valve, heat flows, bus gets warm.  You can add to that fan control, if you call for heat then the fan also turns on and you circulate the warm air.  I bet the webasto guys have that figured out too.  As far as what relay, that depends on the voltage and current draw of your fans I would think.

Too complicated for me!  I have the old propane furnace when it gets cold!

Brian
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« Reply #8 on: September 03, 2011, 01:28:23 PM »

This is what I used to control the fans on my Primus unit and that was White/Rodgers snap disc they come in a bunch of different temperature setting fixed or adjustable cost about 10 buck each they are pretty simple they just read the temperature and turn the fan off and on mine were 90*to 110* so I used a wall mounted thermostat in conjunction   

good luck
« Last Edit: September 03, 2011, 01:34:53 PM by luvrbus » Logged

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« Reply #9 on: September 03, 2011, 04:31:16 PM »

When the Webasto is on, the circulator pump is going to pump it through the whole bus.  I am not changing that.  It will continue to go through about 5 heaters, each with fans.  I need the fans to come on when the temp calls for it, as well.

I am guessing I would have the Webasto turn on at say 62 and the fans on at 62 as well probably.  Just working this out in my head, now that we are using heat again. 
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Sean
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« Reply #10 on: September 04, 2011, 07:41:40 AM »

Getting the Webasto to work right is definitely not a simple matter of a single thermostatic switch, so think this through carefully.

Also, never, ever put a switch (thermostatic or otherwise) in the main power feed to the Webasto.  Always use the signal input to the control box to turn the unit off and on.  Otherwise, you could interrupt power while the unit is performing its cool-down cycle, and that will fry the whole Webasto in short order, and quite possibly start a fire.

The Webasto has a built-in thermostat, which will turn the burner on and off based on the coolant temperature, so you don't need to provide that function.  And the Webasto itself provides a signal to turn the circulating pump on and off.

Where you will need an aquastat is in the coolant line to the fan heaters.  When your residential thermostat is calling for heat, you don't want the fans to come on unless and until the coolant is actually up to working temperature.  In our system, from a cold start, it takes about 10-15 minutes from when we first turn it on until the fans come on.

You will also need an aquastat on your domestic hot water heater, if it is the type with a hydronic heat exchanger (highly recommended if you have a Webasto anyway).

Typically, the residential thermostat(s) are connected to a system of relays which engage the Webasto system (through the on/off control signal) and the circulating pumps and heater fans.

If you don't want to engineer such a system yourself, Sure Marine sells a control box with all the necessary relays already wired up, and a terminal strip where you connect the Webasto and your thermostats and aquastats.

HTH,

-Sean
http://OurOdyssey.BlogSpot.com
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opus
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« Reply #11 on: September 04, 2011, 11:48:18 AM »

I agree, the signal wire for the Webasto, I know that much.  I dont have domestic hot water.  I have an additional circulator pump as well.  I can tie the two together I would assume.  Actually, there is a spot to hook an additional pump to the Webasto.
I wont however be breaking any coolant lines so I will have to figure out a way to turn the fans on without the aquastat.  Whether it be a temp probe connected to one of the coolant lines or such.

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