Strange Activity with the Hurricane System

[Dick Simonis]

This has been an interesting couple of months between Voltage spike, gen set deciding not to start, and now the Hurricane seems to have developed dementia.

With the temps around here forecast to be in the teens and 20's, I did my normal thing of disconnecting the water maker line and setting the thermostats to 45 figuring this would keep the coach from freezing.  This morning I stuck my head out and it was 19F and the hurricane was running...OK, all is well.  Later on it was still running and when I went inside it was 52, well above my set point but yet the front zone was running.  Turning off the thermostat did not shut off the zone yet the thermostat was not commanding heat. OK, faulty thermostat?   I shut off the master switch and it shut down OK and I figured I would check it out later in the after a meeting.

Now it's working perfectly on both zones so I'm a bit baffled!!!  Tough to fix something when it ain't broke.

I'm wondering if the zone that is in the water bay is somehow turning on the living area zone since it's the only one I didn't check.

Has anyone seen anything like this?   It's going to be real nippy for the next week.....well below freezing so I kinda need to make sure it will be OK.  Heats OK, just acting odd.

[Edward Buker]

Dick,

I'm not a Hurricane owner, my coach has an Aquahot. I'm not sure what your unit uses to turn on the zone pump but in my case it uses pluggable relays. The thermostat is a low current device which triggers the relay and the relay controls the pump. If your unit uses relays it could be that one of them hung up or it could be that the logic circuit that was used in the thermostat or a circuit board to control things was in a stuck fault and not latching as it should. If you get the condition again and you can find relays, tap on each one and see if the circulator stops. If so change that one relay. The springs that unlatch the relay age and in my case they are within the housing of the Aquahot so they see a lot of temperature cycles and heat that would help age the springs. If no relays are part of the circuit and dropping power always fixes the problem, then you most likely have a thermostat or some control board circuit that is faulty. This is just some thoughts on possibilities, the Hurricane owners would have better advice.

Later Ed

[Joel Weiss]

Dick:

As someone who has a Hurricane and is reasonably familiar with its behavior, I have to admit that I am a bit perplexed by what you report.  It has been my understanding that the front and rear zone fans are simply wired through their respective thermostats and I've never observed a fan being on without the corresponding thermostat being on also.  I didn't think the basement thermostat was in any way interconnected with the zones upstairs.

I'll continue to think about the problem and will post anything that might occur to me later.

Joel

[Dick Simonis]

I know....it's been really strange.  This morning it's 18F outside but inside the coach it's a balmy 54 in front and 48 in the rear with the thermostats set at 45.  The Hurricane isn't running at the moment but the temps indicate it has been.

Ed's comments about a possibly stuck relay would be valid except that option is only on the fans not on the control circuit.  Somehow the thermostat inputs to the control board appear as if they are being overridden by another signal.  Aside from this anomaly it appears to be working perfectly

Both thermostats were replaced last year with digital and have proven to precisely control the temps within one degree of the set point.  I can hear the relays actuate and they are doing so at the correct temp so I'm fairly confident they are functioning OK.

Today it's warming up to 40 or so and I'll have time to dig into this a bit further.  I'm thinking that by operating each zone I can tell which ones are commanded on by observing both function and the control panel indicator lights,  The water bay zone will be a bit trickier as I'll have to manually bypass the aquastat.

Tomorrow the coach goes into a shop for the genny and cabinets and I need to have a way to keep the temp up as it's going to continue being in the teens and 20's for the forseeable future.

[Joel Weiss]

We still have the original analog thermostats; what digital brand/model did you use as a replacement?  The analog works fine, but the temperature control might be better with a digital model.

[Dick Simonis]

Joel, I went with a White Rodgers heat pump thermostat that really works nice as it automatically shifts the AC fan from low to high and back again as neccesary.

http://www.ebay.com/itm/Thermostat-White-Rodgers-Heat-Pump-3-stage-1F83-277-/260229107980#vi-content

Snce it's a 24V unit, I'm just running on the internal battery and so far have not had to replace them but will before we head our for the summer.  I have heard that it will work on 12 VDC just fine but havn't had an need to try it that way.

Dick

[Joel Weiss]

Thanks, I just discovered that Dometic has a simple digital version of the thermostat, with automatic fan speed switching, for ~$30 at many RV parts places (here's one: [url]/http://www.americanrvcompany.com/Dometic-3313192000-Polar-White-Single-Zone-LCD-Thermostat-Camper-Trailer-RV_p_13954.html[url].  

[Gerald Farris]

Dick,
I can not see any way that the basement heat exchanger is causing the problem that you described. It sounds like a thermostat problem. The thermostat has to do two things to enable the Hurricane to heat the coach. First it has to supply current to enable the heat exchanger fans to run. Second it has to tell the Hurricane control board to turn on the circulation pump The same pump is used for all three zones, therefore the only difference between zones is which heat exchanger fan is activated. If only one zone is heating, all heat exchangers are hot, but the fans only run were heat is needed. Since apparently both commands were being delivered at the same time, the likely defective part is the thermostat.  

Gerald

[Edward Buker]

Dick,

The original analog thermostat uses a set of robust mechanical contacts and you are supplying all the fan current with just the thermostat switching without a relay from what I saw of the Hurricane literature. Over time could be a problem with a digital thermostat if it was not rated to handle the required current. You may want to check what the thermostat switching current rating is vs the demand of the fans and the pump input for the Hurricane control board. You could add a relay if needed to handle the current.

You also mentioned running the thermostat just off of a thermostat battery that you had not changed. Circuits get flaky when the voltage supply is low, I would change that battery just to rule it out. Like Gerald, I also think the thermostat is at fault and you should be able to measure the voltage on the (W) white wired terminal with the heat on and off and see what the values are when the unit is working properly. Then check it when it acts up and see if the thermostat connection for the W wire is connecting and disconnecting properly with temperature change. I believe that the white wire and terminal is the furnace control but that needs to be confirmed with measurements. If the voltage does not always toggle properly at the thermostat terminal then it is at fault.

Later Ed

[Dick Simonis]

I was under the impression that the thermostat only provides a on/off signal via the relay(s) and is not a source of voltage and no system current goes through the contact.....especially since the wiring is only about an 18 gage.  Fan current is supplied from the Hurricane brain box directly to the fans.

Also, Joel I did look into that thermostat and, if I remember correctly, it can not be retro-fitted to older units.  Something about the signal cable and controller are different.  Something needed to be installed in the AC unit and new cables run.

Good point on the batteries though and I will change them the next time I see the coach.  Once again it's in the shop..this time to repair the cabinet smoke damage and fix the gen set.