Possible humidistat problem

[sibleyj]

Hi,

We have a home in South West Florida which is unoccupied most of the time. When we are away from the house we use the following settings.

Humidistat - 65%
Thermostat - 75 degrees and 'COOL'
Fan - AUTO

As far as I can guess the above settings will mean that the air conditioning will be controlled by the humidistat and will only switch on when the humidity reaches 65%. Even if the temperature goes above 75 degrees the air will not switch on as the humidity is the controlling factor.

The reason I'm asking is that we have been using these settings since we purchased the house in November. In November the electricity bill was $13 (cooler less humid weather + no-on in house). The bill has steadily risen as expected given rising temperature and humidity to the point in June where the bill was $28 (house unoccupied), however the bill for July was $85 (house still unoccupied). Our homewatch lady says that the settings are as above and that the temperature in the house is 'comfortable'. This has rang alarm bells with me because as I see it the temperature in the house should be quite high as the humidistat should be controlling the air conditioning not the thermostat. It looks like the thermostat is keeping the temp down to 75 and the humidistat is not working.

Can someone please tell me if I'm making sense? Thanks

[HayZee518]

unless you have a seperate enthalpy control controlling the a/c system then the a/c system will be working off the unit's thermostat. the "desired" humidity is just an indicator. the proportional band for air conditioning doesn't use a "heat/cool anticipator" like for oil or gas heating. the heat anticipator "anticipates" the approach of a set point so the heater doesn't short cycle. not the same in an a/c system. 72 degrees is a comfort zone setting for a/c.

[sibleyj]

unless you have a seperate enthalpy control controlling the a/c system then the a/c system will be working off the unit's thermostat. the "desired" humidity is just an indicator. the proportional band for air conditioning doesn't use a "heat/cool anticipator" like for oil or gas heating. the heat anticipator "anticipates" the approach of a set point so the heater doesn't short cycle. not the same in an a/c system. 72 degrees is a comfort zone setting for a/c.

Hi, Thanks for responding.

I'm a little confused. I thought that I essentially had 2 controllers. A thermostat, for when we were home and wanted to control the air for a comfortable temperature. And a humidistat for when we were away so that the air only came on to control humidity, thus preventing mould growth and no need for a comfortable temperature (and saving on electricity bills).

When we have been back to the house after being away for a while the temperature has been very hot, until we've turned off the humidistat and allowed the thermostat to take control (of temperature, and a matter of course humidity). This indicates to me that the humidistat is the primary controller when it is set, whilst the thermostat doesn't figure.

[HayZee518]

the thermostat has a liquid filled bulb and capillary that expands and contracts as temperature increases and decreases. this acts upon a set of electrical contacts which control your condenser, compressor and air handling fan. An enthalpy control is basically a spring loaded piece of plastic strung between two points that lengthens or shortens depending upon how much moisture [or humidity] is in the air. this is also connected into the a/c control circuitry [if the system has a true humidistat] otherwise you'll have to rely on the thermostat for settings.

[sibleyj]

the thermostat has a liquid filled bulb and capillary that expands and contracts as temperature increases and decreases. this acts upon a set of electrical contacts which control your condenser, compressor and air handling fan. An enthalpy control is basically a spring loaded piece of plastic strung between two points that lengthens or shortens depending upon how much moisture [or humidity] is in the air. this is also connected into the a/c control circuitry [if the system has a true humidistat] otherwise you'll have to rely on the thermostat for settings.

Hi,

Sorry, but 'Chat' doesn't seem to be working.

I'm pretty sure that the system has a true humidistat. As I said when the humidistat is on it appears to be bypassing the thermostat as even though the t/stat is set to the 75 degrees, the temperature in the house is way higher than that when the humidistat is engaged.

My concern now is because the electricity bill has gone up over 3 fold since june, and our homewatch lady says that the temperature in the house is fine. This indicates to me that the humidistat is not acting as the primary controller any longer.

[HayZee518]

if you could get me a schematic diagram of the unit - I could tell right away if there is a humidistat in the circuit.

[LazyPup]

In residential thermostats “Temperature” is always the primary function. When you have a thermostat that has a “humidity control” the humidity control is “in addition to temperature” but never “in lieu of temperature”.

[sibleyj]

In residential thermostats “Temperature” is always the primary function. When you have a thermostat that has a “humidity control” the humidity control is “in addition to temperature” but never “in lieu of temperature”.

Thanks for your responses, all.

HayZee518, I'm afraid I don't have a schematic at the moment.

I'm still a little confused. Here are the questions that are going through my head at the moment.

i) the humidistat is a seperate unit to the thermostat. Would this make a difference to how the controllers worked together?
ii) If the humidistat worked in addition to the thermostat, what is the point of the humidistat? The thermostat would keep down both the temperature and the humidity based on what ever it was set at, just like when you're at home and the humidistat is switched off (as per the instructions on the unit).

As I said when the humidistat was on (while we were away from home for a time), when we got back the temperature in the house was way above what the thermostat was set at indicating to me that the thermostat wasn't controlling anything as there was no need for temperature control just humidity control. I assume that this is an efficiency setting.

This system has 2 distinct ways to set it 'At home', where the thermostat keeps the temp (and humidity) down, and 'Away from home' where the humidistat controls the air-con and therefore humidity. Temperature isn't so important as no-ones home. The 'Away from home' and 'At home' settings are listed on the units.

[HayZee518]

ok the a/c removes heat from a room or dwelling through an exchange of energy [heat] through the freon medium. as the gas is going through the condenser its heat is given up by action of the fan so inside heat is exhausted outside. the coolness is provided by a fan blowing air over the evaporator into the room. moisture in the air is humidty. you can have a temperature of 75 degrees and if the humidity is relatively low, say 45% you'll feel comfortable. BUT if the moisture content goes up to 85% yer gonna feel miserable. if you can find a seperate humidity control just for ha-ha's take it right out of the formula and run the system off just the thermostat. see what happens. if its integral with the thermostat then there ain't much you can do. That's why I said to find a schematic for the system and send it.

[sibleyj]

ok the a/c removes heat from a room or dwelling through an exchange of energy [heat] through the freon medium. as the gas is going through the condenser its heat is given up by action of the fan so inside heat is exhausted outside. the coolness is provided by a fan blowing air over the evaporator into the room. moisture in the air is humidty. you can have a temperature of 75 degrees and if the humidity is relatively low, say 45% you'll feel comfortable. BUT if the moisture content goes up to 85% yer gonna feel miserable. if you can find a seperate humidity control just for ha-ha's take it right out of the formula and run the system off just the thermostat. see what happens. if its integral with the thermostat then there ain't much you can do. That's why I said to find a schematic for the system and send it.

Any documentation relating to the Thermostat/Humidistat is at the house and we're out of town at the moment.

So does that mean that it is possible for humidistat to control the air-con in the 'away from home' scenario, and the thermostat to control it in the 'At home' scenario?

I'm really just trying to figure out why my electricity bill has more than tripled despite no change in conditions/settings (apart from any change of the Florida weather between June & July).

[mike n]

A C Repair

First of all you need to determine what your humidistat is doing, controlling dehumidification or a humidifier if it is dehumidification then you will need to make sure if it is a whole house dehumidifier or if it is using supply air tempering through your main system if it is you need to make sure your heat is working and if you want ot have any savings while dehumidifying with supply air tempering you need to adjust the temperature control up 75 degrees is alot of comfort range and if it is 95 outside you are running at the systems peak

[sibleyj]

First of all you need to determine what your humidistat is doing, controlling dehumidification or a humidifier if it is dehumidification then you will need to make sure if it is a whole house dehumidifier or if it is using supply air tempering through your main system if it is you need to make sure your heat is working and if you want ot have any savings while dehumidifying with supply air tempering you need to adjust the temperature control up 75 degrees is alot of comfort range and if it is 95 outside you are running at the systems peak

The humidistat is simply switching on the air-conditioning as a means to dehumidify. As I said in my first post the settings for when we are away are

Humidistat - 65%
Thermostat - COOL & 75 degrees
Fan - AUTO

It was the fact that the temperature in the house was a lot higher than 75 degrees that gave made me think that the thermostat must be bypassed in this situation. I'd have thought this was a money saving setting so that when you're away the air-con just takes care of the humidity. When you're home and the thermostat is the main control (humidistat - off) the thermostat keeps the temperature comfortable and the humidity is controlled as a result.