I live in a 20 yr old condo with 2 Heating Systems that were described as "heat pumps" and recently decided to replace the thermostats from the 24 year old controls to Honeywell RTH7600 series touch screens.

Ran into some issues as the wiring from my old thermostats didn't exactly line up with the new ones but a local contractor familiar with the building systems walked me through it over the phone and I followed his instructions to a Tee!

My problem is with the weather getting cooler, I've set the thermostats to 23C for comfort.

With one of the systems, it seems to start with nice warm heat gently blowing but then within a few seconds it seems the AC compressor kicks in and blows more moderate luke warm air. I also find that the unit comes on pretty regular to maintain this temperature (both heat and the compressor kicking in). Should this be the case?

The other unit - I can set the heat to 30C and while the element in the unit comes on the fan never engages however if I set it to 23, the unit kicks in and blows cold air.

Help :)


I really don't have much to compare it to as my old thermostats seemed inconsistent and would either bake or freeze me at their will.

Please compare the setup parameters by looking at the installation guide. One is located here.

7-Day Touchscreen Universal Programmable Thermostat RTH8500D by Honeywell - Honeywell Central

Next, see if the heat/cool flip occurs in heat and cooling modes.

If the above is true then flip the value of function item 190.

If the setups are both the same and the mode won't switch, then suspect a broken reversing valve or a bad connection on the O/B terminal.

Particularly interested in the values for the following 170, 190, and 530.

Note the troubleshooting section in the install guide.

Funny you mention the O/B because I have no wires connected there for either unit. The old unit had this mysterious "k" connection which not even the manufacturer could respond to (they got out of the residential business years back and had no support materials on their site).

For the one unit I have on -

170 is set to 4
180 is set to 1 (190 is bypassed due to the 170 setting)
530 is set to 1

My biggest fear is burning out the compressor - figuring it doesn't need to be running in the winter!

I'll post pics of the units later today.

This won't be easy. I found a gizmo that uses a terminal "K".

http://www.forwardthinking.honeywell...69_2065efs.pdf

First of all, with heat pumps, the outsde unit does operate in the winter, but not when the temperature is below 40 F or definitely below freezing.

In reality: Balance Point:
An outdoor temperature, usually between 30° F and 45° F, at which a heat pump's output exactly equals the heating needs of the home. Below the balance point, supplementary electric resistance heat is needed to maintain indoor comfort.



Emergency Heat (Supplementary Electric Heat) - The back up electric heat built into a heat pump system. The same as an auxiliary heater, except it is used exclusively as the heat source when the heat pump needs repair.

Heat pumps are wired animals and you have to determine a few things.

Hey could be a single stage heat ump with emergency heat. This puts the burden of switching modes on the homeowner. When the outside temp is above the balance point, the homeowner switches to emergency heat.

Dual stage heat pumps will use the heat pump and when the heat pump can't really produe enough heat, aux heat runs in addition to the heat pump. Sensors wired to some thermostats can force the aux heat to run when the out side temp is below the balance point. Or you can force it to run in stage 2, when your in emergency heat mode.

Dual fuel systems adds additional complications. In these systems, the heat pump and the aux heat cannot run at the same time. Ex ample. An eectric furnace and a heat pump or a gas furnace and a heat pump.

Your descriptions are bugging me a bit and some condos use variations of commercial systems. They could use fan coils with one or two pipes which are essentially chilled water systems.

You might have a central boiler and your own AC unit. These systems would not happen in a home.

I find it odd, when you said that the AC is operating in the winter. Not sure you mean blowing cold air or the outside unit is running.

Heat pumps also nned to run in the AC mode when calling for heat when the system detects that the outside coils have to defrost.

We have a lot of possible complications to sort out:
1. What kind of system do you really have
1a Single stage heat pump with emergency heat
1b. Dual stage heat pump with aux heat
1c Do you really have a heat pump at all?
2. The K terminal that no one seems to know about
2a. How many wires were at the thermostat
2a1. What was the terminal designations
3. Are their the conventional heat pump terminals in the air handler. C, W, Y, O/B, G; Separate O & B
4. Is there a gizmo in the air handler that took the conventional terminals and added a K terminal, say becaue it was do difficult to retrofit to add AC to the existing Codo at one time.
5. Did you have separate control of the FAN mode with the old stat. I suspect not, because of the K terminal.

I have are questions than answers.

In fancy stats such as the Honeywell vision pro series, you can put a sensor in the outside unit that measures the outside temp and the balance point is then selected in the thermostat.

There can be a lot of things going on here.
Most important questions:
1. # of wires at the old stat total and connected.
2. What they were connected to?
3.What terminals are at the air handler?
4. Is heat included in the condo fee?
Any info about the air handler, old stat and outside unit at all.

Condos cause all sorts of grief. They are sometimes a cross between a hotel system and a residential system. Manufactured homes may also set the mode of the system at the furnace, so can condos when they use a 1 pipe system..

I'm not sure what kind of help I can be.

Obviosly the mode is not right when it's set to heat only and you have AC.

Sorry for the late follow up

Seems weird. I leave it around 23C and had that issue but I decided to jack up the heat to 24 and now it's the heat & fan that are running only! :) Is it possible that the unit combines heat and AC for certain temps and pure heat for higher temps?

To re-iterate:

The K terminal on the
Thermostat can be used to operate both the fan and
Compressor on a single wire, and the module is designed to
Receive the signal from the K terminal, split that signal and reroute it to operate the compressor, and/or fan for normal
Operation. Use with the following thermostats:
— THX9321R
— T2060F3080

Thanks KISS - but the problem is my local guy told me to cut the K wire and hide it so its not currently hooked up.

Well, the local guy might be wrong. Buy Honeywell WireSaver Module for Prestige Thermostats - THP9045A1007 | Honeywell THP9045A1007

It sure does seem that Honeywell created an add-a-wire type of product for a particular thermostat (Pretige).

Depending on the wires you have and need, you may need to pull another cable or use something like this: FAST-STAT

It seems Honeywell is paying for the use of that patent. The guy that has that multiplexing patent is happy for sure.

Just when I thought everything was cool - we had a warm spell so I shut the system off for about 10 days (high double digits in November? Nice)

Turned it back on.. . And were back to square one. Now I'm including pics.

The first 3 pics are of the unit that I leave off - you'll see the 3 connected wires - the rest are taped up

The last 2 are the one I leave on - there's a sound I attribute to the compressor running (squeeks vs the fan that ran when it was blowing warm air only).

Let me know if you can decipher anything from these - otherwise I'll try another set of local pros.

Mmmmm. Obviously, they are not the same units. One uses 3 wires and the other uses 6.

Let's look at the top one. 3 wires. Fan, emergency are controlled from the panel. Let me also assume that they are self contained. No EXTERNAL separate unit.

If I ASSUME that these units only heat and I ASSUME the standard wire colors, it could indicate that there is 24 VAC to the thermostat then red and blue are LIKELY 24 VAC and a contact closure from R to W, turns on the unit.

Fan speed, emergency, auxiliary are are handled from the control panel.

The second unit has three additional terminals which are all the same color.

What are they for?

One possible explanation is fan speed.

So, the confusion arises because:
1. Do these heat only?
2. Any model # info or data on the web?
3. Any schematics behind the panels?

It could be a fan-coil system: Buy Honeywell TB8575A1000 SuitePro Fan Coil Thermostat - 24V - 2/4 Pipe | Honeywell TB8575A1000

So, a couple of things are in order:
1. Is this heat only?
2. What type of things can be controlled at the stat? Fan speed?
3. Any model #'s anywhere?
4. Any terminal designations anywhere (stat, unit)?
5. Can you find any links on the web?

Actually both units offer heat and cooling. The first unit does offer controls at the unit - but seems a bit archaic that if I want the fan on during heat I have to get up and turn on the fan.

The second unit is controlled by my thermostat terminal.

I've looked for model numbers and nothing on the units themselves seem to jump out as a model number.

Oh, Areyou telling me that one of the units is a slave to the other one and that you only have one thermostat in the place?

I still believe that you have Fan Coils and not heat pumps and they may behave this way:

Two pipes: Heat or Cool; with Auxiliary Heat (requires optional
pipe sensor).

Pipe sensor allows auxiliary heat to turn on when
pipes have cold water.

What does this mean? It means that there are two heat exchangers, one with hot water and one with cold. The central plant doesn't run full cold and full hot all the time because it's a waste of energy. If the water is cold, you would like to be able to run resistance heat and that's AUX Heat.

It does a misnomer to the process by calling it heat pump. There is no compressor. Just a fan and some tubes. One set hot and one set cold. It does act as a water to air heat exchanger hence they get the term heat pump.

So, in this case, one of the stray wires should go to a sensor on the pipe. The thermostat makes the call whether to use the valved hot water or reistance heat, or both when heating.

In cooling, the cold pipe is selected and everybody is happy.

Fan speed, on/off, emergency are all handled within the controls on the unit. Only whether to heat, cool and whether to use a pipe or electric heat is up to the thermostat unless it's forces to use electric heat.

The drawback, generally is the fan continuously runs. Although I did notice an AUTO fan mode on the controls.

The second unit, I believ is virtually the same with the addition of variable speed controlled by the thermostat.

THUS standard thermostats will not work in this case. Pipe temperature determines whether emergency heat runs.

In general, these type of units are suitable for hotels with setback and occupancy sensors, They are not suited for programmable thermostats.

Having the aux/emg heat in the controls could be to your advantage so that a standard heat pump termostst with some controls modifications could work EXCEPT you would not have a variable speed fan. That cuts down the noise.

Not sure what I could come up with besides the Fan Coil Thermostat.

For fun, this seems promising. http://www.cochranesupply.com/downlo...01B%20Spec.pdf

All right - so after doing some research on my own - I'm siding with you in the belief that these are fan coil units and not "heat pumps" as stated in my condo documents.

Wondering if calling in the pros does any justice here? Or should I just buy yet another thermostat?

In any event, I think you still have some digging to do even if you do decide to contact the pros.

1. Locate from the codo office info on the heat pumps for servicing assuming it's your responsibility.

2. There were numbers on the panel which could be model numbers. Contact Chromolux to see if they have any information.

3. Fan coils are relatively simple. A hot and cold coil or a single coil, a few valves and a changeover sensor (if one pipe) and a few temperature sensors.

4. With single coils, the water temperature changes based on the season, so you onley have heat in the winter and air in the summer based on the temperature in the pipe.

5. Programmability, with fan coil units is going to be difficult to find.

I did find this fan coil thermostat that appears to be programmable. The various models off er programmability and it offers a BACNET interface for building automation systems.
KMC Controls

Retrofitting will not be for the faint at heart.

Others, in your condo must have faced similar issues. The path may not be an easy one.

One thing that would make your decision easier is if heat comes out of condo fees, but then if you use less electricity/cooling loop water or heating loop water the overall bill for the complex could be lower.

With programmability, you'll have better sleep.

The problem is, is fan coil thermostats are typically used in hotel systems with an occupancy sensor.

With appropriate ducts/dampers, e.g. a re-heat coil, it's capable of de-humidifying.

Yep, it might take a pro to figure it out. You may have to run more wires t the thermostat. If you can find the documentation, all the better. There has to be a copy at the condo office. Copying might be $2.00 a square foot. Scanning might be about $10.00 total.

The only thing, I could foresee is "they don't make a programmable fan coil thermostat" because they seem to be extremely rare.

My concern would be whether a BACNET controller is REQUIRED t set them up.

So, you need to do a little more looking. How many coils? Voltages on the valves? Modulaing valves? Pipe sensors?

The thermostat may require more auxiliary parts, but it has low parts count, capable of heating, capable of cooling and capable of dehumidifying. Efficiencies have probably gone up since that unit was put in.

Were' still here to help, but find some numbers on the unit and locate whatever documantation you can find. It will make the cost lower unless it's a total replacement.

Thanks for the guidance. I'm going to contact the condo office today. I've also got a hold of the pro that gave me the wiring specs over the phone - he should be dropping by later today to hopefully give me the answers I need.

The heating fees are not part of the condo fees! Last year I paid $100/month in Electricity costs for the 3 coldest months of the year!

I'll give you the final details once this is ironed out.

Here is another ptogrammabl fan coil thermostat: http://www.docs.hvacpartners.com/idc.../33cs-56si.pdf


I'll try to look for more.

It's also possible, that ot could use cool + electric heat strips.

There seems to be a lot you don't know and age is wrapped up into this too.

You may pay to run the motor and hot/cold water comes out of your condo fees.

Any number of options:

Hot water/cold water; 2 pipe/4 pipe
Hot water and compressor
Cold water and heat strip

Good luck. It may have blown that Wallmart thermostat out of the water.

Hotels base setpoint on occupancy.
Owners, base it on schedule with overrides. Overrides are short and long therm (Vacation schedules)

Since cooling towers don't work in the winter chillers take over.

My heating schedule looks somewhat like:
Cold starting at 10:00 PM
Wake, wakes to 80 for 15 minues or so
Back to 68 util dinner.
There is a short bump here as well ad then beack to 68
This could be a water to air heatump

So, normal temps are about 68 with fee short term bumps and lowered to below 65 at night.

When humidity is high, it gets bumped manually. If going out it's easy to set override for x minutes, Vacation mode overrides longer.

Some overrides work to just the next schedule, others for the time selected.

So the contractor came by and confirmed both units are in fact heat pumps (also confirmed by the Condo Property Management). The 3 wire unit is so old, it unfortunately will not work with the full function of the thermostat (I'll have to operate the fan manually) but the thermostat does engage the heat elements when I turn up the temp (just takes about a minute).

The other unit he confirmed was engaging both the compressor and heater. He re-wired it to engage the emergency heat and not trigger the compressor (think he added a jumper at the unit level - not the thermostat). Its working as it should now - but looks like I'll be shelling out for some new units in the coming year - probably going to do one each year to maximize the home reno tax credit we get here in Ontario.

Thanks for the update. Your first paragraph mantions heat elements. What happened to the compressor? Is there one?

The second may cost you an arm and a leg to run, because your operating on resistance heating alone. Is the compressor not working at all?

FWIW: Heat pumps move heat from one place to another. When they heat, they act like an air conditioner running backwards.

With just the compressor running, this is considered stage 1 heat

The thermostat may decide that since the temperature isn't getting and hotter and I've been trying for 20 minutes, let's engage stage 2 heat.

So it combines the compressor and the heat strips together.

Some other rules:

At some outside temperature, the heat produced by the heat pump and the electric heat is the same. This is generally the point they both run at the same time.

At some other outdoor temperature, the heat pump refuses to work at all. Now everything is up to resistance heating.

Heat pumps have a defrost mode that they have to run in once in a while to keep the outdoor coils from freezing.

So, it looks like you'll be saving your pennies.

I'm hoping I don't get a crazy electricity bill as a result of this change. The compressor was running in conjunction with the fan - but the heating elements didn't seem to kick in. So their change does engage the fan and I get a nice gentle heat blowing. The change really only affects the times I'm home getting ready for work or after work - outside of that the thermostat shuts down the system. In the end it should eliminate the constant running during the day and save a bit of money.