I recently purchased a home with a geothermal heat pump (ap049) model an there is no thermostat. I purchased a 5/2 day programmable one and gave it my best shot at wiring it based on how the wires are hooked up to the system itself. When I put the batteries in I lost all my power to the system. I don't have any of my little flashing/steady lights anymore. I have 240v going into the coil and zero coming out. I assume I have to replace the coil, however I need to know how to correctly wire the thermostat before I replace it. Any and all help would be outstanding as it is getting hot here in va bch. Lol.

nice to have you ask but I think most of folks will turn and tell you to pick up a technician to get a few of about 05 or 6 variables answer for I service call

couple questions might be raised as to why a programmable thermostat so much if you're in real cold weather sometimes you don't want the backup 8 to ever come on if you don't force it to come on by different stage temperatures

It sounds like you let the factory-installed smoke out of the control voltage transformer.

It isn't a major repair, but you need to know what each control signal wire does. Lethal voltages and high pressures lurk within...you have only scratched the surface of potential damage to the system.

Consider calling a pro.

I've been busy so didn't catch this sooner.
While I concur that it sounds as though you are already over your head, you likely did little more than blow a small fuse on the circuit board.
The question is why, and that is likely because you do not understand what each of the signal wires are for and likely crossed R and C at your new thermostat.
If you can sort them out you may still be able to do this yourself.

That's what I'm trying to do. I was hoping someone would
Have the same system and tell me how theirs was wired

That's probably closer to the truth than my earlier remark

A lot of the builder grade code min systems we deal with between geo jobs lack niceties such as a control transformer protection fuse.

If by "coil" 88k53 is in fact referring to the control power xformers output leads exhibiting 0 Volts, then maybe there is no protection fuse, or the transformer laid down its life to protect the fuse.

Let me ask a dumb question for the pros.....why would an HVAC system be installed 'without' a thermostat?

Posted By robinnc on 23 May 2012 10:24 PM
...why would an HVAC system be installed 'without' a thermostat?

If this was an existing home and the prior owner purchased a premium thermostat system with bells and whistles, I can see the homeowner taking the thermostat with them when they sold the house.  That said, I would have put something in its place.

If purchased today, our thermostat system (for one of our two geothermal units) would cost about $500, not including installation. 

Posted By 88koller56 on 18 May 2012 01:53 PM
When I put the batteries in I lost all my power to the system.

Was the thermostat working prior to the batteries being inserted?  Any chance the battery polarity was reversed when inserted?

Also, with some thermostat designs, there are pins on the back of the main body of the thermostat that "mate" to the thermostat base on the wall.  If your design is similar, you may want to check for bent pins and proper alignment.

hey 88k53....Joe and Engineer are great pros and have you on the right track....but can you give us the make/model of the thermostat you purchased?

Do you know how many stages of heating and cooling the thermostat you have will control? You likely need a "3H/2C" model if you have a two-stage heat pump with backup electric heat.

Without any more info, I kinda wonder if you've bought a battery-powered programmable thermostat that can't make use of the 24v "R" wire to power the thermostat. (that's how the old NOMA programmable thermostat on my old furnace worked....had to change the AA batteries every year or so or the thermostat and the furnace stopped running).

Thanks geome.....hadn't thought about that! I would have never thought someone would actually steal the thermostat when they sold the house! I had wondered if I had missed some really new technology somewhere like running everything thru your pc and have wireless sensors placed around the house!

Posted By robinnc on 24 May 2012 11:18 PM
Thanks geome.....hadn't thought about that! I would have never thought someone would actually steal the thermostat when they sold the house! I had wondered if I had missed some really new technology somewhere like running everything thru your pc and have wireless sensors placed around the house!

Lots of thermostats can work with remote sensors and can be controlled with Ipads or smart phone apps.

It is a Honeywell rth6350d 5/2 day

Thermostat manual is here:
http://customer.honeywell.com/techlit/pdf/PackedLit/69-2696ES.pdf

If you connected the "R" wire from your heat pump to "R" on the thermostat and "C" from the heat pump to "Rc" on the thermostat and left the factory-installed jumper in place between "R" and "Rc" on the thermostat, that could trip the fuse on the control circuit transformer in the heat pump as the pros have suggested. I see that the manual for the stat says "Do not use C, X or B. Wrap bare end of wire with electrical tape."

But, you should also note that page 11 says this:
"This thermostat works on 24 volt or 750 mV systems. It will NOT work on multi-stage heat pump systems or 120/240 Volt systems."

The stat seems to support a single stage heat pump with backup electric aux/emerg heat. I suspect you'll want to take this stat back and get one that supports the right number of stages for your heat pump (likely 3H/2C if you have electric aux/ backup coils in your system). You may not be able to get a suitable stat on the shelf at your local big-box hardware store and may have to check with either local HVAC supply houses or online suppliers. (I know that my local HD store only has up to 2H/2C stats on the shelf).

Agree need 3H / 2C if system has aux strip heat. Need thermostat that controls y2.Most wholesalers won't sell to the public

Pexsupply.com is a possible online source.

With all wires disconnected check for 24 Vac between red and blue

Is my heat system multi stage

Posted By 88koller56 on 28 May 2012 02:04 PM
Is my heat system multi stage

The FHP’s AP Series water to air heat pump is the result of almost 40 years research and development experience in the US geothermal market. The AP Series is an incredibly energy efficient heat pump that can lower your energy bills and provide you with the cost savings and the comfort you expect from FHP. Rated as the most efficient product on the market today, the AP Series unit features a state of the art twostage unloading scroll compressor. When controlled by a multistage thermostat, this compressor matches the demand for heating and cooling. This can mean up to 70% savings in your energy bill, while improving humidity control and the overall comfort throughout your office. FHP’s AP series will help you attain the highest LEED points for Geothermal installations.



Yes

So what kind of thermostat should I be using?

Any 3 stage heating / 2 stage cooling thermostat. Honeywell 8321 is used widely.

You need a thermostat that can control a heat pump with 3 stages of heating and two stages of cooling (3H/2C) Often this functionality is found in manufacturers higher-end programmable touch-screen thermostats that will typically cost upwards of $150. Examples would be a Honeywell 8320 or a White Rogers 1F95.

While you might not be comfortable with opening up the service panel on your heat pump (and yes, there are potentially lethal voltages lurking inside the cabinet)....generally you'll need a replacement thermostat that has connectors on it for all the wires that are currently attached to the "thermostat connections" block on the control board on page 4 of this document: http://www.fhp-mfg.com/files/download/APSeries_IOM_REV1_12.pdf.

Typically that will be at least : R,C, Y1, Y2, O, W, G for starters. If your unit has backup/aux electric heat strips, you might also need W1 and maybe even W2.

Note that besides hooking up the right wires once you get a suitable thermostat, you'll also need to program it for the right settings for your heat pump. The new thermostat likely will not just work out of box by plugging in all the wires. It isn't terribly difficult to program the thermostat...you'll just need to study the manuals for both the thermostat and heat pump. But if that isn't your idea of a fun way to spend an evening, you may want to find a reputable HVAC service company to do the job.

The highest thermostat failure rate I ever had was during the relatively short time I used Luxpros.
John enough about Hydrotemp already.