[-Jim-]

How to make this work-Lennox Dual Fuel G61MPV-60C-091 & XPG15-042 - ComfortSense 5000

Folks,

First of all thanks for having this Forum for newbies like me to post, and get advice on HVAC questions.

I live in Metro Vancouver, B.C., Canada and Dual Fuel Heat Pump / Furnaces are starting to gain in popularity here, but most contractors are not 100% up to speed it seems. (Not one I contacted used software to calculate sizes for HVAC residential retrofit applications. I thought this a bit bizarre as I expected more science, and less "rule of thumb", on these expensive integrated systems. They use 800 square feet per ton for heat pump sizing, but then adjust down based on existing Duct work. I have no clue how they size the Furnace )

Our home is 3550 square feet total (2 story + a basement of which 550 square feet is currently unfinished, and used mostly to store stuff we'll never use again => but that's another story!). We had it built 20 years ago from a Jennish Plan, it's 2X6 on 16 inch centers with R26 in the Ceilings. I had an Energy Assessment done a month ago, and the building is still surprisingly good but a little "tight" (0.251 changes per hours versus 0.300). The heat loss for the house is 50,801 BTU's per hour @ 15.8 °F (-9°C) as is =>this reduces to 43,547 BTUs if I insulate the un-insulated portion of the basement foundation walls.

The climate here is quite moderate with the typical yearly minimum temperature of 0.9°C (in December) in my neighborhood, with the extreme minimum being -16°C (3.2 °F recorded on 12/29/1990). There are 39.4 days per years where the temperature dips below freezing (0 °C - 32 °F)

The Yearly maximum is 22.3 °C (August) and absolute maximum 34.5 °C (94.1 °F recorded on May 29, 1983) All data from Canadian National Climate Data and Information Archive. I was away Fishing in the North Pacific, but my wife and youngest son swear it go to 40+ °C last summer in August (104+ °F) for a whole week!

I purchased a Lennox Dual Fuel G61MPV-60C-091 Gas Furnace, a XPG15-042 Heat Pump, and a ComfortSense 5000 Thermostat. (All to replace my original 20 year old Airco Gas Furnace that was still operating nicely.) This system was all installed (along with a Bradford White Hot Water Tank to replace a John Wood unit that worked flawlessly since new 20 years ago as well) last Thursday (2 days ago).

I expected some decent documentation on how to run this as an integrated system, but the manuals for all 3 units don't seem to address this issue. I used to have a programmable thermostat on my old system with typical set back for sleeping and away for work. These are present on the ComfortSense 5000 and I programmed the same old set points.

But I'm wondering if doing so is worthwhile? The Heat Pump seems to be able to keep up a 21°C => 70 °F temperature all day (7°C - 45°F outside) without the G61 kicking in, but when the sleep set back (19.5°C => 67 °F occurs the thermostat turns on the G61 in the morning to bring the house back up to temperature. My brother in law, who lives a few miles away and also has a Heat Pump, keeps his at a constant temperature day and night; and his back up heat (electric in his case) never kicks in.

So is it better to keep a constant temperature 24/7 than use setbacks?

Another question is there any real benefit to having a the circulating Fan in the G61 running on slow speed 24/7? That's the way the installer left it, and said it will elliminate cool spots in the house. We find the noise somewhat distracting.

Thanks for your patience in reading my windy post.

And thanks for the assist.

 

[dandyme]

the 3 degree setback shouldn't be causing your issue


at what temp is the changeover set up for?


call your contractor and discuss your concerns with them

 

[-Jim-]

dandyme,

Thanks for the reply.

There seems to be no info on what is set where on the documentation, or on the Thermostat (that I can find). The contractor said the cut off point for the heat Pump is 1.5 °C (34.5 °F) but it didn't get that cold overnight.

I guess I'll have to call the contractor to discuss this.

I was surprised I can't easily see what heat source is running when on the Thermostat. I have to run out side and see if the Heat Pump is running as I the fan is always on in the G61 to circulate the air and I can't see the combustion area at all.

 

[dandyme]

have them make sure they configured the controller correctly.

did they not leave ALL the documentation that came with the system......YOU paid for it.

 

[-Jim-]

Gents,

It appears the issue was mostly the lack of information in the documentation. I called the vendor and they sent out their Technician to have a look. (The 3 manuals is all I'm getting it seems. Nothing that intergrates it as a system .)

The technician advises the Heat Pump locks itself out when it goes into defrost mode, and then the Gas Furnace comes on if heat is required during this cycle - but this isn't indicated on the Thermostat. So at least there is a plausible explanation for why the furnace came on at 45 °F.

As for my Brother-in-law's system, because he has Electric Back-up heat, it can run coincidentally with the Heat Pump whereas a Gas unit cannot. The Tehnician thinks my Brother-in-law probably can't even tell if the Electric Heat comes on => as it's seamless.

As far as the set-back issue goes I'm not convinced their explanation rings true. He said his tech people tell him the cost of the energy to start the heat pump is far more than the energy saved during the set-back hours. I'm a motor head (Winder Electrician - Electronics Technology Technician level - IEEE Member for a decade) with lots of experience in Industrial Applications) and I'm certain I've read an IEEE Paper on the subject sometime in the last decade or so.

I'll look for the information, but in the meantime, is this theory at work Industry wide?:eek2: Do you have an opinion on Setbacks? Is there any Data to support this (sorry, Six Sigma training kicking in...) ?

 

[pacnw]

why can't you tell?

if I remember correctly you should see the following;

heat pump only- stat should show 'Heat On""

(Heat or Auto Mode) gas heat- stat should show "Aux Heat On"

(Emerg) gas heat - stat should have red light in the right upper corner and show Aux Heat On"

depending on where the heat pump is, can you hear it by opening a window or looking out a window?

depending on where the exhaust of the furnace is, can you see the steam from the exhaust pipe?

check these out and let us know.

 

[-Jim-]

pacnw,

You are correct about the Aux Heat On indicator, so I now have a method to determine what Heat Source is on. Thanks.

I have run out of the House and around to check the Heat Pump (one looks a bit silly outside in your PJs) at times, and openning a nearby window to hear it works as well.

We have seen steam from the exhaust a couple times now (that's what triggerred our concern about the Furnace coming on at 45 °F).

 

[pacnw]

in emerg mode, I rechecked mine, and it only shows heat on with the red light in the corner on as well.

 

[westlaker]

From BC Hydro,

Thanks for contacting BC Hydro for advice on recommended temperature settings customized to your needs while at the same time considering heat pump controls.

When it comes to ideal temperature settings for stand alone heating systems such as gas or electric, BC Hydro recommends programmable thermostats set at the following settings:

● Sitting, reading or watching TV. . . . . . . . . 21°C (70°F) Sleeping. . . . . . . . . . . . . . 18°C (64°F)

● Working around the house. . . . . . . . . . . . 20°C (68°F) Away from home. . . . . . . . 16°C (61°F)

When it comes to temperature settings for heat pumps, it gets a little more complicated. Sometimes, tampering with temperature controls could cause it to deviate from optimum efficiency, causing the back-up system to switch on unnecessarily. Heat Pumps will operate most efficiently if they run continuously at constant temperature settings, during the warmest days of summer for cooling and during the coldest days for heating, thus eliminating the gas back up source which should only turn on when the temperature outside drops below -7°C. Programmable thermostats are generally not recommended for heat pumps. In its cooling mode, a heat pump operates like an air conditioner, so turning up the thermostat (either manually or with a programmable thermostat) will save energy and money. But when a heat pump is in its heating mode, setting back its thermostat can cause the unit to operate inefficiently, thereby canceling out any savings achieved by lowering the temperature setting. Maintaining a moderate setting is the most cost-effective practice. Recently, however, some companies have begun selling specially designed programmable thermostats for heat pumps, which make setting back the thermostat cost effective. These thermostats typically use special algorithms to minimize the use of backup heat systems. For more technical information on operating you heat pump effectively, I would recommend contacting your heat pump manufacturer or dealer, as they will know which settings produce optimal efficiency. In the meantime, I’m also attaching additional reading material for your reference:

http://www.bchydro.com/guides_tips/green-your-home/heating_guide/Install_A_Heat_Pump.html#

http://oee.nrcan.gc.ca/publications.../publications/infosource/pub/home/heating-heat-pump/relatedequipment.cfm?attr=4

It will be cold in the next few days so I'm expecting the backup heat will come on.

What is your Heat Pump Balance point Temperature at? Mine is at -1.

G71MPP Furnace
XP15 Heatpump
IAQ T-Stat

 

[2nu2no]

There’s a difference between heat pump termination, high pressure lock out. If the unit is locking out high pressure on defrost from the furnace and heatpump running at the same time. Lennox makes a tempering limit for the neg. side of the evap. Coil to break W, that will end the problem. Ask your contractor.

 

[-Jim-]

Gents,

Thanks for all the continuing input.

pacnw: you said "in emerg mode, I rechecked mine, and it only shows heat on with the red light in the corner on as well." I'm re-checking mine now, but the first time I tried it there was no red light in the corner when in EM Heat mode.

westlaker: I read those links before I purchased this system and that's part of reason I'm confused (more than usual). It says ASHPs can work down to -5°C (23°F) whereas my contractor (Coleman Heating) has said they set the temperature at +1.5°C to lock out the XPG15-042. At that temperature (or lower) the G61MPV provides all the heat.

So my mindset is I'm not getting the maximum savings available from the Heat Pump (nor minimizing my carbon footprint - Geenhouse Gas Emissions) as this setting seems quite arbitrary. There was zero consideration of the heat loss for the house by the contractor which is 50,801 BTU's per hour @ 15.8 °F (-9°C) as mentioned below. This value is supposedly quite good for a house of this size in this area according to the government certified Energy evaluation company who tested my house.

By the way, you mentioned yesterday you expect your back up heat to come on. Mine was already working long before the time you posted. (I left at 10 am yesterday, and returned today.) We have similar Heat Pump models, so I'd expect similar performance. (My home is in Coquitlam.) Was there any measurement / calculations done to arrive at your Heat Pump Balance point Temperature (-1°C)? Why wouldn't it be the -5°C mentioned in the BC Hydro Guide, or close to it?

As far as specially designed programmable thermostats for heat pumps, I was under the impression the ComfortSense 5000 was not only that, but one that easily handles a Dual Fuel System like mine (and yours). Is this incorrect? It offers up programable setbacks, and makes to mention of any possible negatives in doing so. So I thought that was the best way to go.

2nu2no: I don't think I understand your comment. (I'm an electrical type - not HVAC.) Can you dumb it down for me? Thanks.

pacnw: The ComfortSense 5000 cycled on the G61MPV in EM Heat Mode while I typed this, and still no Red light in the corner. I can't find any reference to a Red Light in the manual either (69-2218-02). So now I'm more confused...


Thanks for the assist Gents.

 

[westlaker]

I will have to check with the installer on how he came up with -1.5. Good point it should be closer to -7 as per hydro.

I hear you about the setbacks. I'm still trying to find out whats best.

The XP15 manual states that one should avoid frequent temperature ajustments, turning the unit off and back on before pressure equalize puts stress on the unit compressor.

My emergency heat has kicked in last night. I'm in Coquitlam as well.

 

[-Jim-]

westlaker,

I assume you mean Aux Heat came on => or maybe with your Thermostat is says EM Heat??

 

[westlaker]

I meant Aux Heat On.

 

[-Jim-]

My Installer advised the Setbacks should only be 3 or 4 °F so the Heat Pump can handle it. I've got mine 3°F cooler (70°F to 67°F at night -11 pm to 6 am => and when were are away most days 8am to 4 pm).

Does anyone have any thoughts on the furnace fan on ciculating the air at slow speed 24/7?

 

[-Jim-]

Gents,

I was over at my Brother in Laws yesterday (he's acouple miles away and has a 2 ton Lennox XPG15 with Electric supplimental heating) and it was a degree or two below 0°C (32°F) => and his unit was still running.

I asked him what his set point was, and he advised he thought it was -5°C (23°F). So now I'm more confused as I would have thought there would be a Lennox standard setting for this.

Help! :anyone:

 

[beenthere]

Balance point is determined by the homes heat loss to the heat pumps BTU output.
So it is different for each home that has a different heat loss.

 

[-Jim-]

Balance point is determined by the homes heat loss to the heat pumps BTU output.
So it is different for each home that has a different heat loss.

Thanks for the info. The heat loss for the house is 50,801 BTU's per hour @ 15.8 °F (-9°C), but I can't find anything on the Heat Pump BTU output (nameplate, or manual), or method of calculation.

Can anyone advise?:anyone:

 

[beenthere]

Ask your contractor for the BTU specs.
Or go to the AHRI website. And look at the heat ratings for 47 and 17 degrees.
And plot a graph.

 

[-Jim-]

Ask your contractor for the BTU specs.
Or go to the AHRI website. And look at the heat ratings for 47 and 17 degrees.
And plot a graph.

Thanks for the suggestion. I got more details from the Indoor Unit (CX34-43C-6F-1) and went to the AHRI Site and grabbed the following:

XPG15 DEDICATED DUAL FUEL HEAT PUMP LENNOX INDUSTRIES, INC.XPG15-042-230* CX34-43C+TDR G61MPV-60C-091

The info on this system gives High Heating 47 °F - 35600 Btu; Low Heating 17 °F 22200 Btu. (Can I assume that this is the Heating output of the Heat Pump at those temeratures and assume some liniarity between them, and beyond their endpoints if I draw a line on a graph? i.e. Assume the slope of the line is constant? )The HSPF is 8.70 and therefore the cooling costs are $298 and Heating costs are $696

(I also found a very similar XPG15 DEDICATED DUAL FUEL HEAT PUMP LENNOX INDUSTRIES, INC.XPG15-042-230/* CX34-43C +TDR+ G61MPV-60C-091 but the only difference is the "/*" after the Heat Pump Model and an increase in heating costs by $90 per year. I can't figure out what the "/*" is, does, or means.)

I assume the data from the first unit is correct. Please advise if I'm all wet. Thanks.

By the way I don't understand what a TDR is? TDR gets stuck onto the end of Inside Unit Model number at the AHRI website.

I assume the output of our XPG15 Heat Pump is sufficient to keep up with the losses from the House (50,801 BTU @ 15.8°F) or the Contractor wouldn't have selected it, but I don't know how to draw this on a graph using the BTU info from the ACHI website to obtain the Balance point.

Care to pass along any hints? :angel: