Is 2 stage HP nessesary w/2 stage furn

[mopar guy]

Hi everybody, this is an awesome forum for a research junkie like me. I have spent the last several weeks reading a lot of threads, before posting something I haven't found an answer too. I sure have learned a lot & had some good questions for contractors when getting an estimate.
I live in Northern Ohio, about an hour South of Cleveland & am looking at purchasing a Lennox G61MPV-60D-135 furnace with a XP19 or XP13 heat pump. Since we only use a/c for about 3 months or so here, is it nessesary for a 2 stage h/p? I'm not really worried about a bit of a temp swing with a single stage unit. I'm also reading on here that a high SEER rating is not nessesary either for being this far North. The contractor is coming tomorrow to do the Manual J (the only one willing to) & I was wondering what your opinions are.

Again, thanks for providing such a good site!
Keith

[BaldLoonie]

I think 2 stage super SEER units are overkill in cooler states like Ohio. I'm right next door. Often the high SEER doesn't mean high HSPF which is your winter efficiency. I'd look towards 12-13 SEER max for this area. You won't have comfort issues, just don't oversize the furnace or the heat pump. Make sure your dealer uses a dual fuel control that gives you 3 stages of heat if you get a 2 stage gas backup. More comfort than letting the timer in the furnace stage the fire.

[RoBoTeq]

Well, depends on your terminology. A heat pump system is by nature "two stage" in that it operates strictly as a heat pump in the first stage and with auxiliary electric heaters or uses a fossil fuel furnace instead of for the second stage.

With a fossil fuel, dual fuel set up, you may or may not require a two stage function depending on whether or not you are utilizing an outdoor themostat.

If you are referring to a heat pump that itself operates on two stages, a high and a low stage, then no, it is not required. A single stage heat pump is perfectly fine when used with a two stage gas furnace.

[mopar guy]

Thanks for the reply BaldLoonie. :) From some other posts on here, I kind of got that impression. I'll look at the HSPF numbers then as a better comparison. One question - is the dual fuel control a seperate unit from the thermostat? I'm also watching the thread on the Lennox Signiture stat vs a Vision Pro.

[mopar guy]

Originally posted by RoBoTeq
Well, depends on your terminology. A heat pump system is by nature "two stage" in that it operates strictly as a heat pump in the first stage and with auxiliary electric heaters or uses a fossil fuel furnace instead of for the second stage.

With a fossil fuel, dual fuel set up, you may or may not require a two stage function depending on whether or not you are utilizing an outdoor themostat.

If you are referring to a heat pump that itself operates on two stages, a high and a low stage, then no, it is not required. A single stage heat pump is perfectly fine when used with a two stage gas furnace.

I'm going dual fuel with a gas furnace. I was referring to a 2 stage heat pump with low/high operation.

[ksspartan]

Baldloonie..........Is a two stage heat pump overkill in Kansas City???

[RoBoTeq]

I don't see where a two stage heat pump is overkill. They are designed for added comfort, not capacity or efficiency.

[ksspartan]

So a two stage compressor doesn't buy me any efficiency? I was assuming if I ran at 2.5 tons on a 4 ton compressor that I would be gaining efficiency during low load conditions? Is the comfort obtained using a two stage compressor worth the money?

[BaldLoonie]

The real high SEER stuff is 2 stage. Either Trane's dual comp or the unloading scroll others use. So yes, buying one of them buys you SEER. In much of the country with mild summers and good electric rates, you won't get your money back in energy savings. OK, so they could deliver some extra comfort. But most people are very happy with a properly sized single stage A/C. If humidity control is an issue, get a variable speed blower with dehumidify on demand. Even in steamy weather, my house stays good on humidity with the slow ramp up of the blower, I'm not using a humidistat to slow the blower. So what would I get for spending ooodles more for 2 stage cooling? I sure don't see it and I buy for under wholesale if I want one! So hard to say what the definition of overkill is :D A lot of money for little benefit? But if budget is no object...

Many homes have moisture issues in mild weather when there isn't call for cooling. OK, a 2 stage unit running more on low could help but many have a high sensible on low which doesn't suck a lot of moisture. Better off would be a large dehumidifier like a Thermastor or Aprilaire. If your house is on a basement, put one of them down there and the whole house will immediately dry out.

For Mopar, the Vision Pro thermostat and others will do your dual fuel controlling. The Vision Pro will not do 2 stage gas backup. White-Rodgers has a model that does, I looked it up for another thread, I think it was the 1F95-391.

[hvac r us 2]

It is possible I live in the same town as mopar guy, and I am now using a two stage heat pump and dual fuel. I actually have 4 stages of heat, best investment I have ever made.

[amickracing]

You do get more SEER with a 2 stage... here's the fine print though. Of course the 2 stage units are always the higher SEER units (16 and 18).

But I was also told that the SEER rating for a 16 SEER heat pump running on the low stage could be 17 or 18 SEER, while running on hi stage it could be 14 or 15. They average the numbers to get the SEER rating they stamp on the plate. I didn't get exact numbers on how much the SEER rating differs on low an high, I was told it's not a lot, but it is definately different.

[ksspartan]

HVAC r us 2 - Which stat are you using to get 4 stages. Is it the White Rogers Stat that was mentioned earlier in this thread?

[docholiday]

What city.... I grew up in Wooster.

[hvac r us 2]

I am using Carrier Comfort Zone II. With Carrier equipment there are several ways to achieve 4 stages of heat...does not have to be all done by the thermostat. But Carriers Thermidistat can do 4 stages of heat.

Doc, I am just a little east of Akron...you were south of me by about 30 miles.

[docholiday]

Not you, I know where you live :D
..... I was talking about mopar

[mopar guy]

Originally posted by docholiday
Not you, I know where you live :D
..... I was talking about mopar


LOL Yes, I do live in Wooster. Just outside of town.

So as I figured, a 2 stage unit would be more for comfort than practicality or efficiency in my case.

[mopar guy]

The contractor I plan on using was over tonight to do a manual J on my house. That is really interesting. I got complimented for doing my research & having a good idea of what I wanted & needed. His estimate on the furnace size was right on the money & was a half ton high for the h/p. I figured 2 1/2 ton by going by what others I asked have in their homes & I was right. It called for a 2.25 ton system, so we went with a 2 1/2 ton, 15 seer, single stage h/p. With the rebate on the Signature series units, it came out to be the same price as a 13 seer Elite unit w/no rebate. Hopefully this will all fly & we can get this put in.

Thank you to all who take the time to give their knowlage & advise to this board. I do the same on some car boards. (former auto tech) This does a great deal to help all of us that want to be educated on what we are planning on buying. I'll post back later if I get this system put in, with some before & after pictures.

[ksspartan]

Mopar Guy, we must be tracking together on this. Did you go with the HPXB15 heat pump. Did you go with the G61MPV high efficiency furnace? Given this combination did you go with the Signature Stat? With three steps of heat available you should be covered with two stages of gas heat and the other stage being the heat pump. You will also be able to take advantage of the humidity control available with the variable speed blower.

[ksspartan]

As I mentioned I am taking BaldLoonies advice and shying away from the two stage compressorized heat pump. I presently have a 3.5 ton HVAC unit that is taxed on a 100 degree day in KC. I was planning to go to a 4 ton unit knowing I had the two stage compressor. Will this 1/2 ton cause me to be oversized and have potential humidity problems?

[mopar guy]

Originally posted by ksspartan
Mopar Guy, we must be tracking together on this. Did you go with the HPXB15 heat pump. Did you go with the G61MPV high efficiency furnace? Given this combination did you go with the Signature Stat? With three steps of heat available you should be covered with two stages of gas heat and the other stage being the heat pump. You will also be able to take advantage of the humidity control available with the variable speed blower.

Yes, it looks like we're on the same page. :D I'm going with those two units as there is a rebate on both & the Signature stat. Yes, I'm going with the Signature stat, along with their 4" media filter & a new Aprilair humidifier. I wanted the Pure Air system but it's way overpriced (IMO), plus, it's expensive to maintain each year. My contractor has used all of this in his house & the last house he had & says with this set up, I'm better off with the Signature stat over the Vision Pro because of the same resaons you mentioned in the other post. I think I'll be pretty happy with this set up as it will fill my needs.

Oh, BTW, have you had a Manaul J done on your place? If not, get it done before you go any further! That's the BEST advice on this board. It saved me from being almost 1 ton oversized. Offer to pay for it as I did & he was more than willing to do it. Since I'm going with him, he waived the fee for doing it.

[Edited by mopar guy on 10-20-2005 at 09:00 AM]

[ksspartan]

What do you mean by a Pure Aire System? Is this a Lennox system or another manufacturer? Why does it require more maintinance?

Thanks for the advice on the Manual J. I think the first contractor that gave me a bid did one but he did it all by hand. I thought you needed a computer to do it? I will request that the contractor I am talking to on this Lennox system do one for me.

[mopar guy]

I don't know if it's made by someone else. You need to change the UV bulbs, the catalyist & filter once which is about $400. I just felt it was to pricey.

He didn't do one then. I had all the measurments for all the rooms in my house & it took about 45 mins to do. Believe me, it was worth it.

[ksspartan]

Originally posted by BaldLoonie
I think 2 stage super SEER units are overkill in cooler states like Ohio. I'm right next door. Often the high SEER doesn't mean high HSPF which is your winter efficiency. I'd look towards 12-13 SEER max for this area. You won't have comfort issues, just don't oversize the furnace or the heat pump. Make sure your dealer uses a dual fuel control that gives you 3 stages of heat if you get a 2 stage gas backup. More comfort than letting the timer in the furnace stage the fire.

In states like Missouri does it make sense to oversize a heat pump, and install a two stage compressor that will typically always run only in the first stage during the cooling season and get the most capacity out of the heat pump during the winter? I don't want to get too fancy here and oversize my system so if the answer is to size the unit for the cooling season and get as much "free heat" out of the heat pump during the heating season I will go that way as I plan to use a dual source anyway (gas or electric).

[wyounger]

I wouldn't use a two stage unit as justification for oversizing. The ductwork probably won't like it, and with such low electric rates, the extra cost of the two stage unit won't pay for itself.

Going from 3.5 to 4 tons isn't a huge difference. Depending on the condition and installation of the old unit, though, you may not be getting 3.5 tons out of it. Furthermore the manufacturers don't hit these capacity ratings spot-on... they round to half tons but in the end the capacities don't come out as tidy as you might think.

What do you mean when you say that the system is "taxed" by 100 degree heat? Outside of the desert states, all air conditioners should run nonstop around the clock, or almost around the clock, in 100 degree weather. If they don't, it's a sure sign of oversizing, which results in inferior comfort and efficiency. Proper sizing builds in some recognition that there might be a couple days out of the year where you can't hold your temperature setpoint; you may slip a degree or two in the peak heat of the afternoon. If you add capacity so that you can always hold your setpoint no matter what, you end up with a really oversized system.

What it boils down is that once you the Manual J load calculation, you correct for the way equipment capacity is rated at 80 degrees (most people want it to be more like 75, which derates equipment capacity). At that point, you have a BTU value, and you select a system that matches that cooling load. There are very few cases that justify fudging on the numbers, and I just don't see this as being one.

[ksspartan]

If you go two stage variable speed you have the ability to slow down the fan speed on a system that is "slightly" oversized to reduce the cooling capacity and hence remove more moisture. I totally understand what your saying though that you have to be careful not to oversize your system. People that don't understand HVAC don't understand that biggger is not always better for the reasons you stated.

[me]

If you like fast hot heat on cold days, you can use a gas furnace with a heat pump and have an outdoor thermostat that will cause the call to go to gas if the temp drops below a set point.

[ksspartan]

I finally got my new Lennox system installed. I am having thermostat problems. How do you like your new Signature Stat? Then contractor installed a Vision Pro and were having problems with it doing what I want it to do.

Did you set it up to control the two stages of heat pump operation (compressor stages) plus 1 stage of furnace operation as your emergency? In other words in the furnace mode the furnace controls the staging of the heat? From what I understand this accounts for the three stages of heat available at the stat.

From a cooling perspective did you set it up to have the two stages of compressor operated by the stat?

[mopar guy]

Originally posted by ksspartan
I finally got my new Lennox system installed. I am having thermostat problems. How do you like your new Signature Stat? Then contractor installed a Vision Pro and were having problems with it doing what I want it to do.

Did you set it up to control the two stages of heat pump operation (compressor stages) plus 1 stage of furnace operation as your emergency? In other words in the furnace mode the furnace controls the staging of the heat? From what I understand this accounts for the three stages of heat available at the stat.

From a cooling perspective did you set it up to have the two stages of compressor operated by the stat?

I have mine in too. I'm not sure if your posting to me or someone else. Either way, I love the Signature stat. It seems worth the money to me. Easy to navigate compared to the Honeywell I had before. It works together with the h/p & furnace as a system. It's neat to be able to set high & low humidity levels from the stat & it controls the humidifier. :)

I went with a single stage h/p per Baldloonie's advise. It made sense to me & even the guy installing it agreed. Mine's set up for 3 stages of heat with the h/p being first, low fire & then high fire on the furnace.

I am having a problem with it at the moment. The h/p only runs for a few minutes & then shuts off. The high pressure line starts to buzz pretty bad before it shuts off, indicating to me it has high head pressure, so I locked it out. What my contractor found out was that he needs to put a larger A coil in with this model heat pump. Apparently it's to restrictive or something. Anyway, they'll be here Friday to put the larger one in so I can get it running. So far, we both love the furnace! It's so quiet & the low blower speed sure makes it nicer. No more "blast furnace" effect like our old one. :D

[ksspartan]

Thanks for the reply Mopar Guy. I was looking for you went I wrote my reply. We really have been tracking together on this one. I also have an undersized coil which is causing my heat pump to trip out on high pressure. I am also having a new coil installed on Friday.

On your Signature Stat you are able to set a high and low balance point. The way I understand it the when the temperature is above the high balance point the heat pump operates and the furnace pump is locked out. In this state the heat pump runs with its own internal controls and in my case sequences the compressor operation. Below the low balance point the furnace will run and the heat pump is locked out. In this state the furnace operates with the staging with it own internal controls. Between the high and low balance points both the furnace and the heat pump operate withe heat pump as the lead. In this state Y1 operates the heat pump and Y2 operates the furnace. I think this is as detailed as you can get with the thermostat controlling the actual stages on the furnace or the heat pump. Let me know if I'm missing something. I had the Lennox rep out the other day and thats the way he explained it to me.

I am also very happy with the variable speed motor operation. Keep me posted on how your new coil works out and I will do the same.

[mopar guy]

I thought it might be me you were talking to. :) Well, I'm glad I'm not the only one with this problem. My contractor has three like this & mine will be the experiment. When he called to order a coil for mine, they wanted him to put a 4 ton coil in it (instead of a 3.5 ton that he was originally told) with a 2.5 ton h/p. I'll guess I'll find out how it works on Friday! Lennox claims they made the change in their engineering manual last year but nobody seems to know it - even the regional manager. Go figure... LOL

As for the thermostat - yes, it has both points that are setable. Mine's set for 40º for the upper & zero for the lower right now. That's the contractors recomendation. He did take the time to explain it to me, so that was good. I'll post a few before & after pics of it next week.

[ksspartan]

I got my new coil in and my heat pump works like a charm. I had them replace the VP stat with the Signature Stat and I'm so glad I did. The Signature Stat is definitely the way to go with the systems we purchased.

[mopar guy]

Great! Glad you like it. They were here today putting in the new A coil & I was asking about that. He said there is a couple of different models of the VP & you would need the better model to get those features. He also said it was more money than a Sig Stat. I see your other post about it now. Hope it works out for you.

FYI - The larger A coil did fix my problem. Now the HP runs quiet. I have only one problem left that cropped up today. My furnace won't fire when the HP won't keep up. I believe it's a setting in the stat that's wrong but I'm not sure. I'll have to call them tomorrow. Did yours get fixed?

[ksspartan]

Even the better models of the VP can't do all that the Lennox Signature Stat can do. For example the abilitity to set the low and high balance points is not available on the VP's. I see this as a good feature to have the ability to run your heat pump between the low and high balance points until you can't keep up and then automatically kick in your furnace. I guess this is the feature that don't work on yours at the present time. It hasn't gotten cold enough here in KC yet to where my heat pump hasn't been able to keep up so I will keep my fingers crossed that mine works.

You mentioned noise and that yours got quieter. That would be my only complaint. The unit outdoors doesn't seem to be noisy but I get quite a bit of noise from the refrigerant lines in the basement. My contractor claims this is normal? Do you get much noise from your lines sets? The contractor told me that this is the compressor noise transmitted through the lines.

[ksspartan]

Mopar Guy, You might check to make sure theres a jumper between W1/E and W2 @ the stat. This may be your problem.

[mopar guy]

My line set was very loud before. You could here the refrigerant pulsating in the lines & it sounded like a rattle. Plus, the compressor short cycled & was off awhile between cycles. All that is gone but I still hear a humming when the hp is on. Nothing very annoying. The outdoor unit is super quiet.

[mopar guy]

Originally posted by ksspartan
Mopar Guy, You might check to make sure theres a jumper between W1/E and W2 @ the stat. This may be your problem.

I just checked that & I'll bet your right. :D They're not jumped in the stat & I don't see them jumped in the furnace. I already have a call into them & awiating a call back, so I'll mention that. I'll bet he made a mistake when he wired it. I'll keep you posted. Thanks!

[ksspartan]

Should be jumped in the stat not the furnace according to my set up.

[mopar guy]

After I read thru some of the paperwork, that doesn't appy to mine. I have the 81M28 stat (as you should) & to install a jumper wire, it only applies to the 81M26 stat. I messed around with it, trying different things & ended up putting the settings back & so far it's working. I won't be sure though until it calls for backup. The service guy called me today & is going to call Lennox Monday. He thinks the stat is bad. I guess we'll wait & see.... :) Thanks again! I'll keep you posted.

Did you get your A coil replaced??

[mopar guy]

Originally posted by ksspartan
Mopar Guy, You might check to make sure theres a jumper between W1/E and W2 @ the stat. This may be your problem.

I read those instructions myself & the way it's worded, it shouldn't apply to my stat - but it does. They came out with another stat & it did the same thing. They double checked the wiring & it was fine. Then the service guy remembered that jumper from another job but it wasn't a gas furnace. They tried it & it works fine. He said they had taken some sort of repair manual with them & it doesn't show that in there. They tried to jump it in the furnace first & it wouldn't work but when they jumped them in the stat, it works perfect now. So far, this is an awesome system. If it saves me some money like I think it should, that's a bonus to the comfort I'm getting with it. The heat pump has been taking care of the house with low's in the low 30's, so that's going to help with the gas bill. :D

Is yours working well for you?

[ksspartan]

Great to hear Mopar Guy. I do allot of design work with Lennox Technical Support so I asked them to send me the wiring diagram for my system using the Signature Stat and it showed this jumper in a dual fuel applicaiton so I was surprised to hear you didn't need it. I'm glad to hear your now happy with your system.

I got my new A-Frame coil installed and have the stat wired according to the diagram I described above. I am very happy with the way the system operates. My only complaint is the pinging noise that seems to come from the line sets. I'm not sure if this is something I am going to have to get used to or not??

[mopar guy]

I get more of a humming thru the system with the heat pump running. I don't have a basement, so my furnace is located in the laundry room, just off the kitchen. Our bedroom is above both & I can hear it at times. I might add some insulation to the second story floor to help dampen the noise. The one thing that does bug me, is the high pitched squeel coming from the humidifier valve. I might have them look into it & see if there is something that can be changed to quiet it down. Other than that, it functions beautiful. My wife even commented this mornimg on how nice the house feels now compaired to the old system. It's 20º out here now. Brrrrrrrrrr.

[ksspartan]

I figured out why my refrigerant lines were making so much noise. Temperatures in Kansas City finally reached the high twenties and my heat pump went out on high head pressure. The contractor put the gauges on and my system and it was overcharged. He removed some of the freon and the system is running much quieter with much less refrigerant noise. I still get a slight hum which I consider normal.

[mopar guy]

I've run into something else that you might want to be aware of. I would hear my lines rattle & the compressor would really dim the lights on start up but only once in a while. As I watched it, I found that after the furnace would shut off, the heat pump would start up right after. The head pressure had to be really high with the superheating of the A coil with the furnace on. My contractor said to change the 1st stage differential from 1º to 2-3º. (It's in the User section) So far that seems to have fixed it. Just getter her fine tuned now. ;)