Just had Trane XL20i HP, XV95 furnace and XL950 thermostat installed - not real happy

[tigerdunes]

I am not disagreeing with previous post but it should be mentioned that it is unlikely the new HP can maintain inside temp comfort at very low temps. This is called temperature balance point where the heat loss is equal to heat gain. Probably your dealer has not made that calculation for you. If you can get down to the low 20s that would be great. Through trial and error, you can find that outside changeover temp that works best for you. Obviously, if inside temp begins to drop, then you are past that point.

IMO

[pclausen]

I will obviously want to keep my 500 gallon in-ground tank to supply the water heater, range and backup generator, but I don't see why that would necessarily make it an obvious choice to stay with the mod furnace as opposed to consider a TAM8 air handler?

Does it go below +15'F >150 hours per year?

I would say no.

Here's the historical weather data for my area:



So it rarely gets below freezing. The record lows are as follows:

Jan -10F was set in 1994
Feb 1F was set in 1996
Mar 10F was set in 1996
Apr 21F was set in 1950
Oct 26F was set in 1972
Nov 10F was set in 1950
Dec -3F was set in 1983

So they all took place more than 16 years ago. Looking back over the last few years, would that is it rare for there to be temps consistently below 25 degrees for days, let alone below 15.

[pclausen]

How was the Load Calc actually used in sizing the equipment?

For cooling, the above calc shows needing 3.5 ton, so I think the 2/4 ton XL20i is the proper size.

For heating, the model currently installed is 80,000 BTU, but dual stage, so the first stage is 49,500 BTU, which is likely all that would ever be needed. The smallest XV95 furnace is 37,700/58,000 BTU, the the fan is only designed to move enough air to support a 3 ton outdoor unit. At least that is what the guy told me was the reason for going with the TUH2B080A9V4VA furnace model.

On the modulating furnace, the only model that supports a 4 ton outdoor unit, is the 100,000 BTU model.

On the TAM8, I noticed there is an option to add a hydronic heat kit. I wonder if that would be a good combo with my 94% efficient Polaris water heater which is sitting right next to the furnace anyway?

[tigerdunes]

The reason I think it's obvious is because even with the air handler as opposed to mod furnace, you will still need the propane fuel and the tank.

I would want to see the operational BTU cost of the propane versus electric heat strips.

IMO

[energy star]

I to thought five degrees was low as a design temp.

[pclausen]

I would want to see the operational BTU cost of the propane versus electric heat strips.

What would I need to determine that besides the LP cost of $3.13/gal and electricity cost of $ 0.089/kWh?

[tigerdunes]

What would I need to determine that besides the LP cost of $3.13/gal and electricity cost of $ 0.089/kWh?

These results are from a fuel comparison calculator that I like to use. Plugging in your costs which I will assume are accurate and all inclusive, I used a COP of 3 for the HP and 95% eff for propane furnace.

Here are the results and should be used as a guide only.

Cost per 100,000 btu of useable heat

Electric baseboard: $2.37
Heat pump: $0.88
Propane: $3.60

Obviously straight electric without the HP condenser is substantially less than propane.

One thought though concerns your generator capacity. Obviously the propane furnace would not take much power to use compared to an air handler with heat strips and HP condenser. Someone would need to put the numbers to the paper not to mention other appliances like refrigerator that you would want to run.

Just some thoughts to take into consideration.

IMO

[pclausen]

Wow, it would seem that propane is not at all the way to go for generating heat in my situation! Yes, the figures I gave were all inclusive and reflect the total amount I pay for each energy type by unit.

If I'm understanding the results correctly, a TAM8 air handler with electric heat strips would be a more efficient solution given my energy costs. I guess I should also look at replacing that Polaris water heater with an all electric unit. Or am I missing something?

I have a load shedding transfer switch on the generator, so I'm not too concerned about burst in energy consumption that heat strips would result in, as long at they won't consume more than 10kw for extended periods.

[tigerdunes]

I would think you would require at a minimum 15 KW in heat strips that should be staged. That would yield about 51 KBTUs provided from heat strips alone.

You need to understand your generator's capacity to handle all the appliances including HVAC. I would call the installing dealer for your generator to make certain your generator's capacity is adequate for what you plan on running. Not certain it is.

IMO

[pclausen]

I have 400A service coming into my house. One 200A panel it tied directly to the utility meter base, the other goes through a 200A transfer switch. Looking at the installation manual for the 15Kw heating module for the TAM8, it appears to be feed via one 40A one 20A 240V circuit. So I can have them wire the 40A circuit to the panel feed by the transfer switch, and the 20A to the panel not protected by the generator. This way, during a power outage, I'd loose the 3rd 5kw stage, but stages 1 and 2 would work fine.

I'll consult the generator installer/electrician to make sure, and also with the Trane installers to make sure the air handler doesn't do something stupid like shutting down all the way if it senses no utility power on the 3rd heating element.

The more I think about it, the more I feel a TAM8 air handler is the way to go over the modulating furnace. I have already asked the installer to quote me for the TAM8. I can't imagine that it would cost more than the modulating furnace, even with the 15kw heat strips.

That cost per 100,000 BTU of usable heat has been a real eye opener for me. I'm very surprised the sales rep did not ask me about my energy costs and just assumed going with another propane furnace was the most energy cost effective way to go. It appears to clearly not be.

We were about to get a new dryer and I was leaning towards paying the extra $80 for the gas model over the electric, I guess I need to reconsider that as well.

[tigerdunes]

Defintely an electric dryer as long as you have panel capacity. In fact I would suggest weaning yourself off propane as is economically feasible with goal of only the propane fueled generator.

With that said, I still remain concerned about generator's capacity and suggest this be thoroughly researched with all appliances including HVAC before deciding on TAM8 air handler with electric backup heat strips. Dealer will need to help you with heat strip size recommendation.

In other words, cover your bases.

I would also want to know the pressure on electric rates where you live. No doubt though you have a great deal of economic leverage with electric versus propane.

IMO

[catmanacman]

you could go with a tam8 air handler and hot water coil plumbed to your polaris for auxilary and emergency heat,also remember most hvac companys sell you whats best for them not you

[pclausen]

Going the hot water route would certainly eliminate any electrical concerns with the generator.

I'm still a little scared about the cost of heating water using propane given the cost figures presented above.

I wonder if the ultimate in efficiency would be to get a hybrid (heat pump based) water heater once the polaris gives up the ghost? I wonder if such a unit would be able to keep up with the demands of a TAM8 water heat coil?

Being that emergency heat will hopefully only be used on rare occasions, perhaps the hot water coil would be the most practical solution?

I'll discuss both the electric and hot water coil options with the dealer tomorrow. You guys have been great and I feel much more informed now than before. I should have posted *before* going with the current solution, but I'm very glad they are willing to change out what I have right now. The tam8 might be stretch, but maybe not if they have to disconnect the line-set from the coil anyway to swap out the furnace. From my measuring, the line set will not need to be extended to be connected to the tam8 since a plenum pedestal is needed below it anyway for the return. The tam8 sure would make for a lot cleaner looking setup.

[tigerdunes]

Please followup with whole house media filter cabinet and additional return.

Good Luck
IMO

[pclausen]

Thanks. I'll be sure to do that. I'm keeping my fingers crossed that a tam8 + heat strips is less expensive than a XC95m + coil and that the budget will then allow for adding another return and media filter. I know price discussion is not allowed, but a hint as to which is more expensive would be appreciated as I negotiate with them tomorrow.

I found a fuel cost calculator at purdue.edu. This ones includes an adjustment to be made to the HSPF based on location. For me, the closest city is Richmond, VA, and the adjust is to change the HSPF rating from 9.0 to 7.6.

The numbers I then get to generate 100,00 btu of heat are:

$1.171 Heat Pump
$2.608 Heat Strip
$3.607 Propane

So heat pump is still the obvious choice for primary heat and electric for backup as opposed to propane. It seems that the only reason propane would make sense is during an extended power outage where having an alternate local source of energy could be advantageous.

Another interesting bit of data the purdue calculator has, is that the ASHRAE design temp for Richmond, VA is 18F, not the 5F they used.

[mechanical'al]

the supply runs are two close to the end of the trunk .
the way trunk systems work is off back pressure.the air should hit the end of the trunk and pressurize it. with runs at the end as in the pics it cant build pressure . a simple fix would be to add an 18" long piece of trunk to the end . Then all supply runs could recieve equal pressure or as needed some could be dampered down such as small load rooms baths ect.

ps this looks like a comon install still only 1 pipe , as is likely why the didnt add the second on the new change out it was easy to just go with what was there

[tlj000]

I to thought five degrees was low as a design temp.

Manual J design temp for central VA. should be 17-19 for heating and 90 for cooling.
You can tell on the manual J report that the design temps were changed by the fact that the font is in bold type.

There could be a justified reason for this, I don't know your area well enough to say for sure. There is a reasonable possibility your equipment is still over sized.

With that small return and restrictive filter, it's unlikely that the system could actually deliver 4 ton of cooling.

[pclausen]

I didn't get a chance to talk to my rep yesterday as he was on vacation. I'll get with him tomorrow. I'll be sure to discuss the restricted return with him, and also see is he can add an extension at the end of the supply run to allow pressure to build up.

Looking at the run history from yesterday and the day before, I was wondering if it is normal for the heat pump to be running 60-70 percent daily to maintain 71/72 degrees inside, when the temp is in the 30's outside?



I have the propane furnace set to not come on at all unless it gets below 20 outside, but I was curious if it is normal for a heat pump to run almost constantly when temps are in the 30s outside. If temps drop into the 20s for a full day or more, based on what I'm seeing now, it will mean that the heat pump will run for 24 hours straight.

Maybe there's more to this than just the cost to generate 100,000 btu of heat? Even though propane is more expensive, if it can deliver that heat in short intense bursts, perhaps that is more economical than having a heat pump droning away all day everyday in the winter time?

I'm having a hard time deciding if a TAM8 is better or worse than a propane fired furnace, in my situation...

[beenthere]

I didn't get a chance to talk to my rep yesterday as he was on vacation. I'll get with him tomorrow. I'll be sure to discuss the restricted return with him, and also see is he can add an extension at the end of the supply run to allow pressure to build up.

Looking at the run history from yesterday and the day before, I was wondering if it is normal for the heat pump to be running 60-70 percent daily to maintain 71/72 degrees inside, when the temp is in the 30's outside?



I have the propane furnace set to not come on at all unless it gets below 20 outside, but I was curious if it is normal for a heat pump to run almost constantly when temps are in the 30s outside. If temps drop into the 20s for a full day or more, based on what I'm seeing now, it will mean that the heat pump will run for 24 hours straight.

Maybe there's more to this than just the cost to generate 100,000 btu of heat? Even though propane is more expensive, if it can deliver that heat in short intense bursts, perhaps that is more economical than having a heat pump droning away all day everyday in the winter time?

I'm having a hard time deciding if a TAM8 is better or worse than a propane fired furnace, in my situation...

Short intense burst are what makes people uncomfortable, and then they usually turn the set temp higher and get a higher heating bill.

The Heat pump won't run all day every day.

[dan sw fl]

I didn't get a chance to talk to my rep yesterday as he was on vacation. I'll get with him tomorrow.

Looking at the run history from yesterday and the day before, I was wondering if it is normal for the heat pump to be running 60-70 percent daily to maintain 71/72 degrees inside, when the temp is in the 30's outside?

I have the propane furnace set to not come on at all unless it gets below 20 outside,
but I was curious if it is normal for a heat pump to run almost constantly when temps are in the 30s outside.

If temps drop into the 20s for a full day or more, based on what I'm seeing now,
it will mean that the heat pump will run for 24 hours straight.

Maybe there's more to this than just the cost to generate 100,000 btu of heat? Even though propane is more expensive,
if it can deliver that heat in short intense bursts, perhaps that is more economical than having a heat pump droning away all day everyday in the winter time?

I'm having a hard time deciding if a TAM8 is better or
worse than a propane fired furnace, in my situation...

IF you mean you wi$h to pay a LOT MORE to provide your share of support for the Propane industry,
increase the cross-over point { but, only if your hard earned $$$s are burning a hole in your pocket}.

You may soon find out when it's 22'F outside for > 6 hours, if the heat pump is able to maintain > 70'F.
However, Mother Nature may be on your side the whole winter and it may not go below 24'F.

THE MOST ECONOMICAL operation is the Heat Pump, BY FAR.

I would be looking at ALL alternatives NOT to use Any propane.
--- including letting the house temperature slide a few degrees for a few days in the winter.