Thoughts on new furnace??

[countysat]

I am currently receiving Furnace and A/C quotes to replace a 25 year old system. Today I was quoted on a York TM9X60 Single Stage 60,000 BTU High Effeciency Furnace with a DC blower motor. The quote was packaged with a TCGF24 A/C , a 5" media filter and a S1THEC programmable thermostat. The quote comes from a reputable dealer.
My house is a 1920's plaster and slat build, roughly 1800 sq/ft including basement, with little or no insulation in the walls and basement and minimal in the attic.
The heating and cooling replacement will eat up most of my budget so upgrading the insulation may have to wait a year or two.
I asked about a two stage furnace and the dealer said I would not make the price difference back in savings with gaining only a 1% increase in effeciency between the 2 units.
Would a single stage unit be suitable in this situation or I would be better off with a 2 stage furnace that Lennox and Carrier has quoted?
The single stage is about $1000 cheaper to the next lowest quote.

[txv]

Where are you located?

In most of the country, 60k BTUs isn't going to adequately heat 1800 sq ft. with no wall/minimal attic insulation in extremely cold weather.

Edit: It should be fine - I missed the "including basement part"

If you size the furnace for the house as is, it will be grossly oversized once the upgrades are completed. Also, A 80-100k BTU input furnace will probably be very noisy on the existing duct system. (Today's mid and high efficiency furnaces move 30-50% more air than their conventional counterparts)

If the existing furnace is functional, hold off on the HVAC upgrades and put the money towards insulation and draft proofing. There are generous grants available for blown in insulation and draft proofing can be cost effective.

If the walls aren't framed and you aren't willing to gut them, adding insulation won't be practical. (unless you get it done on the outside)

Also, a dedicated grounded circuit will be required - new wiring might be necessary.

The single stage is about $1000 cheaper to the next lowest quote.

Staging is for comfort, not efficiency; however, a 2-stage or modulating furnace may allow you to set the t-stat lower, yet still be comfortable.

The multi-stage furnaces come with true variable speed blowers which ramp up to maintain airflow as conditions change (Ex: filter gets dirty); they can also be set up with controls to reduce airflow and remove more humidity in cooling mode.

*Variable speed and multi-speed are not the same. Multi-speed high efficiency motors are available.

$1000 difference -> the contractors you're comparing may not be of equal quality.

[thewatcher]

we had a Lennox G71MPP-36C-090 furnace and a Honeywell Pro6000 installed last spring - temps weren't that cool at night at the time - I had the thermostat set for 21 @ 8am, and it was hitting that temp at the set time

last night got a bit cooler than it has been, and it was almost 9:30am before the thermostat hit 21 - it was my understanding that the system "learns" how soon it has to come on in order to hit the set temp at the set time - so did it have to "re-learn" last night because it was cooler? though I don't think it should have taken so long to hit 21 - and I also don't think it comes on in high mode

is it possible the dip switches aren't set properly? since it took so long to hit 21 after it should have, I'm worried about how long it will take when the temps start dropping at night to minus 15 - 20

[txv]

Adaptive recovery is rarely accurate from my experience.

If the furnace isn't going into high fire during recovery, either the t-stat was left on default settings or it was miswired.

[wgauci]

As TXV points out, Adaptive recovery isn't as accurate as it should be. Most stats really don't learn anything, they just take the average recovery time of the last few days to figure out how long it's going to take to recover the next day. Large variations in outdoor temps can mess up the timing. The best way to avoid this is to use a thermostat that incorperates an outdoor sensor. Most of the higher end Honeywells and other brands allow for a thermistor you can install outside, the stat will then take that value into account when allowing for recovery time.

Have your system checked out, if there's one thing this site has proven, there are a lot of people who have had multi stage furnaces installed that weren't commisioned properly or the stats set.

[txv]

Interesting. I always thought that the outdoor sensor is only useful for dual fuel or HP applications when you want to lock out a heatpump below a certain outdoor temp.

Adaptive recovery likes to cycle the equipment and bring up the temp gradually (from experience) - I'm no fan of that since cycling reduces equipment lifespan and efficiency.

[birdman325]

Looking for some help. In the process of building a new home. Basement, main floor, second floor and then a loft with a bedroom and playroom area. Planning on using a boiler system for heating and domestic hot water, as well as radiant heat in the basement. Any thoughts on the following proposal?

Lennox hot water fan coils model CBWMV (2 units)
Lennox 13 SEER air conditioners model XC13 (2 units)
Nortec Steam humidifier
Aprilaire humidifier
Pleated Air filters (2 units)
Programmable thermostats (2 units)

Heat source will be 2 Weil-McLain CGi-6 boilers

[txv]

If the house is built tightly and the boiler is direct vent/high efficiency (as it should be), you won't require the humidifiers.

Make sure that the contractor does a load calculation using the plans.

I just looked up the CGi-6 and it's only 84% AFUE, non condensing, combustion air from inside. It is in your best interest to get a direct vent high efficiency condensing model. (Such as http://www.weil-mclain.com/en/our-pr...-series-3.aspx)

Why two boilers?

Ask for more specific info - sizes, t-stat model numbers, etc.

[birdman325]

I had a similar question on the efficiency rating and I have asked and currently waiting for an answer.
The house is proposed to be a fairly good size and I think the thinking is that to run the raidant heat in the basement, heat for the entire house and the domestic hot water, 2 boilers would better serve.

[txv]

Using two boilers will just drive up the cost.

300 000+ BTUs per hour residential boilers are available. (Provided that you're not building a 6000 sq ft+ mansion, a single unit will suffice) The entire design of your HVAC system must be based on a room by room load calculation - do not allow the contractor to use silly rules of thumb.

It might be cheaper to use forced air furnaces and a single tankless water heater/boiler combo (two separate loops) for domestic hot water and radiant heat in the basement.

Zoning a single forced air system* (multi-stage equipment required) may give you satisfactory results at a fraction of the cost.

*Whether a fan coil or furnace is used

[birdman325]

Heard back from one guy with a quote to upgrade the boilers to the ultra condensing boilers (but need to get clarity on exactly which model) for an upcharge of $9,950.

[thewatcher]

Adaptive recovery is rarely accurate from my experience.


what do you normally do then, disable it?


If the furnace isn't going into high fire during recovery, either the t-stat was left on default settings or it was miswired.


any specific setting that shouldn't be on default? I'm trying to get as much info as I can so I'm prepared when I go talk to the company that installed everything.

[txv]

Each t-stat is different so I can't tell you which settings need to be changed.

Yes, I disabled intelligent recovery and just set it up to turn on the heat a couple of hours earlier.

[txv]

Heard back from one guy with a quote to upgrade the boilers to the ultra condensing boilers (but need to get clarity on exactly which model) for an upcharge of $9,950.

High eff furnaces will be much cheaper than boilers.

If there must be two boilers, I would consider design alternatives to bring down the cost. (See previous posts)

Fan coils really have no advantage over furnaces if venting is practical; there are tankless water heaters available which can also provide radiant heat. The need for circulating pumps can actually increase energy costs over conventional systems.

Did any of the contractors do a load calculation? (it's essential for new construction)

[thewatcher]

Each t-stat is different so I can't tell you which settings need to be changed.


One last question, if you don't mind - the thermostat is a Honeywell Focus Pro 6000, model TH6220D1010 - I went into the installer setup to check the settings - in the manual it shows default settings of 5 for both the stage 1 and stage 2 heat cycle rates - which the manual says is for "gas or oil furnaces of less than 90% efficiency" - since the G71 is higher than 90% efficiency, I looked at the other choices and saw it says a setting of 3 for "hot water systems and furnaces of over 90% efficiency" (underlining is in the manual)

does this mean the setting for each of the stage 1 and stage 2 cycle rates should be 3, and not the default of 5?

looking through the installer setup on the thermostat, I saw the setting for the stage 1 heat cycle (which is set at the default of 5), but there is no setting for the stage 2 heat cycle - it doesn't come up as I cycle through the settings - it should be there, shouldn't it? since it doesn't show up, does this mean something is not wired correctly?

thanks. this should help me in my quest, should something be amiss with the stage 2 option not being there


edit to add: I decided to give the "installer system test" a whirl - did the heating test - according to the manual, once in the heating system test mode, the status can be changed from 0 (heat and fan turned off) to 1 (stage 1 heat turned on) and then to 2 (stage 2 heat turned on) - but the only options I get are 0 and 1 - nothing for stage 2

I'm by no means a furnace person, so I could be way off here, but all this is telling me that as far as the thermostat is concerned, the furnace is only 1 stage, since it gives me no options to make any kind of changes for stage 2 - am I right?