How to make sense of the choices? Thread split off.

[BadgerBoiler MN]

Every heating/cooling appliance must be properly sized to the load. The load is properly determined by performing a Manual 'J' heat load. Furnaces with higher cooling loads will require higher blower speeds - while in cooling mode - but they make furnaces with multiple speeds; one low fan-on, one heating; a bit higher, and one for cooling; typically the highest speed. Then of course there are variable speed ECM fans burners or less expense two-stage furnaces.

Once you have the heat load the duct work can be addressed. It does pay to look at the whole system before starting. There is no excuse for installing heating equipment more than 150% of the heat load or for that matter installing any piece of heating equipment without performing a manual 'J' first. This is how the homeowner should determine which furnace to choose.

It is the dealer not the furnace.

[54regcab]

BadgerBoiler MN, what we run into in the south is trying find a furnace with enough blower capacity for cooling, but without oversizing on the heat side. Some manufacturers don't offer their nicer furnaces in sizes under 60K. No manufacturer that I can think of offers a 80% furnace 50k or under with a variable speed blower. The VS feature is nice for those of us in the south, and it's not cold long enough to justify the cost of a 90%+ furnace.

[BadgerBoiler MN]

Point taken. But here in the north country when we face small heating loads we size for cooling and put a cased coil in the plenum and drive it with the water heater.

[54regcab]

Using the water heater/coil for small loads works great. For some reason they aren't popular around here so local suppliers don't stock them. I've seen the concept online, but haven't found a good source/manufacturer for a residential product. Firstco makes them as part of the air handler. IEC which is in Oklahoma City manufacturers them, but they focus on commercial. My wife used to work there and got a unit that they were using for testing purposes once they were done with it.

[BadgerBoiler MN]

Yes. First Co. makes nearly every size of coil both single and pumped packages.

[RoBoTeq]

BadgerBoiler MN, what we run into in the south is trying find a furnace with enough blower capacity for cooling, but without oversizing on the heat side. Some manufacturers don't offer their nicer furnaces in sizes under 60K. No manufacturer that I can think of offers a 80% furnace 50k or under with a variable speed blower. The VS feature is nice for those of us in the south, and it's not cold long enough to justify the cost of a 90%+ furnace.

Now you are just fabricating specifics to complain about. Why are you looking specifically for an "80%" furnace "under" 50K with a variable speed blower? Are all of the houses in OK City under 1,000 square foot bungalows? You keep pinpointing specific applications where it is difficult to obtain the specific furnace you want to complain about. What is wrong with working in a positive manner with what is available? As I have stated before, you seem to just want to dwell on something to complain about HVAC professionals. Just what is it you do that you feel you work in the HVAC industry? You have already posted an entire thread telling us how you DIYed in a cooling system to an existing oversized heating system. Just what is it you do that is HVAC related on a daily basis?

[RoBoTeq]

There are dozens of hot water coil manufacturer's in North America. Multi coil, USA coil, Diversified etc. And there are plenty of hydronic air handlers as well; Rheem, ADP, Goodman etc. I did hydronic coil heating for certain applications for decades in the Baltimore/DC corridor, and I'm getting more and more HVAC contractors, especially those with a plumbing background, to do more of them in PA.

In fact, I don't have it operational yet, but I have a hydronic coil in the supply plenum of my own home heat pump that will eventually be connected to a tankless LP hot water system.

[54regcab]

There are dozens of hot water coil manufacturer's in North America. Multi coil, USA coil, Diversified etc. And there are plenty of hydronic air handlers as well; Rheem, ADP, Goodman etc. I did hydronic coil heating for certain applications for decades in the Baltimore/DC corridor, and I'm getting more and more HVAC contractors, especially those with a plumbing background, to do more of them in PA.



In fact, I don't have it operational yet, but I have a hydronic coil in the supply plenum of my own home heat pump that will eventually be connected to a tankless LP hot water system.

I'm glad to see the hydronic coils are becoming more popular, and you are promoting them. Have you done any systems that use multiple air handlers? On your setup will the water heater be doing your domestic hot water also?

[Mr Bill]

Why are you looking specifically for an "80%" furnace "under" 50K with a variable speed blower? Are all of the houses in OK City under 1,000 square foot bungalows?.

I think he is talking about the typical home in his neighborhood.

[54regcab]

Now you are just fabricating specifics to complain about. Why are you looking specifically for an "80%" furnace "under" 50K with a variable speed blower? Are all of the houses in OK City under 1,000 square foot bungalows? You keep pinpointing specific applications where it is difficult to obtain the specific furnace you want to complain about. What is wrong with working in a positive manner with what is available? As I have stated before, you seem to just want to dwell on something to complain about HVAC professionals. Just what is it you do that you feel you work in the HVAC industry? You have already posted an entire thread telling us how you DIYed in a cooling system to an existing oversized heating system. Just what is it you do that is HVAC related on a daily basis?

I would have like to have one of those furnaces for my own 1600sqft house. 50k isn't just for small houses, it can serve over 2,000sqft IF it's insulated right. Ask any of the building science guys about this one. Gas around here is cheap (less than 50 cents per therm), so anything over 80% doesn't have a reasonable payback time. The variable speed feature is mostly for comfort reasons, even though the payback time on that is long.

In a daily basis I work with the Smarthours project. We install the Smarthours thermostats and run service calls when the customers call in if it doesn't work correctly. We don't repair the HVAC units or install new ones as part of this project, we just determine if the problem is with the thermostat or HVAC unit. As part of the project we see the good, bad, and the ugly as far as installs go. Some installs are excellent, others are so bad we don't even do the thermostat install for liability reasons. Most are in-between.

Since our thermostats are system powered they go blank when a furnace shuts off on high limit, and then we get a service call. People are quick to blame our thermostat because the old battery power stat it replaced just let the furnace cycle on high limit and the customer didn't know the burners were switching off because warm air continued to come out of the vents and the thermostat "stayed on". Since the furnace is often oversized to begin with the house still stayed warm even though the burners were shut off on high limit 1/2 the time. After seeing a bunch of these through the winter it does give me prejudice to the combination over-sizing of furnaces and poor ductwork design.

[54regcab]

I think he is talking about the typical home in his neighborhood.

We get plenty of jobs that are on houses not much better than this. Not fun, but a paycheck is a paycheck...

[Mr Bill]

Since our thermostats are system powered they go blank when a furnace shuts off on high limit, and then we get a service call. People are quick to blame our thermostat.

What brand/age of unit are you talking about that the "high limit" kills the power to the stat? all the high limit does on any newer "board type" unit is break the circuit back to the board, the lugs on the board receive direct power from the thermostat.

[Mr Bill]

What brand/age of unit are you talking about that the "high limit" kills the power to the stat? all the high limit does on any newer "board type" unit is break the circuit back to the board, the lugs on the board receive direct power from the thermostat. .

Edit: I said the lugs on the board receive direct power from the thermostat, correction, the lugs are powered directly from the transformer, and the thermostat is powered from the lugs, so the high limit would not effect power to the stat.