Modulating HVAC Question (Air Cond.)

[Buzz]

Has anyone had experience with or have a modulating HVAC system? How do you like it? We need to get our two units replaced and I like the idea on paper, especially here in the Phoenix area where they run 24/7 for 6 months of the year.

 

[Dusty Stevens]

I have the latest and greatest best you can buy. Not sure what a modulating unit is but mine is variable speed on compressor and inside air handler. It has been over 100deg here for at least a month every day and here is my usage in a 4br 2500ft sq brick house with tall ceilings

 

[Buzz]

Thanks. I think that’s what they call modulating. Supposedly it holds temp within 1% and runs at about 35% capacity nearly all of the time. We had a dual stage on our last house that was nice, but I think it ran on high a lot more than was advertised. Is yours quieter than your old unit? I hate hearing the forced air noise in the house.

 

[hoz53]

Thanks. I think that’s what they call modulating. Supposedly it holds temp within 1% and runs at about 35% capacity nearly all of the time. We had a dual stage on our last house that was nice, but I think it ran on high a lot more than was advertised. Is yours quieter than your old unit? I hate hearing the forced air noise in the house.

I imagine in Phoenix this would be a heat pump mabie with some electric backup? Alot of the air noise comes from the size of the duct work. A forced air system can be designed so you can barely hear it run.

 

[rijndael]

.We had a dual stage on our last house that was nice, but I think it ran on high a lot more than was advertised..

This is a somewhat complicated topic, but it can be normal. You need a unit that is sized properly for your space. You do this with a Manual J calculation. You really don't want the unit to kick in, cool it down quickly, and shut off. This is what you get when you oversize a single stage unit. This can lead to high indoor humidity levels.

Indoor humidity has a pretty big impact on the 'feel' of a room. 45% humidity at 73F feels a lot cooler than 60% humidity at 73F. The benefits of full variable state units come when you want energy savings and humidity control. Running for extended periods at a low % of total capacity gives humidity control.

You also need to be mindful that you can have multiple stages to your outdoor compressor and that doesn't necessarily correlate to what your indoor fan is doing. It can sound like it's "on high", but that doesn't tell you what's going on at the compressor/condenser.

 

[B Nettesheim]

We put them in all the time at work, they are quiet, work well, and the customers love them!

 

[47WillysGuy]

We had rooms of different temps with old 17 year old unit and it was replaced about two summers ago with a Trane A/C (heat pump type). House now is at a constant temp and humidity (50%).

I had A/C guys install these filter unit that takes this filter:
Lennox X6675 MERV 16 Media Air Cleaner, 1 Count (Pack of 1)Lennox X6675 MERV 16 Media Air Cleaner

Brand	Lennox
Item Dimensions LxWxH	25 x 20 x 16 inches

This air cleaner will last us a full year and does away with the ceiling air filter which have to been replaced 3-6 months.

 

[PopCharlie]

I have 2 of these units in my house. One set for upstairs, one set for downstairs. They run at about 35% compressor speed most of the time. They keep the temperature within 2 degrees of set on the thermostat. The thermostats are like tablets hanging on the wall. Wifi connected etc.
They are very efficient. My electric bill for June was $178. It rarely goes over $200. This is for a 5400 Sq ft home in Central Virginia.
As a side note, 7 years ago, I replaced every light bulb in my house with LED bulbs. This made a huge difference in my electric bill. Plus, I have had to replace only 2 bulbs in the last 7 years.

PopCharlie

 

[Buzz]

Thanks everyone. Both companies that have come out so far seem to think the ductwork was designed to produce higher velocity air to deal with the combination of high ceilings and large rooms, which makes me feel better that there was at least some thought that went into it, but I still think these new units can get the job done without all of the racket. After doing some more research and reading the feedback here, I think we’re going to go ahead and get them installed. The quotes have been a little eye-popping, but so is the price of everything else right now.

 

[rijndael]

Both companies that have come out so far seem to think the ductwork was designed to produce higher velocity air to deal with the combination of high ceilings and large rooms

Are they guessing or is someone calculating/measuring things, like static pressure numbers?

 

[Ledd Slinger]

I had a modulating gas furnace in my last house. It was very quiet and efficient. Only downside is that none of the smart home thermostats will work with the modulating units because they cannot control proportional valves or variable speed motor drives. But if you don’t care about the smart home stuff then they are great.

Of course that was a while back for me (few years) and technology could have changed by now and there may be thermostats for them that can integrate into a smart home system. There’s new wifi thermostats coming out all the time and systems like “Ring” are allowing integration of new items all the time

 

[Dou8leD]

love the Bosch system, installed many of them and customers always call and say their electric bill has decreased and are very happy with the performance

 

[Buzz]

I had a modulating gas furnace in my last house. It was very quiet and efficient. Only downside is that none of the smart home thermostats will work with the modulating units because they cannot control proportional valves or variable speed motor drives. But if you don’t care about the smart home stuff then they are great.

Of course that was a while back for me (few years) and technology could have changed by now and there may be thermostats for them that can integrate into a smart home system. There’s new wifi thermostats coming out all the time and systems like “Ring” are allowing integration of new items all the time

These are wifi connected touchscreen interfaces that I’m sure aren’t as fancy as others. We have the nest thermostats now and had ecobee before, but the “learning” features have been more of an annoyance than anything. All I really care about is being able to control the temperature remotely so I can have the house cool when we come back from the cabin.

 

[Dusty Stevens]

These are wifi connected touchscreen interfaces that I’m sure aren’t as fancy as others. We have the nest thermostats now and had ecobee before, but the “learning” features have been more of an annoyance than anything. All I really care about is being able to control the temperature remotely so I can have the house cool when we come back from the cabin.

I have the nest and it took about a year to turn all that off but its good to go now