Does having a variable speed fan on a single stage unit cause extended unit run time and thus on an open loop system cause the demand for more water from your well to go up ? Possibly more efficient but causing more water usage.?
No. single speed unit runs as long as is necessary to satisfy the thermostat set point. Same water usage would occur regardless of fan type in heat pump. Variable speed fans are typically "ECM" fan types which are inherently more efficient than "PSC" fan types at the same speed. My guess is the only reason you can get variable speed fans in a single speed unit is to capitalize on the fan type efficiency (ECM vs PSC). I doubt you get the ability to actually set and use multiple fan speeds with a single stage unit. You probably have the ability to raise and lower the actual speed the fan runs at via a setting but not the ability to run multiple fan speeds during heating or cooling. This would depend on manufacturer too.
Thanks, that may be why they put a bigger rated fan in, then it jus runs slower. I've been debating on miami heat pumps 2.5. Vs 3 ton. The 3 just has much bigger fan rating. Compressor is 2 higher but fan is 4.
typically fan sizing is based on what the equipment manufacturer thinks it will need to combat the pressure loss in the duct system. as the tonnage of a unit goes up, so does the likelyhood that said unit gets used in an ever larger duct system. (2 ton units don't end up heating/cooling 3000sq ft as an example). the manufacturer makes a wildly oversized and inaccurate guess about the flow resistance in the ductwork that a particular unit will see and upsizes the fan motor for it. so typically fan motors are oversized for all but very restrictive ductwork (those people need new ducts or a bigger fan or both). so that is one way a variable speed fan could be used with a single stage unit to turn down or up the fan speed depending on the actual installed ductwork pressure loss that the fan is subjected to. This requires the installer to actually measure and adjust for these things during the install (commissioning as its called). good installers do this; most installers of HVAC equipment aren't good. YMMV
Well, being I am a DIYer.. i dont have the equipment to figure that out. (So, I'm a Bad installer)I'm just replacing an old florida em031 hp. Where there listed numbers fall between the 2.5 and 3 ton miami heat pump. The price difference is negligable, both are under 3k. And its bassically, unhook the old, slide the new in and crank it up. The cooling is listed as 2 btu bigher and the heat is 4 less. Where the 3 ton is 4 higher cooling and 2 higher heating. Plus the new Miami's have variable fans. I know it's pretty much all relative. I suppose I should probably just go with the 2.5, and if it's just not enough... get the 3t. Not like it will cost me 10-15 k to replace.
no, you wouldn't be a bad installer. I meant the people who do this work for a living, have the tools (and presumably have the knowledge) but don't commission because it takes time and money without explaining the benefit to the user of the system. the fact that you are on here asking questions makes you already better than 99% of the population. You seem curious enough, want to go down the rabbit hole and do a load calc on your house: coolcalc.com Coolcalc will tell you your heating and cooling loads so the unit can be properly sized (assuming the inputs are correct). Its very easy to use. It is often that existing air conditioning equipment is way oversized leading to short cycling and resultant no dehumidification. An especially problematic situation for single stage equipment.
I need to play with this coolcalc, it seems at this point I must have missed some things as it has my heating at 48 and cooling at 24. It never asked for the insulation in my attic or let me adjust the walls for more than 8 for brick. Plus.. dont even try this on a smart phone... need a mouse pointer . To trace the house and then it was still a couple hundred to big. I will try again. But this is excellent. Thank you !
Let's try this question... on a hot day 95 degrees and sunny. How often would you expect your hp to run. And for how long... just ballparking a well insulated house and a right sized unit. Would it be 15 on and 15 off. Kind of balanced ? I'll see what mine is doing this week as it will hit 95 for a couple days. I'm expecting 15 on and 10 off. Coolcalc is still giving me 24 cool and 38 heat. I would think that would be reversed.
Can anyone answer??...Lol My well insulated house 1920 sg ft, with a 3 ton 2 stage water to air unit, so 1st stage is about 2 tons. Never goes into stage 2 unless I force it. Unit runs for 2 + hrs off for 1 1/2 + hrs. Slow fan speed, LAT high 40's F early in the season low 50's
ChrisJ has it right - no feasible way to answer. Theoretically, in a cooling climate (ie somewhere south), afternoon on the design cooling day (ie ASHRAE 1% day), and a single stage system sized to perfectly match your house's BTU/hr heat gain on the design day, I would expect a single stage piece of equipment to run continuously with its output keeping pace with the heat gain. At any other time period, it will run less than continuous (ie it will be oversized because it is sized for that one day). How much further you are away from the conditions I just noted, the less it will run and the more on/off cycles that will occur. Most houses have shockingly oversized equipment even for the single day they are supposed to be designed for. As a for instance, I need like 3 tons of cooling for my house but closer to 6 for heating. My house's original ac units were combined 6 tons - so originally oversized by a factor of 2 on the design day. For the other time periods the system was probably more like 3, 4, 5 times oversized (the basic conundrum with single stage equipment). You basically get no dehumidification with the 10 to 15 minute on/off cycles because the coil doesn't get cold enough/long enough. I know you are on an open loop and your well is a concern, but if you can figure out a way to use dual or variable speed equipment, its night/day for interior comfort compared with single stage equipment. (ignoring the obvious energy efficiency benefits)
Yes, i knew it was kind of a dumb question... and I would not want a continuous running system. Currently my house runs pretty consistently at 40 %. And I do cycle on and off a lot. Pulling a lot of water from my well would be a concern. Being in SC I cool a lot more than I heat. It's hard to trust anyone that is trying to sell you something to give you what you really need. I'll probably just stick with another 2 1/2 ton single stage. I always thought my current hp ran to long in the summer so I was thinking I might need to upsize. But i did just add another r30 to the attic. So we will see how that effects it.
Open loop is a different animal. I was fascinated by a guy’s open loop that some how used the vacuum created by the water falling down the return well to help draw the water up out of the supply well. Probably physics or something.....Lol
sounds like a siphon with outgoing water pulling up incoming water in perpetual motion. guess you would still need some mechanism to get it started but once going... i'm never going to tell anyone not to insulate better but for an already insulated home, more insulation has diminishing returns. If its easy and cheap to install, then by all means do it but unless you have an uninsulated, ballon-framed Victorian more insulation in an already insulated cavity probably doesn't make a noticeable difference. What typically is the downfall of most energy efficiency schemes is not paying equal attention to air movement (convection) as is paid to the insulation (conduction). Radiant is the only other way that energy moves and is a distant third to conduction and convection. Air sealing at the attic ceiling plane and basement/crawl space plane are as equally valuable as the insulation there.
Well, the blown cellulose had settled down to about 4 inches.. so it definatly needed some help. They were suppose to air seal it too. How well they did remains to be seen. Basement is allready plastic wrapped sealed. I would like some better venting in the attic.. have the soffits and ridge vent now.. but it still gets darned hot up there. Also had new reflective shingles put on.. so it should all be of some help. As you said..never get my money back..but I feel better about making it better.
