|03-24-10, 01:03 AM||#1|
Will it Work?
An ASHP, ductless/inverter, 18000-24000btu. Mitsu., Sanyo, Fujitsu, or cheap China knockoff. The name brands have better documentation of performance. The cheap ones don't always match their claims. Understandable, their instructions (some) are pretty ???? .
Maybe it's just their conversion, they start with kw and go to btu for the USA, and then seer/eer/hspf/cop, and then mess it up. I don't know. The rest of the world just rates output in kw. kw out/kw in=cop---easy to do.
Elko, Nevada. 7000-8000HDD. I have a LPG castiron stove, 30k, always been enough. However, at $3.10/gal., 80%eff. = $400+ a month. A fill was $875.
I have used 30 gal since Jan. 8, it is cheaper to use electric.
I tried 2 portable ASHP 9k each, one hosers. No good. OK heat output, but pulling a vacuum to do it?? HA HA Got my $850 back from WM and picked up 4 $22 oil filled units. Have used them before elsewhere.
They work fine, 60-63f IAT, 44kwh/d, I would like: Better looks, more heat, less kwh/d, and no frown from the wife, when she visits. Yea, it is alot, its called keeping your job, 2 homes, family, 300mi apart, on a budget.
If I go with a cheapo I'll probably hack it before winter. Some sort of direct contact/earth or solar water assist or earth tube or ?? My basement is open for radient, just don't have the time now. I have 5 acres, 70% complete house I built alone, from dirt up. Full basement, 900sf a floor stacked direct except the MBR.
I think I'm looking at a unit that needs to deliver 12-15k btu as low as 5f, below that I'll need some backup. It gets to -25f and less, but low 20's day and 0's night are more common. It's 22f right now, about 50f high today. Heating (attempting) with ASHP is probably nuts, I've done worse things.
They make some mighty claims with operation down to 15,5,0, did I see below 0 claims??? Will it puke its guts out if a son/wife pokes the start at -5/-10f.
I'll almost never use the A/C, just the heater function.
Will it Work??
Thanks in Advance, feel free to beat on me, I'm used to it
|03-24-10, 11:56 AM||#2|
Join Date: Feb 2010
Thanked 3 Times in 3 Posts
Daikin cold weather test
Since I'm new to EcoRenovator I can't post links yet. If you go to youtube and search for "Daikin cold weather test" there is a video by rwsmith72 that shows just how well these units can do in the cold. What impressed me was when I looked up the specs of model used in the video at ahridirectory.org, it's a good performing unit, but Daikin makes even higher rated ones.
ahridirectory.org is a great website to compare tested performance ratings of different manufacturers. You can compare the BTU output of different models at the tested 17°F low heat output.
Hope this helps,
|03-24-10, 03:00 PM||#3|
Join Date: Feb 2009
Location: Woburn, MA
Thanked 244 Times in 224 Posts
"Heating (attempting) with ASHP is probably nuts"..
That's what I was thinking, until I looked at the City Data for my town..
25degF average low in Jan isn't that all that cold..
Elko, Nevada isn't too bad, with an average low of about 24degF.
Boise looks good too. 23degF in Jan is the coldest (on average).
Climate in Boise, Idaho
I think you might have enough spare heat in the air to get some good BTUh out of it.
And on those really cold mornings, just go to the back-up until the sun
warms things up.
My Sanyo did a pretty good job down around 20 degrees and it wasn't
even working right.
And of course, it uses such a small amount of power when it's coasting,
our heating cost for Dec was a lot lower than I expected.
If my replacement unit comes in soon, I'll be able to save some heating oil
for the rest of this heating season anyways..
Anyways, ASHP always needs a backup heater (everything actually needs
some kind of backup).
It's a bit of a compromise, not to have the HP working on -2 degree mornings,
and have to go to the backup. But when you compare the install cost
(and even the hardware cost) of a GSHP, the mini-split shines..
One other trade-off is snow. When the snow is really coming down,
when it's really getting cold, I tried to switch over to oil and avoid ice on the coil..
When the heavy snow stops, it was right back on..
Since I've got the hybrid capability, I can open the check-valve on my
main hot-water loop and run the oil at a very low BTU level.
Not burning enough oil to keep us warm with it's 4 or 5 degrees outside,
but, just enough to allow the Sanyo to coast at low power..
Both of them loafing along together can keep it toasty..
|04-08-10, 03:59 PM||#4|
Join Date: Mar 2010
Thanked 1 Time in 1 Post
I've been lurking here for awhile, reading all these heat pump threads. They are all very interesting and highly detailed with an immense amount of useful information. I'd like to thank all the contributors for their work
As an engineer, I'm very interested in heat pump technology myself. I've spent the past 2 years getting more and more involved with it.
We had a York ASHP put into our home in central NH about 2 years ago to supplement the home's propane furnace. Its a dual-fuel set up. I think alot of people (not including this forum) misunderstand ASHPs and think they don't work when it gets cold out I even got some comments like this from some of the HVAC people I spoke to when we were looking into it.
According to the manufacturers data the HP achieves a COP of 2.5 at 17 degrees OAD, and 3.7 at 47 degrees OAD with a 70 degree IAD. If the thermostat is turned down (i.e. to 60 degrees) then there's less 'lift' required, the compressor doesn't have to work as hard, and the COP rises from 2.5 to 3.0 at 17 degrees. We turn the thermostat way down when we aren't there (its more of a vacation/weekend home) allowing the ASHP to operate more efficiently.
An ASHP puts out less heat when it gets cold outside, but even at 10 degrees outside its cheaper to operate than the propane furnace. I think if you have a backup heat source already, then an ASHP (mini-split or traditional) is cost effective almost everywhere in the US compared to propane or oil at current prices. At my electric rates ($0.16 / kwh) I figure it costs about half as much over the heating season compared to propane.
A couple other comments:
1) I initially had trouble with my heat pump regularly tripping the high pressure limit switch, and I wasn't getting the $$$ savings I expected. I suspected non-condensables in the system from an insufficient vacuum during install. The tech evacuated and recharged. It was better but I was still getting some trips the next season. I suspected that the system was overcharged (its hard to accurately charge in the winter when my system was done).
2) In the end I decided to take the EPA 608 test and get some tools so that I could work on and maintain my own system. The test wasn't hard and I would recommend it if you want to install or tweak your own system. I recovered some of the charge from my system and was able to fix the pressure tripping problem I had. It brought the high-side pressures down to where I expected and there also seems to have been a noticeable reduction in electric usage. I'm pretty pleased with that.
3) I'm looking to add another small heatpump to a separate part of the house and after reading the "home-made heat pump" thread I'm considering trying to build one. I have the stuff now, but we'll see what comes of that
|04-08-10, 06:11 PM||#5|
Join Date: Feb 2009
Location: Woburn, MA
Thanked 244 Times in 224 Posts
Just looking at today's Diesel $3 to $3.20 locally (which tracks with home heating oil)
and the $0.201 per kWh that I'm paying, I think using the Sanyo is costing about 1/3 the cost of oil heat..
You comment about "regularly tripping the high pressure limit switch" is interesting to me,
since maybe I've had the same kind of problem.
Even with a brand new outdoor unit, my Sanyo 24KHS72 still wants to
draw too much current when given a call for a large temperature change.
If I click up the remote thermostat by 4 or 6 degrees, the system
is likely to slowly increase power use up to 3 to 3.5 kw..
At about 3.5 kw, something gives, and it instantly cycles down to 40 watts..
I'm starting to wonder if my old outdoor unit developed a leak because of over-pressure.?.
I did one short test with the new outdoor system (calling for 80 degrees) and
quickly backed-off when it got up to 3.0 kw..
Right now, we are being very careful to call only for 2 degree (F) increases
and the unit is working fine. We are getting the expected output per kW used.
During normal power peaks (2 degree increase), we see a 2.0 to 2.5 kW peak
which slowly coasts back down to 1.5 to 0.460 kW depending on weather.
We used the AC mode this week, when we had one day of summer, and found
out that the drain hose wasn't crushed during installation..
The heat mode is back on today and intermittently using ~460 watts to keep the house nice and warm..
April is mostly cool here and we are using the Sanyo every day. So far (as of 18:00 April 8) we are up to $2.26..
April is going to be a good month for the e-bill..
|04-09-10, 12:52 AM||#6|
The info that gets put out here is beyond expectations. Thanks!
I have been on the road, sorry for the delay/response to all of ya.
Fred--is the York unit 410a? 410a does run much higher pressures, I would guess there are a lot of 'pro' hvac folks not real savy on the newer stuff. Heck, around here everyone just gets a stupid look on when you talk ashp, mini-split, 410a, etc. Totally lost on 'inverter' technology. Thats real interesting about the EPA cert. also. Got a soft spot for York, we use a lot of their units, although they are 100-1000's of horsepower units. It makes this home stuff hard to get small enough to understand/believe in.
The Dakin vids were great, I did not think to search YouTube-thanks.
Xringer-Your Sanyo info is causing sleeplessness, and obsession. Thanks!!
I am still debating, name brand, sit back and enjoy, or el cheapo and take my chances and/or hack it.
|04-09-10, 10:12 AM||#7|
Join Date: Mar 2010
Thanked 1 Time in 1 Post
The York units are R-22 not 410a. High side pressures should be below 200 psig, assuming there is adequate airflow on the indoor unit. I initially had problems with airflow (the contractor who did the original install undersized the returns), but once that was sorted out the pressures were still way too high (it had to be > 300 psig to trip the limit switch). I finally determined that the subcooling was very high which is consistent with having excess refrigerant flooding the condensor. In effect too much of the condensor is being used to hold liquid refrigerant and not enough is available for heat transfer. The HP compensates by raising the pressure and hence the temperature to get sufficient heat transfer across the reduced condensor surface. I've read that the newer HPs are sensitive to charge level and my experience bore this out. I only had to remove a small amount of charge (into an EPA certified recovery tank) and everything worked right. I could also see the effect on the very next electric bill.
I went w/ the older R22 unit primarily because I was replacing an old R22 AC-only unit and I wanted to reuse the old linesets. R410a is not compatible w/ the mineral oil used in R22 systems, and so most installers recommend you replace the linesets if you upgrade to R410. I didnt' want to have to do that (my linesets were fine and changing can be a messy operation in an existing structure).
Also for the York units I was considering, the R22 model put out slightly more heat than the R410a unit, so I stuck w/ R22. I picked up a 30 lb bottle of R22 from ebay (thats one thing the EPA cert allows you to do) and so I should be good on refrigerant for a long time.
When I was installing the system, I spent some time looking at the type of thermostat I wanted. Most brands have "dual-fuel" capable models that will switch on the backup heat (propane in my case) if the outdoor temp goes below some preset temperature. The York has a builtin demand-defrost controller that has this ability, but what I wanted was some way to run the heat pumps as long as the heat they produced was cheaper than propane -- even if the outdoor temp was below the point where the heat pump could supply sufficient heat to maintain the set temp. The solution I found was to get a fairly simple dual-fuel thermostat that had a 2 stage differential -- the heat pump turns on when the temp is .5 degree below the set point, and the propane turns on when the temp is 2.5 degrees below the set point. This allows the heat pump to run even when it can't keep up with the heat loss from the home. In this case the ASHP will continue to put out heat while the indoor temp slowly drops -- when it gets to 2.5 degrees below the set point, then the propane furnace comes on and cranks the temp back up to the set point and the whole cycle starts over again. That said it has to be very cold out (<20 degrees) before this will occur. At higher temps the heat pump handles the whole load except during defrost cycles.