I have a new York Affinity 13 Seer YZB, 3.5 ton. It is rated at 42,000 BTU by the manufacturer. I am not sure that I am getting this. At this moment the outside temperature is 22F. With the heat pump working I am getting a 6 degree rise at the registers, compared to the room. For example, right now I have a thermometer showing a room temperature of 67F. When I place the same thermometer over a heating duct that is located directly above the heat exchanger, it shows a temperature of 73F. This makes me think that the heat pump is not working to spec because I have a dual stage 40,000 / 80,000 two stage gas furnace. After running for 15 minutes or so at the current outside temperature, the system switches to gas heat because the heat pump has not done the job in an acceptable period. The furnace starts at 40,000 BTU and hardly ever jumps to 80,000 because after 5 minutes or so the desired temperature is reached. At 40,000 BTU the air coming from the register is 80F. When the 80,000 switches in, the temperature at the register is about 120F.
Shouldn't the heat pump, if it is really producing 42K BTU be increasing the heat at the register to at least the 80F of the gas furnace? Or, is the 42K BTU a rating that applies only to a higher outside temperature? I have searched the York internet sites and many others and I can find nothing to indicate what should be happening. I do not believe that my dealer is able to answer such questions because he has been evading me. Still, I think that my questions are reasonable after spending so much for the new system.
it is a good question.
Originally posted by mpagnan
, is the 42K BTU a rating that applies only to a higher outside temperature?
I think the answer is yes.The rating is based on a specific temperture,47 degrees or something.
[Edited by jacob perkins on 12-16-2005 at 09:42 PM]
your heat pump may be rated at 42k at 40 deg, but certaintly less at 17 deg.
the balance point of your home would be when your heat pump is running continuously and maintaining your desired thermostat setpoint without starting the furnace.
it sounds as if the heat pump lockout temp is set to low, it needs to be raised.
good luck and Merry Christmas!
in general, the output of a heat pump at 17F is roughly 2/3rds of what it is at 47F. So if the 42,000 btu rating is at 47F (sounds about right for a 3.5 ton unit), it will be about 28,000 btus at 17F.
But that temp rise sucks, even at a register. I would retest the DeltaT as close to the heat pump as possible and see what you get. At 22F outside it should be roughly around 15F rise.
Also, you may want to check the amount of air you are moving. Even still, your system sounds a little deficient.
Has anyone checked the charge in it? May want to call a pro on this one.
I suspect it needs to be checked. Not so much a capacity concern but duct losses. You cannot look at the temp at the register without reading the actual plenum temperature and make any kind of diagnosis. There could be serious duct leakage or losses (I agree it sounds low). The actual airflow has not been checked (may be too high). The line set hasnt been disclosed regarding size, length, or vertical seperation (100' of lineset will certainly have significant losses in heat mode). Was the OD coil frosted at the time the reading was made or just coming out of defrost? Whats the actual balance point?
If you are concerend, call the company that installed it. They should be able to address it.
You didn't give the furnace model, or the indoor coil model, along with the other info Doc mentioned.
I would have the the duct work checked also besides the charge.
Your heat pump has about a 28,000 btu rating at 22° outdoor temp, and 80°indoor temp, your furnace at 40,000 input is only blowing out 7° warmer air.
Sounds like a duct problem/air flow.
List all model numbers, and we can tell you more about your systems performance.
Heat Pump Performance Expectations
YORK 13 SEER 3.5 ton YZB heat pump has
Originally posted by beenthere
Sounds like a duct problem/air flow.
List all model numbers, and
we can tell you more about your systems performance.
~27,000 btu rating at 17° Outdoor Temp
.................... Coefficient of Performance
47° F 44,000 BTUh .. 3.7
35° F 33,000 BTUh .. 2.9
17° F 27,000 BTUh .. 2.5 ( edited)
_____ Q= CFM * dT * 1.08
_____ dt = Q / (CFM * 1.08)
CFM _ = 1400 CFM for a 3.5 Ton
Q 27,000 BTUh at 17'F
Temperature at the furnace outlet should be
17'F higher than the room temperature
when running only the heat pump
at outside temperature in the low 20°F s.
If you wish to investigate more specific balance pointS applicable to YOUR house to minimize use of gas furnace,
you must describe house characteristics in some detail
(sq. ft., age, 1 or 2 story, windows: U-value .. area, wall/ ceiling insulation, ... )
and AUX Heat capacity ( perhaps 10 or more kW ?).
Aux Heat + Heat Pump
34,000 + 27,000+ = > 60,000 BTUh in the low 20°F s
Location: _____ Ottawa, Canada
[Edited by dan sw fl on 12-17-2005 at 08:50 PM]
It's Not Rocket Science, But It is SCIENCE
with "Some Art". ___ ___ K EEP I T S IMPLE & S INCERE
Define the Building Envelope and Perform a Detailed Load Calc: It's ALL About Windows and Make-up Air Requirements. Know Your Equipment Capabilities
Dan, I think you got your COP,s backwards.
Which coil match are you using.
This site is amazing. One day after and I get 10 well-informed replies. Thanks to everyone for this imput.
Here are some further observations and answers to the questions:
1) The exact model number of the heat pump is yzb04211. Which is the 3.5 ton 13 seer York "Affinity".
2) The furnace is York "Affinity" model pv9c16p080up11 with varible speed fan and dual stage 40 / 80 BTU option.
3) The air cleaner is a ToxBox electrostatic.
4) Today with an outside temperature of 30F the air temperature at the register was 79F. With these temperatures the heat pump provided all necessary heating. I was surprised that there would be so much of a difference from an outside temperature of 22F the other day and today.
5) The furnace duct on the output side is 20"x20" which splits into one of 21"x8" and one of 15"x8". The duct on the intake side is 21"x8" at the furnace which opens up to 25"x20" to accomodate the air filter and then splits into 2 ducts of 15"x8".
6) The ducts are extremely well sealed with tape and silicon. So, if there are any leaks, they are not in the basement but inside the walls, but I have no evidence of that. All of the ducts in the walls are galvanized 4" diameter pipes passing between the studs.
7) The house has 2185 sq ft but it is well insultated - with r20 in the walls and r56 in the ceiling. The basement is also insultated with r13 walls.
8) One other thing, the thermostat / humidistat is and Aube / Honeywell model th146-n-de. This unit controls the furnace and the heatpump to a degree - in that it switches from heat pump to furnace when electric rates are high.
I believe that I may be on to something but I am not sure. I noticed that today the heat pump would defrost on its own every now and then. However, the other day at the colder temperature, the heat pump did not defroast when the furnace came on. So, when the heat pump started later, the coils were covered in ice. I was wonder why it was not defrosting every time the furnace came on - so that it would be able to deliver its maximum heat potential on start up - that is if the coils were ice-free. Is the problem thus a defrost control problem? Of course, I am just guessing.
I think you said it in that last part-your measurements are based on whether a good defrost has occurred or not.
I have never heard of a thermostat output based on reading the gas and electric bills.Neat-o!
Once your furnace turns on the HP cannot run in heat or defrost mode. It will have to wait until the next HP cycle.
Basically what Doc said.
You should have them your installer come out and check the charge, And Blower CFM in heatpump mode, and the manifold pressures in both first, and second stage heat, along with blower CFM for both stages.
Your return duct is alittle small.
At that temp, your heat pump is pretty much worthless anyway.