Having the system tested will cost thousands ???
504 West Thomas Moore Way Street, Spokane, WA 99201
phone: (509) 325-2576
Testing = *$,$$$.$$
801 East 2nd Avenue, Spokane, WA 99202
phone: (509) 533-0498
Professional air balancing is a niche market usually reserved for the commercial sector. As a result it is usually pretty expensive for a homeowner to have it done. Alternatively you could hire an NCI certified HVAC contractor. Most of them are not on the same level as a true commercial air balancer. But they are often head and shoulders above a typical residential contractor. Obviously you should give your installing contractor every opportunity to fix the problem before you go to such lengths.
If you're interested in a primer on zoning I wrote this. It focuses on gas heat with air conditioning. But a heat pump is essentially an air conditioner in reverse. So generally speaking the principles still apply. The focus of what's linked is on airflow. And airflow is even more critical for a heat pump than it is a gas heater or straight air conditioner.
The cooling coil of a heat pump in summer becomes the heating coil in winter. You could call it the radiator for the compressor. If you severely reduce airflow you'll cause the compressor to quickly overheat and shut down. With just one zone calling it's extraordinarily unlikely that you're maintaining proper airflow. Even with two out of three zones calling you may have the same problem. If the compressor is shutting down on its safeties then that would explain why it's taking so long to heat up.
Dan you are confused, there is no significant loss in capacity at 40 degrees. There may be a loss but insignificant. The balance point is where the loss of the structure equals the capacity of the machine. This is a fiarly large system and if sized properly he has a 18kw heater (This should be sized for full heat loss). 17.5kw equals 59,727 btuh total load for the coldest of nights.
Any one who works on heat pumps would come to the conclusion that this heat pump will perform well into the low 30's in this home maybe even the high 20's. He doesnt need the 60k of heat until its 0 out. at 30 degrees outside his heat loss may only be 25k. But we dont know what his load calcs said.
If he really wants to know where the problem is, he should open the zone dampers, close any bypass and run the system. If the system performs, then he's got a zoning issue. The implication is that zoning is just as good as multiple units and it isnt, its a lesser expensive way to zone a home.
Originally posted by docholiday
You are confused, there is no significant loss in capacity at 40 degrees. There may be a loss but insignificant.
The balance point is where the loss of the structure equals the capacity of the machine. This is a fiarly large system and if sized properly he has a 18kw heater (This should be sized for full heat loss). 17.5kw equals 59,727 btuh total load for the coldest of nights.
Any one who works on heat pumps would come to the conclusion that this heat pump will perform well into the low 30's in this home maybe even the high 20's.
He doesnt need the (Full ..added) 60k of heat until its 0 out. At 30 degrees outside his heat loss may only be 25k.
But we dont know what his load calcs said.
page 6, 3rd line,
47,000 BTUh at 47'F
29,000 BTUh at 17'F
Additional ARI rating: 35,000 BTUh at 35'F ...
__ 25% reduction (perhaps Significant % to most people for 12'F decrease in Outside temp) in Heat Pump capacity
when Outdoor Temp drops from 47'F to 35'F.
Heat loss is very likely > 35,000 BTUh at ~35'F
(70-35= dT= 35'F = Inside - Outside Temp)
based on my Manual J calc for a typical 2,800 SF house in WA.
Heat Loss for 63'F dT ( 7' F Design Temp for Spokane)
is >_ 60,000 BTUh.
Balance Point should be 36'F +/-
for this 2,800 Sq.Ft. residence,
Rheem RPPB049JAZ/RBHK24J18 4-Ton heat pump and
2,500 foot elevation in Spokane (48' N).
If the heat pump is not running quite At Design conditions, the Balance Point could be a little higher.
Owner may determine the balance point based
on his actual observations in the coming weeks.
[Edited by dan sw fl on 10-09-2005 at 09:59 AM]
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
So you're suggesting we were at (or below) balance point yesterday morning? If this is the case, shouldn't the system have activated the supplemental heat, or is this normal for these units to run non-stop for hours WITHOUT aux heat?
"...with an outside air temp of 34 deg, this system came on at 3AM, and NEVER SHUT OFF until 6:30 and then only for about a min...."
If below the balance point,a typical system will cycle the strip heat on and off,to maintain the indoor temp near the setpoint ,while letting the heat pump run continuously.You can tell if this is the case,by hotter supply air ,when strips are on,followed by cooler,when they are off.
Some mfrs. have better control systems that bring on say 3Kw of strip heat as needed,maintaining a more even supply air temp.,but the heat pump still runs all the time below the balance point