Bard 920-0074 qwserv manual Energy Recovery Ventilator Maintenance, Generalinformation, Frequency

TABLE 3

WINTER HEATING PERFORMANCE — (INDOOR DESIGN CONDITIONS 70°F DB)

	Ambient
	O.D.				VENTILATION RATE
	DB	450 CFM 80% Eff.			375 CFM 81% Eff.			300 CFM 82% Eff.
	Degrees F	VLT	HRS	VLS	VLT	HRS	VLS	VLT	HRS	VLS
	65	2430	1944	486	2025	1640	385	1620	1328	292
	60	4860	3888	972	4050	3280	770	3240	2656	583
	55	7290	5832	1458	6075	4920	1154	4860	3985	875
	50	9720	7776	1944	8100	6561	1539	6480	5313	1166
											NOTE: Sensible
	45	12150	9720	2430	10125	8201	1924	8100	6642	1458
											performance only
	40	14580	11664	2916	12150	9841	2309	9720	7970	1750
											is shown for
	35	17010	13608	3402	14175	11481	2693	11340	9298	2041	winter application.
	30	19440	15552	3888	16200	13122	3078	12960	10627	2333
	25	21870	17496	4374	18225	14762	3463	14580	11955	2624
	20	24300	19440	4860	20250	16402	3848	16200	13284	2916
	15	26730	21384	5346	22275	18042	4232	17820	14612	3208
	10	29160	23328	5832	24300	19683	4617	19440	15941	3499
	5	31590	25272	6318	26325	21323	5002	21060	17269	3791
	0	34020	27216	6804	28350	22964	5387	22680	18598	4082
	-5	36450	29160	7290	30375	24604	5771	24300	19926	4374
	-10	38880	31104	7776	32400	26244	6156	25920	21254	4666
LEGEND
VLT = Ventilation Load – Total				HRS = Heat Recovery – Sensible					VLS = Ventilation Load – Sensible

ENERGY RECOVERY VENTILATOR MAINTENANCE

GENERALINFORMATION

The ability to clean exposed surfaces within air moving systems is an important design consideration for the maintenance of system performance and air quality. The need for periodic cleaning will be a function of operating schedule, climate, and contaminants in the indoor air being exhausted and in the outdoor air being supplied to the building. All components exposed to the airstream, including energy recovery wheels, may require cleaning in most applications.

Rotary counterflow heat exchangers (heat wheels) with laminar airflow are “self-cleaning” with respect to dry particles. Smaller particles pass through; larger particles land on the surface and are blow clear as the flow direction is reversed. For this reason the primary need for cleaning is to remove films of oil based aerosols that have condensed on energy transfer surfaces. Buildup of material over time may eventually reduce airflow. Most importantly, in the case of desiccant coated (enthalpy) wheels, such films can close off micron sized pores at the surface of the desiccant material, reducing the efficiency with which the desiccant can adsorb and desorb moisture.

FREQUENCY

In a reasonably clean indoor environment such as a school, office building, or home, experience shows that reductions of airflow or loss of sensible (temperature) effectiveness may not occur for ten or more years. However, experience also shows that measurable changes in latent energy (water vapor) transfer can occur in shorter periods of time in commercial, institutional and residential applications experiencing moderate occupant smoking or with cooking facilities. In applications experiencing unusually high levels of occupant smoking, such as smoking lounges, nightclubs, bars and restaurants, washing of energy transfer surfaces, as frequently as every six months, may be necessary to maintain latent transfer efficiency. Similar washing cycles may also be appropriate for industrial applications involving the ventilation of high levels of smoke or oil based aerosols such as those found in welding or machining operations, for example. In these applications, latent efficiency losses of as much as 40% or more may develop over a period of one to three years.

Manual	2100-533A
Page	6 of 12