Bryant ERVBBLHA METHOD TO SIZE ERVs and HRVs, Heating And Cooling Load Charts, Ventilator Sizing

METHOD TO SIZE ERVs and HRVs

Ventilator Sizing

Tables 1 and 2 should be used to determine the required airflow for a home. These guidelines are taken from ASHRAE 62.2-2007.

Table 1 – Ventilation Air Requirements, cfm

FLOOR			BEDROOMS
AREA (ft2)
	0---1	2---3		4---5	6---7	>7
<1500	30	45		60	75	90
1501---3000	45	60		75	90	105
3001---4500	60	75		90	105	120
4501---6000	75	90		105	120	135
6001---7500	90	105		120	135	150
>7500	105	120		135	150	165

Table 2 – Ventilation Air Requirements, L/s

FLOOR			BEDROOMS
AREA (m2)
	0---1	2---3		4---5	6---7	>7
<139	14	21		28	35	42
139.1--- 279	21	28		35	42	50
279.1--- 418	28	35		42	50	57
418.1--- 557	35	42		50	57	64
557.1--- 697	42	50		57	64	71
>697	50	57		64	71	78

/ HRV

HEATING AND COOLING LOAD CHARTS

Although the ventilators process the outside air before it enters the home, additional heating and cooling loads need to be considered.

ERV

HEATING LOAD BTUH

Outside		Heating Load (Btuh) @
		Inside Design Temp 72°F
Temp °F
	ERV1150	ERV1200	HRV1150	HRV1250
–25	5186	8143	6636	10603
–20	4919	7723	6294	10057
–15	5075	7967	5952	9510
–10	4783	7509	5610	8964
–5	4491	7051	5268	8417
0	4200	6594	4925	7871
5	4234	6647	4583	7324
10	3918	6151	4241	6777
15	3958	6214	3899	6231
20	3611	5669	3557	5684
25	3264	5124	3215	5138
30	2916	4579	2873	4591
35	2569	4034	2531	4045
40	2222	3489	2189	3498

The heating load chart shows the heating loads in Btuh for a range of winter design temperatures for each model of ventilator.

EXAMPLE: The heating design temperature for Little Rock, AR is 20_F. The additional heating load of the ERVBBLHA1200 at 20_F is 559 Btuh. This additional load should be taken into consideration when sizing the heating equipment.

COOLING LOAD BTUH

Outside	Cooling Load (Btuh) @ Inside Design Temp
	72°F and 50% Relative Humidity
Enthalpy
Btu/lb	ERV1150	ERV1200	HRV1150	HRV1250
30	380	640	670	1071
31	618	1040	1090	1741
32	855	1441	1509	2411
33	1093	1841	1928	3080
34	1331	2241	2347	3750
35	1568	2641	2766	4419
36	1806	3041	3185	5089
37	2043	3441	3604	5759
38	2281	3842	4023	6428
39	2519	4242	4442	7098
40	2756	4642	4861	7767
41	2994	5042	5280	8437
42	3231	5442	5699	9107

The cooling load chart shows loads in Btuh as well. To use the cooling load chart, first find the design enthalpy from a psychrometric chart using the design dry bulb and wet bulb temperatures. The cooling load can then be found for a range of enthalpies for each ventilator.

EXAMPLE: The design dry bulb temperature for Miami is 90_F and the average wet bulb at that temperature is 77_F. Using the psychrometric chart, the enthalpy is about 40.5 Btu per pound (Btu/lb) of dry air, which would round up to 41 Btu/lb dry air. In the left column, at 41 Btu/lb dry air, the ERVBBLHA1200 has an additional cooling load of 5042 Btuh, while the HRV1150CFM unit has an additional cooling load of 8437 Btuh.

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