Heat Recovery versus Heating Loads
Heat Recovery versus Heating Loads
(OP)
Hi,
What is your oppinion on the effect of heat recovery (in 100 % fresh AHU), on the Heating Capacity Calculation? Should some or all be considered? Normally I don t use it to low the Heating capacity, but... The only reason i can find against including it as a saving, is during the system star up, once the interior conditions are below the design. Thanks, Regards
What is your oppinion on the effect of heat recovery (in 100 % fresh AHU), on the Heating Capacity Calculation? Should some or all be considered? Normally I don t use it to low the Heating capacity, but... The only reason i can find against including it as a saving, is during the system star up, once the interior conditions are below the design. Thanks, Regards





RE: Heat Recovery versus Heating Loads
RE: Heat Recovery versus Heating Loads
Although the current energy codes in these parts requires you to size the unit with energy recovery included. (downsized), which I do for cooling, but use the above frost excuse as reason to not take the credit on the heating side.
knowledge is power
RE: Heat Recovery versus Heating Loads
1 - System start up in the deisgn day;
2 - Building is onocupied and with no other internal gains;
It depends on the type of buiding but the odds are pretty low...
RE: Heat Recovery versus Heating Loads
for the system start up, I belive it is better to intreduce an amount of fresh air with let say 3C into the coil than intreducing the same amount of the fresh air with 0C directly to a unit coil.
in your case I guess that each 1m3/hr(or 0.58cfm) of the fresh air needs about 7Kcal/hr(28 Btu/hr)then you can know how much energy you need for your fresh air and how much the recovery could give you, compare with recovery unit cost then deside.
Do not forget about cooling too. your are using electricity for cooling.
RE: Heat Recovery versus Heating Loads
I would not include the heat recovery, like mentioned before, if the recovery goes down, what would happen? Size the coil for the full 100%OA from 0 to whatever your lat is.
RE: Heat Recovery versus Heating Loads
I agree that we should not consider heat recovery in calculation but let us think about it shortly
heat recovery unit usually raise the OA temp from 0F to about 40F in my knowledge(also we could find for 0C)
if we need to keep 70F forexample then without HRV we need
Q1= K.(70-0)=70K, but with HRV
Q2= K.(70-40)=30K, which k is a constant related to cfm and is the same in both cases, we see that Q1 is much mor than Q2.
if the recovery goes down no disaster would happen because it is a part of the system, simply we call maintanance team and fix the problem, what if the RTU or the furnace itself goes down?
RE: Heat Recovery versus Heating Loads
RE: Heat Recovery versus Heating Loads