Titus Timeout Podcast - How ERVs Work

This week's podcast discusses the basic operation of an ERV.

[@joeyandaya9420]

Question: The Air From inside is same the you exhausted and vice versa?

[@Aznd007]

Can you Explain about TFA units that we are used in HVAC system. when we need to use? instead of this TFA why dont we use normal fresh air fan? is accpectable ? pls explain me

[@rbnjr]

Where i live heat and humidity are kept outside with a large HVAC system, i only want to infuse some fresh air into it. A ERV seems overly complicated and expensive. there is a way to keep the heat outside and bring in fresh air. It has to do with where the fresh air is being drawn in. I am trying to design a system that is much simpler and still provides exactly what i want.

[@TitusHVAC]

As I understand, your existing HVAC system purely cools/heats and recirculates indoor air. As such you have no real need for an ERV. If that is the case, you could simply introduce fresh (outside) air without tempering it, but doing so we increase the cooling/dehumidifying and heating loads your existing HVAC system has to handle. If you are comfortable that it is capable of handling the increased loads that is one option. However, you might you will also need to exhaust a similar volume of the room air as that outside air you brought in. You might consider adding a plate type heat exchanger serving the outside and exhaust air streams to minimize the effects on your existing HVAC system.

[@TitusHVAC]

The enthalpy wheel can be thought of a sponge, the water molecules present in the outdoor air stream are absorbed by the desiccant material in the wheel, then the relatively drier return air from the building is passed through the wheel and absorbs the water molecules into the exhaust airstream. This process only occurs because the relative humidity of the return air is lower than that of the outdoor air, therefore has more capability to absorb water. The direction of the airstream is irrelevant for the moisture exchange process to occur

[@allanfernando5358]

is there chance for both air getting mixed up if yes how many %

[@TitusHVAC]

Cross-flow leakage can occur when the exhaust air leaks from the exhaust side into the supply side through the energy recovery wheel seals or gaps in construction. Generally this is only an issue for critical applications such as lab ventilation. Quality air handling units should have a leakage of no more than around 1% of the design volume at operating pressure. There is a wealth of information available online - search “Energy Recovery Wheels, Crossflow Leakage” for more in depth info.

[@faridehlotfi5603]

In the winter, why the temperature of the return air is more than the temperature of the supply air?

[@mitchb2207]

They are assuming there is a heating coil further down in the system to heat that 60 Degree air up to 70 or so or whatever degree temperature you need to heat your space to.

[@thetraveller__]

Hi, can you please explain Energy recovery wheel with Purge section?

[@TitusHVAC]

The purge section is designed to minimize the amount of air carried over from the exhaust to the supply side of a rotating enthalpy wheel. As the wheel rotates, some return/exhaust air is trapped within the pleated flutes of the wheel. Enthalpy wheels are designed such that the pressure on their supply (outdoor air) side is greater than that on the return (exhaust air) side. The purge section utilizes a fraction of the higher pressure intake air to essentially “blow” the trapped air back into the urn/exhaust air stream and prevent its contamination of the outdoor air stream. Any amount of air used for purging reduces the efficiency of the wheel so it should be limited to what is required by the application. Or a good explanation of the purge section, please see the following www.dac-hvac.com/energy-recovery-wheel-purge-section.

[@thetraveller__]

@@TitusHVAC thank you....

[@adicbn]

Long story short.. you lose heat in the winter and lose cold air in the summer with an ERV system, the only thing you gain is fresh air, also your electricity bills will be higher What's wrong with opening the window to refresh your home instead of having the ERV system? 🤔

[@TitusHVAC]

The principal of the ERV is that you recovery heat and moisture during the winter and use it to pretreat the outside air before conditioning it and sending it to the space. During summertime, you use the return air stream as a heat and moisture sink, removing sensible heat and moisture from the outside air before conditioning it and sending it onto the space. Everything is driven by the sensible heat and moisture differentials between the incoming (outdoor) and exhausted (return) air. The energy and moisture flow is in the direction form the higher value source to the lower value source, thus in winter time heat and moisture is recovered from the return air and transferred to the colder/drier outside air. In summertime the process is reversed and heat and moisture from the outside air is transferred to the air to be exhausted. Opening windows simply results in adding to the space heating or cooling requirement if you intend to maintain a set temperature in the space.