Adding Secondary Heat Recovery Core to HRV?

Andrew Murphy · 09-19-18, 07:28 PM

Hi,
We have a Venmar Evo 5 700 HRV HEPA that was installed in August of 2017. I and another family member have severe lung issues in which we have to just about run the HRV in Turbo mode for extended time periods or continuously (I am fully aware that it is not good for the motor). We physically couldn’t run the air exchanger as much as we needed to last winter because the house just got way to cold. After doing some Google searches I was wondering if I could add a second core to the HRV something similar to a post on this site about someone building an HRV with 2 cores but more like an inline accessory like a HRV filter box. My father said it might reduce efficiency or increase it depending on weather conditions. I have it planned and everything (Even got the chloroplast!) but was wondering what everyone at Eco-renovator thought about it. We are trying to reduce heating costs.

jeff5may · 09-29-18, 03:21 AM

All depends on details. If the time and attention to detail is invested in building the unit, it will operate the best that it can. If the unit is oversized, there will be less drag and better heat transfer than a smaller one and less friction at the same flow rates. Doing it right the first time is always a good objective, but you have to start somewhere. The first one is usually the worst one if you know what I mean.

u3b3rg33k · 09-30-18, 01:32 AM

you may want to re-visit your needs.

HEPA filtration is one "need". typically used in hospitals when they do 100% outside air.
outside air requirement - how much fresh air does your building need?
heat/cooling for your house
humidification (for winter)

these are not all one and the same.

if someone in your house has problems breathing unless you run the HRV continuously, you need to figure out why, and address that issue.

too much CO2? too much off-gassing of some material? those are issues addressed by an HRV.

keeping dust down is is another, and a hepa filter is often a band-aid. air infiltration/dust source (pets? woodshop in the basement?) should be considered.

the cooling/dehumidification impact should be factored in to your operating vs first cost for the HRV/ERV choice. I don't really see a problem with running the HRV motor at full power. you may want a more efficient one, and if you're up north, why an HRV not an ERV?

09-19-18, 07:28 PM	#1
Andrew Murphy Lurking Renovator Join Date: Sep 2018 Location: NLFD, Canada Posts: 3 Thanks: 0 Thanked 0 Times in 0 Posts	Adding Secondary Heat Recovery Core to HRV? Hi, We have a Venmar Evo 5 700 HRV HEPA that was installed in August of 2017. I and another family member have severe lung issues in which we have to just about run the HRV in Turbo mode for extended time periods or continuously (I am fully aware that it is not good for the motor). We physically couldn’t run the air exchanger as much as we needed to last winter because the house just got way to cold. After doing some Google searches I was wondering if I could add a second core to the HRV something similar to a post on this site about someone building an HRV with 2 cores but more like an inline accessory like a HRV filter box. My father said it might reduce efficiency or increase it depending on weather conditions. I have it planned and everything (Even got the chloroplast!) but was wondering what everyone at Eco-renovator thought about it. We are trying to reduce heating costs.

09-29-18, 03:21 AM	#2
jeff5may Supreme EcoRenovator Join Date: Jan 2010 Location: elizabethtown, ky, USA Posts: 2,431 Thanks: 431 Thanked 619 Times in 517 Posts	All depends on details. If the time and attention to detail is invested in building the unit, it will operate the best that it can. If the unit is oversized, there will be less drag and better heat transfer than a smaller one and less friction at the same flow rates. Doing it right the first time is always a good objective, but you have to start somewhere. The first one is usually the worst one if you know what I mean.

09-30-18, 01:32 AM	#3
u3b3rg33k Apprentice EcoRenovator Join Date: Mar 2018 Location: Rustbelt, USA Posts: 114 Thanks: 5 Thanked 10 Times in 9 Posts	you may want to re-visit your needs. HEPA filtration is one "need". typically used in hospitals when they do 100% outside air. outside air requirement - how much fresh air does your building need? heat/cooling for your house humidification (for winter) these are not all one and the same. if someone in your house has problems breathing unless you run the HRV continuously, you need to figure out why, and address that issue. too much CO2? too much off-gassing of some material? those are issues addressed by an HRV. keeping dust down is is another, and a hepa filter is often a band-aid. air infiltration/dust source (pets? woodshop in the basement?) should be considered. the cooling/dehumidification impact should be factored in to your operating vs first cost for the HRV/ERV choice. I don't really see a problem with running the HRV motor at full power. you may want a more efficient one, and if you're up north, why an HRV not an ERV?