The Fans

Looking at the specifications of propitiatory systems it seems that the fans are nothing special. They typically use Axial flow fans with AC voltage motors around 60 Watts seems suitable for our house. In order to allow me to do this without an electrical certificate my system is entirely 12 volt. 

The fans I have are pretty quiet to so it seems like win win to me less that US$30 each for the 60 W devices and US$16 for the boost fans.





Computer fans are a good low cost option. Quiet long lived and they have built in speed controllers too.

I am using two fan types in the system.

Specifications:
-- Size: approx. 120*120*38 mm
-- Voltage: 12(V)
-- Blast Capacity: 280.38CFM
-- Current: 5.0A
-- Rotate Speed: 7500CPM(r/min)
-- Noise Level: 64DBA
-- Wind Pressure: 24.60 mmH2O
-- Bearing: High precision double ball bearing
-- Operating Temperature: -10℃ ~ + 70℃
-- Storage Temperature: -40℃~+70℃
-- Power range: Plus or minus 15% of rated power supply
-- Insulation Resistance: More than 500 megohm
-- Fan Frame: Injection molding, PBT+ 30% glass fiber + VO class flame retardant.
-- Fan Blade: Injection molding, PBT+ 30% glass fiber + VO class flame retardant.
-- Suitable for workstation cooling/server CPU cooling.


Specifications:
Size: approx. 120*120*37 mm
Voltage: 12(V)
Blast Capacity: 267CFM
Current: 1.85A
Rotate Speed: 6500RPM(r/min)
Noise Level: 70.5DBA
Fan Interface board: 4 pin interface
Bearing: High precision double ball bearing

The larger capacity fans are used in the ERV heat exchanger and are the main fans for the system.  The others are lower powered and used as inline boosters or filter fans.

There is an additional 60 Wall fan in the exhaust 2 way Turbo valve to help boost exhaust flow in a purge situation. e.g. curry button




I have some ideas about the fan control algorithm gleaned for the www, basically I expect to be balancing the flow in flow out under any situation. We also want the ability to purge the air volume as quickly as possible (Curry Button)

Speed controllers

The Heat Exchanger

Under construction It took around 6 hours to layer the core Based on a 60 Litre Sistema box with a 400 X 400 X 350 6 mm Coroplast core. The fan speed controller is mounted on the end so it takes a 12V 10 Amp supply from the power system and 2 analogue 0 to 5 V signals for speed demand. The pink foam is a NZ$12 exercise matt which insulates it for both sound and heat quite nicely. 60 Litre Plenum on the vent side See https://greenwayerv.blogspot.com/2020/10/we-added-60-litre-plenum-on-vent-side.html

Home Ventilation Heat Exchanger

The Experiment

First things first an experiment. I had been looking around at various homemade ERV core designs and eventually decided to try a Coroplast design. The experimental core was tiny 12 X 12 X 12 cm using 3 mm Coroplast Nice isn't it :) 20 80 mm PC cooling fans at a fixed speed four temperature probes. Here is the full scale one around 40 X 40 X 35 cm using 6 mm Coroplast A Wemos D1/R2 for instrumentation sending temperatures via MQTT to Node-Red. I'm was not totally convinced by the numbers but it did definitely exchange significant amounts of heat. I checked the calibration and it was good compared to my multi-meter TC probe. In any case it seems to work even at such a small scale. Never did understand why it seems to gain more heat that it lost from the exhaust steam, checked for leaks there were none. Any way a hairdryer experiment showed it worked and heat was transferred too so I was happy that it would probably work at a larger scale.

Heat Exchanger Low Ambient 86% Heat Recovery

Drop on exiting air 2.9C Heating of incoming air 2.5C So 86% of the heat recovered

Added a 60 Litre Plenum air-distribution box on the fresh air side

A bit or research and it seems a plenum on the outlet of the heat exchanger seemed worth a try. 60 Litre Plenum on the vent side. Seems to make the vents more balanced measuring the flow I can regulate the rate more evenly with one vent having less effect on the others, I'm going to add a presure sensor to the chamber see if there is any pressure in it I noticed coupling between room vents. e.g. I set one room and move to the next then recheck the first vent and its flow rate was changed. I was never happy with all those Y junctions, a very poor manifold design I suspect. As an added bonus its made the vent even quieter too. It works well within a range I can set the vent flows independently of one another, also the living room and office flows are much improved which have the longest ducts. The flow at the office and living room are 50% higher if needed now which is great for working at home. The office got warm and sticky in the past, not anymore. More Photos Sound test My refere...

The ERV Data Acquisition System

Progress over the weekend with the ERV DAS The 999's are me testing the sensor disconnected response. I have a Pitot tube left over from an RC plane I think I might put it in the inlet air stream Pin assignment in the Arduino sketch DHT dht[ 4 ] = {DHT( 4 , DHTTYPE),DHT( 0 , DHTTYPE),DHT( 2 , DHTTYPE),DHT( 14 , DHTTYPE)}; There are 4 DHT22's inside heat exchanger lid, shown below. Sensor locations Arduino code #include < Arduino_JSON . h > #include < ESP8266WiFi . h > #include < MQTT . h > #define LED_PIN LED_BUILTIN //LED_BUILTIN is built in LED #include "DHT.h" // Uncomment whatever type you're using! #define DHTTYPE DHT11 // DHT 11 //#define DHTTYPE DHT22 // DHT 22 (AM2302), AM2321 //#define DHTTYPE DHT21 // DHT 21 (AM2301) WiFiClient net ; MQTTClient MQTTclient ; const char ssid [ ] = "Network" ; const char pass [ ] = "DF@#$%" ; // the IP address for the MQTT server char MQTTip [ ...

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