[Bill7]

What should I look for in one? There seems to be plenty of options. Not sure I need the $350, ut wondering if the $100 will work.

Background:

I have a Venmar air exchange in the house. All electric heat, so not heating/cooling involved. The fresh air duct keeps freezing in the winter (usually with sub-0 temps). HVAC Co. has re-balanced the system twice. They also re-ran the intake (snow was coming in??), but it still froze up. It still ran, because the moisture in the duct didn't completely cover everything. The problem is that when warmer temps come around, I get water drips from the unit and from the fresh air duct. They have come out twice since installation (3 time total) and I am still experiencing problems (well, not now, 'cause it is summer). I asked the tech on the last visit, and he said "it wasn't as bad as some."

I am planning on adding a vent to the system, and I am thinking that I can balance the system myself.

Is this a balance issue?

Thanks

 

[HVACDave]

Don't quite understand your freezing issue. Are you not using insulated flex ducting? If you are then as long as you have the ends sealed up well against the unit and your outdoor hood, there should be no ice accumulations as the moisture in the indoor air shouldn"t come into contact with the cold.
You can use a digital manometer to balance your system, you can use a flow collar if you want easy access for measurement in the future. Do you have balancing dampers built into the unit, or are they external in the ductwork. Do you still have the installation instructions? it should detail balancing procedures and recommended methods there. I believe some of the Venmar units have ports right in the front cover for measuring pressures, does yours have this feature?

 

[Bill7]

Thanks fr the reply. Sorry I couldn't explain things better.

1. Yes, there is insulated flex ducts going from the outside to the unit.
2. The ice is accumulating inside this insulated duct just prior to the unit.
3. This unit does have the holes for the probes, and I do have the instructions somewhere, but no manometer.
4. There are dampers built into the unit.

More than anything, I am wondering if some of this buildup is normal, considering the temps we get here.

I am planning on replacing the duct, as I had to poke a hole in it to get it to drain. Possibly adding a vent. That's where having a manometer would come in handy, as I could do the vent myself. I would feel bad doing all the work, then paying a service fee just to balance the system.

Thanks for the reply.

 

[HVACDave]

I've installed quite a few HRV's in Manitoba (so similar climate to you or worse in winter), but haven't found the issues you are facing. It sounds as if warm moist air is travelling back into the fresh air duct in the off cycle and condensing then freezing there. A couple of questions:

1. Is your unit installed where it ties into the furnace ductwork? If so, is the unit interlocked with your furnace fan so that whenever the unit runs the furnace fan also runs?

2.Is the ducting that brings fresh air to the house tied into the discharge side of the furnace ducting or the return air side of the furnace?

There are a couple of different methods used for installation, so I am just trying to figure out how yours is installed.

 

[Bill7]

No furnace connection at all. We have all electric baseboard or in-floor heat.

I guess what I am thinking is that the incoming air is some how being restricted as it reaches the unit. So, I guess this would be a balance issue.

I am planning on cleaning the filters this weekend (windows all open, unit off). I will take a picture and see if I can upload to a post.

Thanks

 

[yuri]

Sounds like they are not balancing it properly. You need a very low measuring gauge called a magnehelic gauge to measure ACCURATELY the very small draft that a HRV uses. Most manometers cannot go that low unless you special order one for that purpose. Magnehelics are used for very fine measurement of airflow in commercial equipment ductwork and for differential pressure measurement of filter banks etc. Sounds like their attitude is bad also. Post a bunch of pics of the pipes coming into and out of the unit and how they enter and exit the house also. Post the complete model and series number of the unit. Your defrost thermostat may be inaccurate or the defrost damper motor not opening properly as well as a bunch of other scenarios. Not my favorite unit, I prefer Lifebreath, no plastic parts in them and their damper motor is direct coupled. Go to their website and search it and phone their 1-800 # as there was a factory recall. safety issue with some units and motors overheating and starting on fire. They have a safety circuit breaker plug to deal with that which they send you.