“You want to check the pressure difference between the two sides of the filter...so, one hose would need to go on one side, and the other on the other. I suppose you could leave one side open, and compare the difference when measuring both sides of the filter with the other hose as well.”
Since the filters are located in the returns, one side of the filter(s) is just the house, so an open port on the manometer would be reading that. Yes?
“Would your Idea work?, of course it will, Is it necessary ?, No.”
It seems to me that it is necessary if I want to maximize filter life, and @ $80 per change I definitely want to. I do think you could make an argument as to whether $80 worth of filters is necessary. We are trying to reduce dust but I admit there is much I do not know and/or understand about this field.
“You want to be careful with Merv filters especially if you are running A/C The added restriction can often cause the evaporator coil to ice up.”
Point taken but; I have a 1,000sf house with a 3 ton unit and 4, (count them – 4!) 20x20 returns, due to misguided efforts of the first HVAC guy I hired. The second guy thought that since the filters/returns were already there it would not hurt anything to leave them there. Since this gives me over 11sf of 4” filter area my thinking is that I can pretty much ignore restriction concerns. Do you guys agree?
“One side of the manometer needs to be open to the atmosphere. If there are multiple check points he either needs multiple manometers or to take readings at each location.”
My thought was that if I took a reading from the plenum I would get a “collective” restriction reading. If I were to do what is probably the correct way, and measure each filter, I would still be faced with the problem of putting one fresh filter in a system with three partially clogged filters. Air is going to be drawn through the filter(s) with the least amount of restriction. As the filter becomes clogged the air will begin to be drawn more through the next least clogged filter and so on.
Personally, I think they are a waste of money. There are other and much less restrictive methods for removing particulate and bacteriologic as well as virus bugs, and while the initial cost is more, they will save money in a very short time.
I am very interested in these methods. Would you elaborate?
A Note: I hope I am not coming off as argumentative or picky. My only objective is one of understanding and I thank you all for your patience, not to mention your expertise.