Any benefit to adding 5-inch media filter when new system is installed?

[Florida Joy]

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No offense, but you're not an asterisked pro member, so please stop responding to my posts.... leave it to the pro's, please!

BTW, refrigerant pressures/temps were checked and double-checked by the tech when he repaired leaks and replaced the accumulator two months ago. Since then, except for the reset issue related to filter change, the system has been cooling better than ever.

[Florida Joy]

This is the Ask Our Pro's forum, and only Pro members that have been vetted by the AOPC may post advise here. Please apply to the AOPC today, thank you.

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You may be funny, to some, but you're not helping me at all.

No offense, but you're not an asterisked pro member, so please stop responding to my posts.... leave it to the pro's, please!

[Workin4TheMan]

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[beenthere]

Workin4TheMan, this is the Ask Our Pro's forum, and only Pro members that have been vetted by the AOPC may post advise here. Please apply to the AOPC today, thank you.

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[RoBoTeq]

Could be bad txv, trash in the metering device, partially blocked filter drier, bad pressure switch, gremlins or ghosts in the machine. It needs to be thoroughly checked or more damage may be being done.

[jtrammel]

The air filter shouldn't have anything to do with a high head preasure trip unless the unit is in heat mode. In ac it could be dirty condenser coil, weak or stopping condenser fan motor, overcharged with refrigerant, or a restriction in the refrigeration circuit. It's odd that it seems directly correlated with a filter change.

[Florida Joy]

The air filter shouldn't have anything to do with a high head preasure trip unless the unit is in heat mode. In ac it could be dirty condenser coil, weak or stopping condenser fan motor, overcharged with refrigerant, or a restriction in the refrigeration circuit. It's odd that it seems directly correlated with a filter change.

Odd, indeed. The condenser fan is running strong, with lots of hot air exhaust. I put my hand on the compressor housing and it's not hot. BTW, it was hot when the switch tripped after the filter change, both with the Honeywell MERV 10 and the MERV 11. The coil fins are quite corroded, but no dirtier than usual. I'm afraid if I try to run a hose through the coil the fins will fall off. Yes, I do know the coil has to be rinsed from the inside out.

[Florida Joy]

a 1" MERV 11 could probably ' trip me out' from 200 miles away.

Not sure of the specific impact from a 4" MERV 10.
I would Not use more than a MERV 8 in any case.

If I had health issues, I'd get a portable HEPA unit, that way both me and my equipment can survive.

I'll stick with the MERV 8 for the time being. No real health issues, but too much dust, pollen, etc. does make me sneeze and aggravates my post nasal drip (side effect from blood pressure meds). So far, haven't had that problem inside my house.

But I'd like to know what 3-ton equipment you have in your home that gets you a high bill of $130? Your house is close to mine in square footage (~1800). I'm home alone most of the time and don't use many appliances, but my high bill in mid-August is $250, at about 74 kWh/day. My low bills in mid-December and mid-February are $60 each, at about 19 kWh/day.

My high bill in VA every year, over the 7 years I lived there, was $130 in a 2200 sf 3-story townhouse. I sure would like to see bills like that again!

[udarrell]

The air filter shouldn't have anything to do with a high head pressure trip unless the unit is in heat mode.

In ac it could be dirty condenser coil, weak or stopping condenser fan motor, overcharged with refrigerant, or a restriction in the refrigeration circuit. It's odd that it seems directly correlated with a filter change.

Since you're running it in the cooling mode; jtrammel is on target, except for some restriction exceptions which though usually high, depending on where located, some locations cause the system to pump down.

Maybe it is getting attic air leaked into the return air; then a clean filter would allow an increased evaporator airflow heat-load to possibly trip the head pressure shut-down; it's even more apt to happen, due to hot moisture loaded attic air, if the system is overcharged or has a lot of non-condensibles in the refrigerant system.

[RoBoTeq]

Odd, indeed. The condenser fan is running strong, with lots of hot air exhaust. I put my hand on the compressor housing and it's not hot. BTW, it was hot when the switch tripped after the filter change, both with the Honeywell MERV 10 and the MERV 11. The coil fins are quite corroded, but no dirtier than usual. I'm afraid if I try to run a hose through the coil the fins will fall off. Yes, I do know the coil has to be rinsed from the inside out.

I think you found your problem. If the aluminum fins are eroded, the outdoor coil is not removing enough heat and the head pressure is going up. The only way to be certain is to have the system professionally tested.

[54regcab]

I'll stick with the MERV 8 for the time being. No real health issues, but too much dust, pollen, etc. does make me sneeze and aggravates my post nasal drip (side effect from blood pressure meds). So far, haven't had that problem inside my house.

But I'd like to know what 3-ton equipment you have in your home that gets you a high bill of $130? Your house is close to mine in square footage (~1800). I'm home alone most of the time and don't use many appliances, but my high bill in mid-August is $250, at about 74 kWh/day. My low bills in mid-December and mid-February are $60 each, at about 19 kWh/day.

My high bill in VA every year, over the 7 years I lived there, was $130 in a 2200 sf 3-story townhouse. I sure would like to see bills like that again!

If the bill is only $130 on a 3 ton unit either the person has low electric rates or an oversized AC unit. Figure 12+ hrs per day run time in a peak month for a properly sized unit at a 3,000Watt draw. The AC alone would use 1080KWH per month if sized to run 12hrs per day in a peak month. At 10 cents per KWH that's $108 for AC alone. This doesn't include any other use in the house or the base meter charges/taxes/fees.

[Florida Joy]

Maybe it is getting attic air leaked into the return air; then a clean filter would allow an increased evaporator airflow heat-load to possibly trip the head pressure shut-down; it's even more apt to happen, due to hot moisture loaded attic air, if the system is overcharged or has a lot of non-condensibles in the refrigerant system.

If it's true that "increased evaporator airflow heat-load" from hot, moist attic air could trip the switch, you may be onto something!

Although I had the duct leaks identified and sealed, including my one return directly through the wall under the ahu stand, one contractor who later did a Manual J and further leak testing (in preparation for his new equipment quote) determined there is still a 17CFM leak at the return that needs to be sealed. This space under the ahu is "unfinished", that is, the wall studs below the top of the stand are not covered by drywall. The contractor who sealed the duct leaks attempted to "seal" the space with ductboard, but apparently his efforts were not 100% effective. I would guess the 17CFM of leakage would allow attic air to leak into the return.

With a less restrictive MERV 8 filter, the suction from the return would pull more air in from the conditioned space in the hallway where the return filter grill is. With a more restrictive MERV 10 (Honeywell 4") or MERV 11 (1" pleated) filter, suction from the hallway would be restricted and more air would be pulled in through the "leak" from the hot attic.

Given the poor, but constant, condition of the condenser coil, this added heat load might just be enough to trip the high pressure switch.

Does that make sense?

[Florida Joy]

If the bill is only $130 on a 3 ton unit either the person has low electric rates or an oversized AC unit. Figure 12+ hrs per day run time in a peak month for a properly sized unit at a 3,000Watt draw. The AC alone would use 1080KWH per month if sized to run 12hrs per day in a peak month. At 10 cents per KWH that's $108 for AC alone. This doesn't include any other use in the house or the base meter charges/taxes/fees.

Dan has the same rates as I do through FPL, pretty close to the same weather conditions, and about the same size house. I believe I have a higher heat load from 6 sets of sliding glass doors and an open beam ceiling, but I also have an old, decrepit 3.5 Ton Rheem and a $250 electric bill in August. Everyone keeps telling me 3.5 Ton is oversized and I'd have a lower bill if I'd downsize to a 3 Ton. I'm seriously considering taking the plunge to a 3 Ton and I'd like to know what system Dan has that gives him a high bill of only $130.

[Florida Joy]

Everyone keeps telling me 3.5 Ton is oversized and I'd have a lower bill if I'd downsize to a 3 Ton. I'm seriously considering taking the plunge to a 3 Ton and I'd like to know what system Dan has that gives him a high bill of only $130.

Another comparison I'm considering is my neighbor's house to the NW. Same basic house, exact same layout with a screened room in the back corner that's been enclosed and converted to conditioned space, just like mine. Only three major differences... (1) instead of 3 sliding glass doors that open directly onto the yard on the NE side, they have french doors that open to a covered and screened porch along the back of the house that provides morning shade, (2) they recently installed solar panels on the roof to power the hot water heater, and (3) they have a 3-ton Comfortmaker heat pump that's about as old as my 3.5-ton Rheem. It's also about as corroded as mine, but at least it's still upright because it's on a full concrete slab. Oh, there is one more important difference... they both work every day... and judging from the compressor runtime during the day, they must be turning the tstat up quite a bit when they're not home.

I haven't asked what their electric bills are running, but judging from the current reading on their meter, each of their last 4 bills have averaged $95 less than mine. The meters on my street were changed out for Smart Meters, one by one, all on the same day this past June, so my guestimate of their bills is based on the current difference in our two meter readings, representing almost exactly 4 months worth of usage.

I'd love to save $100 a month or so during the hottest 5 or 6 months of the year!

[54regcab]

The 3 ton would be more apt to loose a little ground during the hottest afternoons, but would catch up when the sun went down. It would lead to a long run cycle which is optimum for high efficiency/low power bills. As we discussed before it's doubtful your 3.5ton unit is actually delivering 3.5tons, most AC units do NOT deliver their rated capacity. 75% of rated capacity isn't untypical, especially on the larger units.

[Florida Joy]

If the bill is only $130 on a 3 ton unit either the person has low electric rates or an oversized AC unit. Figure 12+ hrs per day run time in a peak month for a properly sized unit at a 3,000Watt draw. The AC alone would use 1080KWH per month if sized to run 12hrs per day in a peak month. At 10 cents per KWH that's $108 for AC alone. This doesn't include any other use in the house or the base meter charges/taxes/fees.

Given that scenario, my high bill would run around $168. That would be great! Then if I left the house during the day... say, if I got a "job"... I could use setbacks and save more. Probably not gonna happen, but it is something to think about.

What do you figure the 12 hour daily cost of A/C alone should be for a 3.5 ton?

[udarrell]

If it's true that "increased evaporator airflow heat-load" from hot, moist attic air could trip the switch, you may be onto something!

Although I had the duct leaks identified and sealed, including my one return directly through the wall under the ahu stand, one contractor who later did a Manual J and further leak testing (in preparation for his new equipment quote) determined there is still a 17CFM leak at the return that needs to be sealed.

This space under the ahu is "unfinished", that is, the wall studs below the top of the stand are not covered by drywall. The contractor who sealed the duct leaks attempted to "seal" the space with ductboard, but apparently his efforts were not 100% effective. I would guess the 17CFM of leakage would allow attic air to leak into the return.

With a less restrictive MERV 8 filter, the suction from the return would pull more air in from the conditioned space in the hallway where the return filter grill is. With a more restrictive MERV 10 (Honeywell 4") or MERV 11 (1" pleated) filter, suction from the hallway would be restricted and more air would be pulled in through the "leak" from the hot attic.

Given the poor, but constant, condition of the condenser coil, this added heat load might just be enough to trip the high pressure switch.

Does that make sense?

Yep, makes absolute sense; your reasoning is on target!

[tedkidd]

With a less restrictive MERV 8 filter, the suction from the return would pull more air in from the conditioned space in the hallway where the return filter grill is. With a more restrictive MERV 10 (Honeywell 4") or MERV 11 (1" pleated) filter, suction from the hallway would be restricted and more air would be pulled in through the "leak" from the hot attic.

Wow. Another indication of insight at a very high level. Beginning to intuit how variation in static can impact leakage, and that this leakage may not be a linear relationship.

Now connect that concept to equipment size. It's the same concept from a little different orientation. The 4 ton pump is like installing a permanently more restrictive filter.

1600 cfm airflow requirement vs 1200 cfm airflow requirement means a whole lot more pressure on your whole system. Your "system" includes rooms, as well as duct, and all these things leak "liquid air" in humid climates. These are leaks that will never be 100% cured.

Rooms that have more supply than return will be pressurized. Like blowing into a paper bag, they will leak to outside. Blowing harder makes the leakage increase. The opposite effect occurs to areas that are return dominant, air from outside will be sucked in.

Measuring current ESP will help you understand if that increase represents no, little, or catastrophic design flaw. If the 3.5 ton fan is set at 1400 cfm, and has .5 static or above, don't go up on equipment without duct redesign and replacement.

[Florida Joy]

With a less restrictive MERV 8 filter, the suction from the return would pull more air in from the conditioned space in the hallway where the return filter grill is. With a more restrictive MERV 10 (Honeywell 4") or MERV 11 (1" pleated) filter, suction from the hallway would be restricted and more air would be pulled in through the "leak" from the hot attic.

Given the poor, but constant, condition of the condenser coil, this added heat load might just be enough to trip the high pressure switch.

Does that make sense?

Yep, makes absolute sense; your reasoning is on target!

I just realized my original post has some misinformation and may be misleading. I said I was "using" Filtrete MERV 11/MERV 12 pleated filters. That's not exactly true. Actually, I had "purchased" 3 of the MERV 12's and had a MERV 11 stored in the garage, with the "intent" of using them when I replaced the last of the Flanders MERV 8's that I'd been getting from Home Depot.

When I picked up the Honeywell fc40r, I returned the MERV 12's for credit, but I couldn't return the MERV 11, which had been purchased over 3 years ago in VA.

From now on, I'll use MERV 8 or lower until I get a new system with a second return.

[energy star]

If you took the filter OUT, you would STILL be pulling air in through a duct leak in the unconditioned space, that difference is not tripping the high pressure switch on the outdoor unit.