Asking for a sanity check...

[didolgi]

Hi -

From general browsing of this forum I think this would be the right place to ask this question, but if not please just let me know.

First some basic info:
Location: San Fernando Valley, CA
House Built: 1954
Air Cleaner: Honeywell Electrostatic (big box with wires and fins)
Furnace: Lennox Pulse NG - installed 1984
A/C: Lennox 4ton installed 1986

I've had a problem with my furnace cycling since least season and it seems to have gotten worse this year. It does heat the house, and the blower runs just fine, but I can hear the pulse jet cycling on and off every few minutes. I have the same service company for 20+ years (they installed) and I do trust them, but this is one of those times I want to do a sanity check. Also, both systems have been trouble free for 20 years.

At first they thought it was low gas pressure under flow, as the static pressure was fine, but pressure while the furnace was running was "right at the minimum" line for this model. I had the gas company install a new regulator and that did raise the pressure to a safer value, but the problem came back this winter.

The tech came out a few days ago and watched the safety cut off climb to its max limit and shut off the gas. It cooled and cycled again. At least now we know why its cutting out, but I'm not 100% comfortable with his reason for the cut off, so I just wanted to ask if this is something that is typical or not.

My A/C coil is installed directly above the furnace and is over the years pet hair, dust, etc. has clogged the coils to the point where airflow is being blocked and the furnace if overheating. In the service record two years ago they removed the blower and cleaned the fan as it was dirty, I wasn't home at the time so I can't say how dirty it was.

They are giving me two options
1. remove the furnace and coil for a REAL cleaning - cost is in-line with what I'd expect for the labor involved.
2. remove furnace and A/C and install new. Reason being it doesn't make sense to remove and re-install 20+year old equipment, no matter how reliable. - I am going to get two competing bids, but I know from prior work they aren't the cheapest company in town, but 20+years builds lots of trust.

I do think I agree with remove and replace given that I know that A/C units and blowers are more efficient then they were 20 years ago. My Pulse has a 92% AUFE so I'm not really gaining anything there. This would also give me the opportunity to relocate the unit into a connected garage and regain some space for an upcoming bathroom remodel. I just really didn't plan on spending this kind of money now.

I guess what I'm asking from forum is given that I have an Electrostatic Air Cleaner (was cleaned about 2-3 times a year), and I do use the A/C or Heat, or just Fan mode OFTEN. I do have several cats (while my aunt was living with me it was more then several) Does it sound reasonable for the coils to have become plugged and cause this problem?

For what its worth The recommended replacement units are
Lennox XC21 - (I use LOTS of A/C)
Lennox G61V
Lennox PMAC-12C/20C Hepa Filter.
I intend to live in this house for many years to come so buying high efficiency units is a good value for me.

Sorry for the long winded post, but I'm just looking for some reassurance about a major investment in my home.

Thanks for any feedback.

[t527ed]

some of the dirtiest systems i have seen were the oneswith electronic air cleaners on them......:(


i would go with cleaning the coil before replacing a working high efficiency system.

did they pull the blower and check the secondary hx for dirt?


without seeing the install its hard to say how hard pulling the evap coil to clean would be.

if you do go new the system quoted is nice but i would go up to the g71 furnace......;)

[DanW13]

Is the current equipment the proper size for the home ? If the equipment is on a dirty side where the EAC isn't keeping everything as clean as it should you might want to upgrade the EAC with wither a Aprilaire 5000 or an Infinity air cleaner these 2 are the top 2 EAC's on the market today they use a pre filter 2" media filter instead of those wire mesh pre filters which will probably help with fitering the air alittle better than what you currently have. As for upgrading the furnace being that it is a 92% now and going up to a 96% will save you some more but maybe a more efficient than your current equipment and you might be able to downsize the furnace if you go with a modulating furnace so you could possibly save there as well. Just something to think about ask your current company that does your maitience now to perform a load calc on your home and see what size equipment the house needs, you may be oversized now or undersized or it maybe fine.

[STANCILHVAC]

some of the dirtiest systems i have seen were the oneswith electronic air cleaners on them......:(


i would go with cleaning the coil before replacing a working high efficiency system.

did they pull the blower and check the secondary hx for dirt?


without seeing the install its hard to say how hard pulling the evap coil to clean would be.

if you do go new the system quoted is nice but i would go up to the g71 furnace......;)

LIKE you say with not seeing it its hard to say--but why pull the coil to clean it?Most coils can be cleaned in the case,just take the front panel off---and all that clogged pet hair is definatly a problem,has the heat exchanger been checked as with that age and the restriction on the air flow caused by the blocked coil---i cant see it being far behind if its not already cracked ---and then you have a 20 year old ac unit that the compressor is probably not far behind--again especially with that clogged coil--at the most,i would just have the coil cleaned and then be prepared to have those units and coil changed before long---even though it may keep going for a good while ---who really knows---after 20 years you can get ready for more problems which will eventually add up to more than it was worth to try and keep it going---thanks

[Kevin O'Neill]

Sounds like low air flow. Removing the indoor coil for a good cleaning (after 20 years) sounds like a good idea. I would also pull the blower and clean the secondary heat exchanger in the furnace. In fact, since it is the first coil in the system it is likely to be the dirtiest, so I would do that first.

Good luck.

[heaterman]

While cleaning will most likely solve the problem, the associated equipment IS 20 years old, no way around that fact. The furnace you have WAS rated at 92% but most likely has slipped a few points. Your AC system is where the real potential problems and definite savings are going to be. I think the smart money will be in replacing the entire system. If you were not experiencing problems, that would be one thing but you are looking at a sizable cost to fix what you have. Put that money toward a new system, you won't be sorry. Whatever the system, 95% furnace and 15 SEER AC (think about an add-on heat pump also) should be the minimum starting efficiency.

[didolgi]

I can't thank you all enough for the replies especially on New Years!

You've all confirmed what was my real concern that after 20 years the coil could be so dirty that its restricting air flow. I was present when the furnace and coil were installed, and I can assure you there is no way to reach the coil without pulling the furnace. The front plate is partially obscured by the ceiling so the furnace has to be moved out while the coil is braced and then lowed down. In addition to that the PVC vents for the Pulse are running directly in front of the A/C coil so those would have be cut and repaired. The house was built without A/C and it wasn't a great retrofit (previous owner). The closet its located in a very tight fit.

I know installing G71 might save me fuel costs in the long run, but heating has never been a large part of my bill. I'm an IT professional, and I have several office sized computers and they kick out plenty of heat :) Also winters are fairly mild here and its unusual for me to need heat more then a few weeks a year. At 11:00 its 72 in my backyard on the first of January :)

I'm going to use this opportunity to relocate the unit into the garage so future service will be easier and I'll regain some space for a future bathroom upgrade.

Oh, and yes I plan to dump that electronic air cleaner and install one of the Lennox HCPMAC-12c/20c.

Thank you all again for the great responses and I wish you all a Happy New Year!