Help with new installation

[ardnas]

We are in the Philadelphia area, and have a rental home , in which the air-conditioner stopped functioning. When it was working, the tenant said it did an excellent job of cooling a 4-level home, even on the top level. The present system is about 25 years old and has not caused problems until now.

Two of the contractors who inspected unit, suggested replacing the blower motor, the others said to replace the whole system. All but one said to stay with R-22 refrigerant, one said to go to 410.

None of the contractors who have given me estimates made a Manual J load analysis, nor any of the numerous elements on a quality installation checklist (found on the ACCA HVAC Quality Installation checklists). They are in agreement about very little.


1. The outside diameter of the piping which carries the coolant is 3/4 inch. Is that big enough to carry R-410 coolant?

2. We have contractors saying that we should use R-22 refrigerant because the pipe is not large enough to carry 410. If it could hold 410, is there any advantage or disadvantage to using the R-22? Would the present piping, which handles R-22, be able to hold the high pressure of R410? The piping from the lower coil to the condenser is inside walls, so that cannot be changed.

3. If I install a new AC system, can the same model use either R-22 or R-410?

4. If I install an AC unit with a SEER 13, can I install with it a furnace with a higher efficiency rating? Would that make sense in an area where there is much more heating, and less cooling during the year (Philadelphia, PA area)

5. One contractor suggested a 2-stage gas valve with multi-speed blower (Carrier), others did not. What is the advantage or disadvantage of this? He is doing this so that he can move more air to compensate for the fact that there are no return ducts in the house. No one else has said that.

6. What qualities are important in a thermostat? Is it important that it include short-cycling protector? Is a scroll compressor important?

7. Two contractors said that they cannot make any measurements as long as the blower motor does not work. They suggested that we start by replacing only the blower motor. If that does not solve the problem, they will look for the next problem.

Any suggestions you have beyond these would be greatly appreciated. And we do thank you for any responses to these questions.

[DanW13]

If this is for a multi level home (4) you might want to consider have atleast 2 unit to serve 2 floors each to split the load. You should also have someone do a load calc on the home so you and they know what size equipment you will need to H/c the house. The contractor who wants to replace the blower motor and go from there sounds like he wants to nickle and dime you to death so I would probably stay away from him.

as far as having a stat that is "short cycle protector" theres no such item that I am aware of, short cyclying comes from the equipment is oversized for the amount of space heat load it has to h/c causing the equipment to run for a couple of minutes and the stat is satisfied which you do not want. You want the equipment to run for longer periods usually 20 minutes or more for the home to h/c properly.

Carrier makes some nice equipment, so do other manufacturers, so it would be in your best interest to call a couple of other contractors and ask them all to do manual J,D,S on your home and then have them price the equipment based on the load calc of your home and go from there.

[ardnas]

To DanW13: Thank you for your insight!

[BaldLoonie]

1. Depending upon capacity of unit

2. Often, the 410 units call for a smaller line

3. No

4. Yes

5. There's a comfort advantage to 2 stage, using low fire in mild weather. Not something you usually see a landlord paying for!

6. About every digital has short cycle protection. Stick with name like Honeywell or White-Rodgers. Scrolls are the latest technology. Other than Trane, which makes their own compressors, rare to see a recip these days though a few still have them in lower priced, lower sized models.

7. At 25 years old, probably not worth putting money into the old stuff. If the A/C was working when the blower motor went out, just change the furnace and wait til the A/C quits to change it. Of course everyone will say change the A/C too but you don't have to. Your money though.

[Cold Feet]

None of the contractors who have given me estimates made a Manual J load analysis, nor any of the numerous elements on a quality installation checklist (found on the ACCA HVAC Quality Installation checklists). They are in agreement about very little.

Anyone who hasn't done a Manual J is just guessing (or worse) about what kind of equipment to sell you.

Get back to the most promising bidders and ask them to do Manuals J and D and to prove it by telling you the heat loss and proper duct size for one room in the building. Walk away from any contractor who refuses to do the work.


If it could hold 410, is there any advantage or disadvantage to using the R-22?

R-22 is in the process of being phased out by law under the Montreal Protocol against ozone depletion. Production of R-22 will be restricted on January 1st 2010; it will be banned outright in 2030. If you buy an R-22 unit, getting refrigerant to recharge the system after a leak will be increasingly difficult and expensive. This alone is reason enough to buy R-410A equipment even if it means tearing up the walls to run a new lineset (pipe).

Manufacturers and contractors have every incentive to to sell R-22 units to every sucker they can find before R-22 is banned. Buyer beware.


3. If I install a new AC system, can the same model use either R-22 or R-410?

No.


4. If I install an AC unit with a SEER 13, can I install with it a furnace with a higher efficiency rating? Would that make sense in an area where there is much more heating, and less cooling during the year (Philadelphia, PA area)

Air conditioner SEER and furnace efficiency (AFUE) are completely unrelated. You can have a high efficiency air conditioner and crap furnace or vice versa.


5. One contractor suggested a 2-stage gas valve with multi-speed blower (Carrier), others did not. What is the advantage or disadvantage of this? He is doing this so that he can move more air to compensate for the fact that there are no return ducts in the house.

You must have adequate ducting for a forced air heating/cooling system to work. If you don't have return ducts then you most likely don't have adequate ducting. Ask for bids to have the house re-ducted to Manual D standards.

Variable speed blowers can compensate for poor ducting but they're not magic. No system will work without adequate ducting.


If it's not feasible to install new ducting, look at multi-split (ductless) (http://mrslim.com) or high velocity systems.


7. Two contractors said that they cannot make any measurements as long as the blower motor does not work.

What do they mean by measurements? It's entirely possible to size a new system even if the existing system is completely dead. A contractor who wants to replace the blower motor before giving bids on replacing the AC is trying to scam you.