A few years ago, I had my HVAC system replaced and recall they did a
really good job measuring, matching the new indoor and outdoor units,
and installing everything.
A friend of mine is buying a house with a heat pump. The sellers bought
a new outdoor unit, but *left the original old indoor unit intact.*
But it gets more interesting, the new unit is a Carrier "Weather Maker,"
model 38YXA024330 and says "Puron."
How can an outdoor unit made for Puron work with an old R22 indoor unit?
The indoor unit is a Synder General model BYMBO024 (no joke that's
actually the model number).
Will this setup work at all? Is there even a warranty on such a system
if the indoor unit isn't replaced? How do you measure efficiency on
such a system?
At significantly reduced efficiency, and that's if they are luck?
My understanding is the same
as yours which is that coils that are in a system that used R22 are
incompatible with R410A. Not only are there performance
differences, but R410A systems operate at significantly higher
pressures than R22, so the coils are built and tested to
withstand those higher pressures. The oils used are incompatible
so the old system would have to be completely flushed of
all the old oil. You have to wonder what else a hack that
would do this would skip.
Warranty by whom? The manufacturer of the new unit? No way.
By the hack who did the job? Possibly, but good luck getting them
to honor it.
This is a good example of what NOT to do. The sales contract
should have had a clause giving the buyer the option of negotiating
a discount off the sales price instead of having the seller make
the repair. That way the buyer could have decided what to do
and that probably would have been to replace the whole system
with one of their choosing, letting them decide the cost vs
efficiency, etc. Doing it the way it was done here, the seller is
just going to do whatever they can for the cheapest price to
get it working again. Also, in many areas there are utility or
state rebates for higher efficiency systems that can give
you a better system for a little more money. Those rebates
sure don't apply to half a system.
As the buyer, they should get the system inspected again
by a reputable contractor of their chosing. Hopefully they
can get a written opinion that it's a hack job and then
demand the above discount from the selling price.
Depends on exactly what left the indoor unit intact means. You can
simply replace the A coil on the inside unit and leave the rest alone
and that would be fine.
As to making the original A coil work with the new r410a outside unit
there's some controversy there. A lot of people argue against that.
However on the other side of that issue Goodman sells cased A coils
that are the same and are used for both their r22 and r410a systems.
And it is common for a single A coil to match a range of outdoor units
by just changing the orifice or txv.
All that happens in the A coil is the release of the high pressure
liquid refrigerant to a larger area where it returns to being a gas.
And it is circulated through the tubes to pick up heat from the inside
air passing over them.
Some people install an oversized A coil to try to increase efficency.
The more time the lower temp refrigerant is exposed to the higher temp
insode air the more heat it picks up. One of the biggest noticable
changes in the outside units as they increased efficiency is the same
thing, larger coils. Just compare any newer unit to an older one.
They are all bigger for the same tonnage.
However, knowing what the results of these mismatches are
statistically is anyone's guess. That's the main arguement against.
If you install a complete sytem then you have something that was
tested as a unit in a lab somewhere.
Since it's not a furnace, I guess basicly it's the air handler. You
probably find an R410A coil compatible with the outdoor unit. But if
you look at pricing the whole thing, it would probably make more sense
to have just replaced the entire system because it's probably not a
lot more for the whole thing. It also depends on the age of what's
there, any utility rebates that you could get on a complete system
versus just changing part of it, etc.
But again this is a good example of why when buying a property
you want a credit for things the inspector finds instead of having
the seller fix it. That way you can decide what's best based on
your criteria and situation. We know what the seller's criteria is.
Fix it as cheap as possible to get it working.
Another point. It's not clear if this repair was the result of a
home inspection or not. If it was, one obvious thing to do is
ask the home inspector what he thinks about how it was
done. May not be too productive, as most of them just
say "this ain't working, needs to be evaluated by an HVAC
guy", but it can't hurt to ask.
Nuts. Totally nuts.
You purge all old refridgerant, connect the lines, throttle the compound
gauges regulator and the refrigerant cylinders regulator to purge
again. Pressurize the system to a point just below the condensing
pressure, turn the unit on, add refrigerant until the pressure in the
low pressure side reaches the design operating pressure, check the
superheat, and make sure that the sight glass is clear.
I suppose in some places the indoor part is just an air handler. Here back
up heat strips are required so you have those, the controls, the air handler
Why replace all of that if the proper coil will fit in the old shell?
I just replaced my unit here this year. I sure did not buy a new furnace.
We just replaced the A-coil and the condenser unit.
The average homeowner looks at the old shell and does not see the new coil
inside the unit so they think nothing was done inside.
Please come visit http://www.househomerepair.com
If it's 20 years old and you can get a whole new unit for
a few hundred dollars more, that would be a good reason.
And if rebates are available from the local utilites, govt,
etc, in most cases they are going to require that the whole
thing be replaced. That's because the system has to be
certified by the manufacturer to meet certain efficiency
standards to qualify. Factor that in, plus any rebates
from the manufacturer, etc and the cost of a
whole new heat pump system versus replacing just
the outside unit and the coil could be small.
He doesn't have a furnace so the cost difference of replacing the
whole unit isn't going to be as much.
That's a good point. It's possible that's what happened
in this case. We don't know on what basis they concluded
that only the outside unit was changed.
Why replace the coil in the first place?
It's got no moving parts!
What's the total cost (including labor) to rip out the old coil and
replace with new?
What is the actual, practical benefit of doing that?
If it ain't broke, don't fix it.
The coil has no moving parts. Fer christ sakes, you might as well say
that the copper lines running between the air handler and outside unit
should be replaced while your at it. Because new lines are always
better than old lines - right?
Sounds like you've never seen one rusted and
falling apart. As for reasons, I just gave a list.
It's not just the coil. It's the coil plus the outside unit that we
are talkiing about in this case. That's
the cost that should be compared to replacing the whole
heat pump system. And as I stated, factor in any rebates from the
manufacturer, utilities, tax incentives, etc. Those almost
always apply only to COMPLETE SYSTEMS. I think when
you do that for a heat pump system, it's not much more
for a whole new system which is then brand new and
has a long warranty on everything.
Already listed the practical benefits.
So, you're OK with putting an R410A outside unit
on an old R22 system regardless of the age or
how little it might actually cost to replace the whole
I replaced my system recently and used new lines. For $200
and given they were 27 years old, passing through concrete
blocks where they can't be inspected, I think it was the right
thing to do. Three of the contractors who quoted the job were
of the same opinion. One, the low bidder, wanted to re-use
the existing lines.
We have changed out systems and converted the old gas furnace to
emergency heat for the new heat pump. There is a control mod on
the market to do just that. The pressures for the new R410a
refrigerant are much higher than the old R22 systems so it's not
likely anyone will try to reuse an evaporator coil but the line
set could be OK. I would flush the line with nitrogen and internal
system cleaner if I reused it to get rid of any mineral oil and
contamination. As long as the old air handler produces acceptable
CFM for the R410a evaporator, there is no reason to have to replace
it unless it's worn out.
That sounds like the name of the furnace/air handler. The new coil could
be sitting on top of the old furnace which shouldn't be a problem
if the air handler is working and has adequate air flow. Check to see
if there is a new A-coil atop the old furnace,
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