PDA

View Full Version : Need Advice on Refrigerant Line Diameter on install that was just done!







mcu
26-02-2008, 04:28 PM
Hi,

I need some advice on the refrigerant line size on our install. Here is the story....We had a 3 ton heatpump unit and after a few months we discovered that it was not producing enough and installer agreed to just swap it for a 4 ton and pay a little difference. This was all done and the new heatpump is working now. My concern is that with the 3 ton, 7/8 lines were needed. for the 4 ton, Goodman, recommends 7/8 up to 24 feet and 1 1/8" from 25-50. We have 30-33feet on line in all. The installer assured me that he spoke to Goodman and they assured him that if that was an issue the heatpump would make a lot of noise and overheat.

I need your opinions on this guys. Would you guys replace them? I don't want to have issues in a couple years. If it is ok though, I don;t want to spend the extra $$ and time in fixing something that will not cause any problems.

what problems or energy loss can this cause, if any?

Thanks

Argus
26-02-2008, 04:56 PM
.

In general, packaged A/C manufacturers are specific about the size and length of interconnecting piping because it can impact on the performance and ultimate service life of the unit.

In my experience, they reserve the right to withdraw warranty if their recommendations are not followed.

We'd be unwise to comment in this forum on your installation without seeing it, so why not contact the manufacturer direct and ask them about the pipes before you enter a dispute with your installer?


.

US Iceman
26-02-2008, 05:03 PM
...if that was an issue the heat pump would make a lot of noise and overheat.


The smaller suction line can negatively impact performance a little bit with the larger unit capacity, but...noise and overheating??? I don't buy this argument at all.

You did not mention the liquid line, which must have similar issues also I would guess.

Springbok
26-02-2008, 06:32 PM
True what Argus mentioned about the manufacturers being picky about the pipe lengths and matching the correct size piping to the correct size unit.Upsizing the unit and keeping the existing piping could have an effect on the performance of the unit,keeping in mind in the long term.Best to contact the manufacturer with the correct specs...

mcu
26-02-2008, 06:38 PM
liquid line 3/8 as recommended by the manufacturer. Goodman told me to contact my installer and that they offer no tech support to the consumer.

Argus
26-02-2008, 07:02 PM
liquid line 3/8 as recommended by the manufacturer. Goodman told me to contact my installer and that they offer no tech support to the consumer.

Well, Goodman is a company that is unknown in this part of the world and seem to be very unhelpful; it's as if they smell a dispute in the offing.

So, what do we have? a 4 ton split which works out at about 12 kW, give or take a little.

3/8" liquid line sounds about right, though you may see 1/2" in some units at that capacity.



I expect that most of the installation is over one or two floors, so the lift is not drastic, but why not describe the layout for us? Is it cooling only or a heat pump?

In any case, you need to consider two things with suction sizing:


The effect of the extra length and size on the resistance to flow, because it can impact the performance of the unit

The ability of the pipe to maintain sufficient gas velocities at reduced load conditions so that oil can be returned to the compressor.


If the effect of the pipe sizing on both these is favourable, then you probably don't have a problem, but do please check the situation with regard to warranty.

Is it held with the installer or the manufacturer?

Just to give you a flavour of practices in the UK, the overwhelming majority of small split systems in this part of the world are Japanese in origin and 50 feet is not considered a particularly long pipe run. 20 feet is almost a back-to-back installation.

We normally deal in runs up to 50 or 70 Metres, much of which may be vertical and a typical suction line on one of these installations at the capacity you have would usually be 3/4". Some of these manufacturers may recommend an increase to 7/8" above 50 Metres.

To demonstrate their confidence, installer's warranties here start at 3 years and may be 5 years from some manufacturers.

.

SteinarN
26-02-2008, 07:15 PM
Is this an AC and heat pump? If so, the large pipe is the compressor suction pipe in AC mode. If this pipe is smaler than required, you may be experiencing some loss of cooling capacity, but it will not affect the useful lifetime on the system. In heat duty the large pipe is the compressor discharge pipe and its necessary size is smaler than the compressor suction pipe. No loss or adverse effects arises in heat pump mode due to a slightly smaller "large" pipe than required.

mcu
26-02-2008, 07:17 PM
yes its a heatpump with aux electric furnace heating. Its for a 2 story home.

NoNickName
26-02-2008, 07:33 PM
I don't think that 7/8" for 24 feet would make any difference is length is extended to 30 feet. One would also consider that the plant was already in place at the time of the swap.

Lowrider
26-02-2008, 07:50 PM
Is the length mentioned in the manual including bends and hight difference?

Because in some cases the lenght is not the problem, but the hight difference and the number of bends are!

mcu
26-02-2008, 08:00 PM
The manual does not say anything about bends or elevation. The installer's distributor says that its not a problem since the length is not that much more over 24 ft, but goodman says they should be 1 1/8". The installer seems like an OK guy and not trying to impose that he is trying to cut corners, but just not sure who to go by. I don't want to spend a few hundred dollars more for cost of piping, but i want to be sure it does not cause any probs for me in future.

He is coming over later today to show me readings and all, but thats all pretty chinese to me :(
what can i do or check to make sure it will be enough on those hot summer days?

Lowrider
26-02-2008, 08:46 PM
Usually the manufacturers give the equivelant lenght of pipe and that's then including elevation and bends.

If the machine can run fully loaded and reaches it's dT in heat mode, no worries!

Manufacturers usually built in some tollerance in the length, so this "little" difference, imo, would not make any difference. It's roughly from 12 kW to 14 kW.

The Viking
26-02-2008, 09:24 PM
Without ever worked on Goodman stuff,

I would say that the only thing you as an end-user can do to check things would be to measure the temperature difference across the indoor unit.

Turn the unit up to maximum heat, the fan speed to max. Then remove any restrictions on the airflow and measure the temperature before and after the indoor unit.
This difference should be above 22 F.

Another measurement of interest for us here on the board would be the temperature of the "thicker" pipe by the outdoor unit (after some time running in heat mode)

Then check the temperature difference across the indoor unit again in cooling mode.

Good luck,

nike123
26-02-2008, 09:44 PM
I need your opinions on this guys. Would you guys replace them? I don't want to have issues in a couple years. If it is ok though, I don;t want to spend the extra $$ and time in fixing something that will not cause any problems.

what problems or energy loss can this cause, if any?

Thanks

Does your outdoor unit is above or below indoor unit?
If it is below and pipes are layed out in good manner, then you probably should not have any problem, only maybe slight drop in capacity (<5%). If, on the other hand, you have outdoor unit above indoor unit, then you could have some problems, and that need attention of some competent engineer who could asses layout and other relevant factors and give you advice based on good engineering practice.
Every manufacturer give their safety operating window, whose boundaries could go wider, if someone competent take in consideration all operating and construction conditions.

frank
26-02-2008, 09:46 PM
The manual does not say anything about bends or elevation. The installer's distributor says that its not a problem since the length is not that much more over 24 ft, but goodman says they should be 1 1/8". The installer seems like an OK guy and not trying to impose that he is trying to cut corners, but just not sure who to go by. I don't want to spend a few hundred dollars more for cost of piping, but i want to be sure it does not cause any probs for me in future.

He is coming over later today to show me readings and all, but thats all pretty chinese to me :(
what can i do or check to make sure it will be enough on those hot summer days?
If it's not a problem, i expect he won't have any problem putting that in writing for you so that, later, if required, you can show the written statement to Goodman for your warranty repair.

What refrigerant are we talking about here?
So far we've had lots of reference about velocities, oil return, elevation, delta t, over heating, noise etc but without knowing what gas the system is using it is difficult to give any sort of informed advice.

mcu
26-02-2008, 09:47 PM
he measured the outside on the big pipe and it was 130F. the pressure was at 175-180 at 35F outdoor temperature. He brought me a chart and it showed that what it should be at that outdoor temperature. The expanded heating chart stated that MBh should be 20.7 but we had 34...he said more is better. Its lower we do not want.

Does this all sound right and make sense? The system uses r-22
Temp at the vents are 95-100F

Toosh
29-02-2008, 10:46 AM
Hi MCU here ia a site where the guys install what you have be sure to register and can take part in the threads
http://hvac-talk.com/vbb/showthread.php?t=161872

Regards norm

ruvy frank
29-02-2008, 01:38 PM
mi advice is for you to consult the manufactuereer. bcoz you might end up foking money on nathing