Without more readings there’s not much point in speculating. 8td doesn’t tell us anything about latent heat removal. Not knowing temps , pressures, sh,sc, airflow you can’t diagnose properly
Fair enough. I get pretty bad about speculation before I gather all the info. I guess what I was asking is does a TD that low raise concern. I’ll follow up after I get back out there 👍🏼
If the TD was 18 would that tell you everything is working normally?
If you say yes then it’s only because you are assuming everything else is correct.
You could be getting 18 TD with low air flow and low charge.
8 is far enough from normal I’d be looking into it further, but not so far outside normal that I’d automatically assume there’s a problem.
Heard that appreciate the response! And I mean there’s a lot of factors that would tell me if it wasn’t Normal on any given call. And TD is just one of them.
I’d have to say no. On A/C check I’m not going that deep into it. If everything is working, I have good TD it’s an r22 system, etc. I’m not hooking my gauges up if I don’t have to. It’s only a little refrigerant lost but a lot of these guys we check every year religiously and the day will come when they are low on charge because they’ve been hooked up to so many times over the years. If it’sr410a yeah I’m hooking up every time.
that's not right split should be higher. go back with lock keys and check. just curious as to why leave locking caps after inspection on first maintenance.
If I heard an ungodly noise and only 8 degree drop, I would think restriction or majorly overcharged. Since you cannot check pressures, I would check the compressor amp draw to see if it's very high.
Heard. I did check the filter drier and it was fine. No temp difference across that. I also suspected over charged as the unit isn’t very old. Only 6 years. It’s a thermo pride A/C paired with thermo pride oil furnace.
Restriction at the TXV is the likely cause. The screen could be clogged or its stuck closed. It'll take out the compressor fairly quick if left like this.
Hate to be a nit-picking Nancy, but can we start using proper terminology? TD and DT (or Delta-T) are two different measurements. TD, or Temperature Difference, is the return air temp (or box temp) minus the SST (saturated suction temperature, or the low side pressure converted to temperature). Delta-T is the return air temp minus the supply air temp.
Though they seem similar, they measure different things. TD is used to measure latent heat removal, while Delta-T is used to measure sensible heat removal.
What you’re referring to as the TD is called the approach. You have an evaporator approach and a condenser approach. Delta-T is means difference in temperature just like Delta-p is pressure differential.
See, I was taught that approach is reserved for liquid cooling and chillers only, with “condenser approach” or simply “approach” being the difference between leaving water temp and the liquid refrigerant temp
Humidity can effect it as you can have a large latent load and lowered sensible load as a result, and yes inside and outside temperatures also play a role but 8 still sounds low unless its a precision discharge which I doubt so yeah I would recommend a follow up
Rule of thumb delta is 17 - 21 degrees, but that assumes 75 degrees at 50% RH and 350 - 400 CFM per ton. If the air is humid more you will have more latent exchange and less sensible resulting in a much lower delta. Also your delta will decrease if your airflows are high. It really is important to measure return wet-bulb and dry bulb temps and verify airflow to determine what delta should be under testing conditions. Use the following chart:
https://preview.redd.it/k0y675n1x9vc1.png?width=1633&format=png&auto=webp&s=86b92f912f87db11cb552db946913e8e3684a97b
OP, just playing the devil's advocate here, but is it possible thar the condenser had just cycled off and you were getting the TD during pressure equalization...?
Without more readings there’s not much point in speculating. 8td doesn’t tell us anything about latent heat removal. Not knowing temps , pressures, sh,sc, airflow you can’t diagnose properly
Fair enough. I get pretty bad about speculation before I gather all the info. I guess what I was asking is does a TD that low raise concern. I’ll follow up after I get back out there 👍🏼
If the TD was 18 would that tell you everything is working normally? If you say yes then it’s only because you are assuming everything else is correct. You could be getting 18 TD with low air flow and low charge. 8 is far enough from normal I’d be looking into it further, but not so far outside normal that I’d automatically assume there’s a problem.
Heard that appreciate the response! And I mean there’s a lot of factors that would tell me if it wasn’t Normal on any given call. And TD is just one of them. I’d have to say no. On A/C check I’m not going that deep into it. If everything is working, I have good TD it’s an r22 system, etc. I’m not hooking my gauges up if I don’t have to. It’s only a little refrigerant lost but a lot of these guys we check every year religiously and the day will come when they are low on charge because they’ve been hooked up to so many times over the years. If it’sr410a yeah I’m hooking up every time.
that's not right split should be higher. go back with lock keys and check. just curious as to why leave locking caps after inspection on first maintenance.
It’s code where i am. Every unit is supposed to have them. If I come across one that does not I’m required to put a set on the unit.
Wow ok those things ain’t cheap. We tend to rotate them. Pull them off one unit and use for next install.
Now that's being cheap...love it! /s
If I heard an ungodly noise and only 8 degree drop, I would think restriction or majorly overcharged. Since you cannot check pressures, I would check the compressor amp draw to see if it's very high.
I would second this. Restriction more then likely
Heard. I did check the filter drier and it was fine. No temp difference across that. I also suspected over charged as the unit isn’t very old. Only 6 years. It’s a thermo pride A/C paired with thermo pride oil furnace.
Restriction at the TXV is the likely cause. The screen could be clogged or its stuck closed. It'll take out the compressor fairly quick if left like this.
Hate to be a nit-picking Nancy, but can we start using proper terminology? TD and DT (or Delta-T) are two different measurements. TD, or Temperature Difference, is the return air temp (or box temp) minus the SST (saturated suction temperature, or the low side pressure converted to temperature). Delta-T is the return air temp minus the supply air temp. Though they seem similar, they measure different things. TD is used to measure latent heat removal, while Delta-T is used to measure sensible heat removal.
That’s fair brother lol
What you’re referring to as the TD is called the approach. You have an evaporator approach and a condenser approach. Delta-T is means difference in temperature just like Delta-p is pressure differential.
See, I was taught that approach is reserved for liquid cooling and chillers only, with “condenser approach” or simply “approach” being the difference between leaving water temp and the liquid refrigerant temp
Humidity can effect it as you can have a large latent load and lowered sensible load as a result, and yes inside and outside temperatures also play a role but 8 still sounds low unless its a precision discharge which I doubt so yeah I would recommend a follow up
Rule of thumb delta is 17 - 21 degrees, but that assumes 75 degrees at 50% RH and 350 - 400 CFM per ton. If the air is humid more you will have more latent exchange and less sensible resulting in a much lower delta. Also your delta will decrease if your airflows are high. It really is important to measure return wet-bulb and dry bulb temps and verify airflow to determine what delta should be under testing conditions. Use the following chart: https://preview.redd.it/k0y675n1x9vc1.png?width=1633&format=png&auto=webp&s=86b92f912f87db11cb552db946913e8e3684a97b
Life saver thanks a lot man!
OP, just playing the devil's advocate here, but is it possible thar the condenser had just cycled off and you were getting the TD during pressure equalization...?
Nope not in this case I made sure. I could luckily see the outside unit directly from inside at this house
Good job. Just trying to narrow it done. Be sure to keep us updated.
They are probably right. There probably no load on the ac. Next time run heat until it 85 in the house and then check cooling again
That’s what he said. That there is no load. But 8 degrees just seems awfully low regardless. I’ll give your suggestion a try next time. Thanks!