Is there a limit on how long of a extension cable I can use? GSHP system is being put in and they are using a 100A subpanel about 25 feet away (which will have 3 heat pumps and a hot water hybrid electric heater)… I’d really like to be able to monitor each unit individually (and my understanding is the symphony waterfurnace system doesn’t do real time electricity monitoring). I think ideally I’d run the extensions in conduit together.
25’ is generally OK. I have used simple headphone extensions with good results. Quick look turned up this source which looks fine at a reasonable price. They also seem to have them in about 5’ increments, so once the branch panel is in, I’d run a string to be sure of the needed length.
Running in conduit is good, especially grounded metallic. Don’t undersize, the cost of larger EMT is minimal.
I haven’t actually done it, but I don’t believe you will have a problem. Many installations have several feet of 10 or more CT cables running in conduit with no reports of problems.
The previous wisdom on this subject was heavy on theory and light on empirical results. To flesh it out I got a load of headphone extensions tried them out. Putting two identical CTs on the same primary conductor, I looked for any observable difference with various length extensions on just one of them. I could find no difference. I did not test for any interaction between two or more extensions, but you will be in a position to further this body of knowledge by posting your results, which I have high confidence will be successful.
Induced noise from high-current conductors in close proximity are still a potential noise issue. That’s why I mention grounded EMT rather than the plastic conduit that I see many using appropriately for short runs away from obvious high-voltage wires.
Thought I’d share my experience (frustration) with cable extensions, particularly since I don’t see any reviews of the monoprice cables on the forums. I ordered 4 6’ inexpensive extenders from ebay, twice. Of the first 4, 2 worked, 1 worked to transfer music from my phone but not with the CTs, and one didn’t work at all. Of the second 4, all worked to transfer music but not with the CTs. So I ordered 4 of the monoprice 6’ cables linked above. Unfortunately I didn’t look closely at the pics on their site first. These cables are THICK; each “cable” is actually 2 cables between the male and female ends. They might work but there’s no way they would fit in the conduit I’m using. I’ve now ordered 6 different kinds of extenders from Amazon. I only need 4 but I suspect some won’t work. I’ll report back on which worked and which didn’t.
These are well made utilitarian cords. I find that Amazon and others are typically catering to the audiophile community with gold plating and color/texture schemes that have little to do with functionality but exploit the whims of those with disposable income.
Hi Overeasy. Here’s a link to the Ebay cables I bought: Standard 3.5mm Stereo Not sure how durable it will be.
By not working, I meant that I saw zero watts on the status panel. The plugs were fully seated and the only variable I changed was the extension itself. If you’d like to experiment with them, I’m happy to donate to the cause. I doubt the ebay seller would take returns and I can’t be bothered anyway.
If the Amazon cables don’t work, I’ll give those you linked a try.
That tells me that the extensions are simply defective. Seems unlikely, but nevertheless it’s a simple device and would work somewhat. What seems puzzling is the allegation that they work as an audio extension but not for a CT.
The only thing I can imagine is that perhaps some of these are crossing the left and right channels. That would exhibit the symptom you are reporting. If you want to send me a failing extension, I’ll verify and diagnose.
I also ordered 1 I didn’t install (or test) and haven’t linked here. What I like about these 4 is that the cables are thin and the plugs small. I might have been able to run all my cables through 1 3/4" conduit if I had used these extenders from the start. They were super easy to fish through.
Thanks for following up. Interesting to know what you found. It cost me nearly as much to ship the others back to Monoprice as I’m getting refunded, but I hated to just through them in the trash. If I were to do it again, I’d just buy from Amazon, knowing I can return without questions.
Sorry, I do not. I had bought some on eBay a year or so ago and they were fine. Given they are short, I wouldn’t worry about resistance. The key factor is that the left and right channels aren’t switched, which will not work.