Anonymous wrote:Thank you, electrician friend! So our current setup is hydronic, heat-only, and we have ducts and 3 separate air handlers. The air handlers will be replaced 1-for-1. The tankless water heater that heats the water for the hydronic system runs on gas.

The HVAC guys are proposing various things, but the least ridiculous proposal involves 35A + 30a + 30a for 84,000 BTU total across 3 units (adding AC coil for each air handler). So same 84,000 BTU as you’re calculating with a high SEER unit. Now I’m wondering if this design is also constrained by the 3 separate air handlers and duct setup. The house is 2-stories but mostly 1 room deep so it’s pretty stretched out. One of the guys was adamant that higher BTUs and less air handlers/AC units would not work and would be less efficient.

I agreed with electrician till you posted this. 3 units is a big load.

Discussing with ChatGpt is been helpful for me about remodeling issues specially before discussing it with trades people.

OP with an update:

Electrician #1 did a load calc and says we are at 95a for the entire house and should upgrade the panel but not the service. Otherwise he was quite vague.

Electrician #2 came up with a similar load calc and is completely confident that we can install a SPAN panel and add a heat pump with cooling coils that match with the air handlers and that even then we will still have power to spare.

Electrician #3 is not confident that anything short of an upgrade will work and is coming out next week to do further investigation.

I am also in touch with our city power company representative for the area and he is working on assessing if we would be eligible to return our service line to an aboveground connection to simplify the upgrade and the impact on city infrastructure. He was very helpful and easy to talk to, so it was a lesson in not making assumptions about employees just because they work for a difficult-to-navigate bureaucracy. Our city apparently requires a very different engineering approval process if we were attempting an EV charger install + upgrade. His advice was “find another way if you think you’ll ever get an EV because that will make the time for an upgrade way longer than you have.” I don’t know if this is specific to our municipality, but good to find out in advance if you are considering an upgrade.

Finally, it appears that the line is buried in conduit but that is 2”, not 3”, and no longer up to code, so we would have to replace the entire line + conduit all the way to the transformer at our expense.

Everything I wanted to know! I cannot thank you enough for giving me the facts and vocabulary to navigate these conversations. I’m not joking when I say that I was considering pausing bids and enrolling at the local technical college because I feel like I don’t have the words or understanding I need to make the right choice. And it’s also very interesting.

If you see this thread pop up in the next few weeks, please do check it. Hopefully I’ll have a plan by then and I’ll post an update in the hopes that it can help others.

Thank you for sharing your expertise in such an intelligent and respectful way. It is a gift to learn from a patient expert and I hope the generosity you’ve shared with me is returned to you some day.