Viewing a single comment thread. View all comments

pixel_of_moral_decay t1_j25ooqm wrote

Over the weekend it looks like it was inadequate. I keep things a little cooler but my PTAC didn't even run constantly those days.

For the rest though, that looks way too much like short cycling to me. Inadequate insulation might be part of it, but I'd try increasing the temperature differential.

Most things are not terribly efficient at the start/end of the cycle. The more on/offs you have, the more time it's spending in that state. Either that or the thermostat is too close to the unit and as the heat rises the cooler air in the rest of the room gets to it pretty quickly.

I found increasing my differential to 1.5-2 degrees vs the standard of 1 to be a game changer efficiency wise. Much less starts/stops. 1-2 degree jumps/drops in temperature in the room aren't a big deal, I'm not that sensitive. Not to mention it's a lot less stress on the system not doing so many starts stops. Oh and noise is better too. I don't care about white noise in the background. Starting/stopping however can get annoying.

The other thing to look at is fan speed. If the fan speed is too low, you can end up with a warm pocket in the room, then when the system turns off the pocket moves and it starts back up. Higher fan speed will distribute air better resulting in less cycles and more consistent temp. Smarter thermostats can even go high for a bit then go low to maintain like the ecobee.

3

Blecher_onthe_Hudson OP t1_j25w9pb wrote

Thanks for thoughtful response. The system is kind of idiosyncratic so some of what you say doesn't apply. Short cycling is an issue with something like a steam system or PTAC, but this is actually a small apartment being heated by its water heater!

The cycling is the on/off of the fan in the wall heaters, not the cycling of the water heater itself. The challenge it had during the cold weather wasn't the BTUs of water heater but the amount of radiation it could transmit through the radiators. I'm using a Nest thermostat provided by PSEG for free, I haven't seen a setting for temp differential but I can hunt around for it.

It's also interesting what you say about the fan noise. This is something new to me, I'm used to passive radiators and I've been unsure how to approach it. These units actually have two fan speeds, but the higher speed definitely seems intrusive to me. I'm curious how loud a PTAC is, what would you compare it to? I'm assuming that a quality residential PTAC isn't as loud as what I've experienced in motels.

3

pixel_of_moral_decay t1_j269mnb wrote

I’d suggest playing with temp differential if possible. There’s pros and cons to high vs low, it really depends on your priorities. Noise vs energy efficiency vs equipment stress. To me the old standard of 1F is excessively tight. Heating wise I’m ok with 2F, which means it starts/stops a lot less.

As far fan noise, that’s a trade off too. In my experience your brain ignores steady sounds pretty easily. I forgot earlier I had the dryer running until the cycle ended. That hum is just something we filter out when we get used to it. On/off however is jolting. You don’t really adjust to that. Modern better systems are obviously quieter than those hotel units but never silent. That’s a lot of air moving through a small space. Physics comes into play. Central heating with multiple registers each with less airflow will be quieter. But still not silent. You still hear it turn on/off. But less airflow makes it less obvious.

I don’t think there’s hard rights/wrongs here. It’s just what you prioritize in what situations. My bedroom I care more about noise, so I overcool it at night when it’s time for bed, then have a higher differential and low fan speed. That lets me keep it cool in the summer and not turn on so much. In the living room I let the thermostat control the fan speed so it will be low if possible (maintaining temp mostly). I care less about noise.

2

Blecher_onthe_Hudson OP t1_j26awxp wrote

>I’d suggest playing with temp differential if possible. There’s pros and cons to high vs low, it really depends on your priorities. Noise vs energy efficiency vs equipment stress.

Like I said, because it's just a fan not a compressor system or boiler, there's no efficiency hit or equipment stress to the cycling. The fan noise is literally like having a table or box fan in the room, but some people are more sensitive to noise than others. My MiL freaks out about noise, she runs from the kitchen if you turn on the range hood! But she does the same if I turn on the lights, it's a great way to get rid of her...

2

robin_tern t1_j25xhpb wrote

So you can't increase the boiler temperature without risking scalding your tenants? I imagine there would be a way to increase the heating water temperature separate to the house hot water, even on a combined system.

My house was struggling to get to 65 with the boiler set to the default 180 degrees, I increased to 210 and things got much better.

Robin.

1

Blecher_onthe_Hudson OP t1_j260yu9 wrote

The tank cannot be increased beyond where it is set. The water heater has a mixing valve for the domestic hot water so the tank temperature is irrelevant to it. If your water heater doesn't have a mixing valve it should, not only does it create effectively more hot water from your tank, but your tank should be set to at least 130 to eliminate the possibility of legionella breeding in your system.

2

robin_tern t1_j25qcbl wrote

A good response for those with PTAC.

OP has hot water boiler with baseboards, so no fans.

Robin.

1

Blecher_onthe_Hudson OP t1_j25wlg9 wrote

As I responded above I actually do have fans, the whole point of what I'm trying is to eliminate baseboards.

2