Steam boiler with loop for baseboard heating is making the house way too hot.

skang

I just moved into an old house heated by gas fired steam heat. Just got a new boiler after my old one was found to be cracked. Sad because this is our first month in the house. All of this is new to me, so I'm a major newb. There is an extension to the house that is heated with baseboards fed through a hot water loop from the boiler. There are two thermostats on the first floor, one for the steam heat which heats the 3 main floors, and 1 for the baseboards in the expansion. After the new boiler, the steam heat section warms up great. The problem is when I try to heat the expansion. I set it to 70, it never quite gets there and it causes the boiler to run continuously, heating up the rest of the house to 80+, even though i have the steam section set to 65.

What is going on? Any expertise would be appreciated.

Photos of my setup

Jamie Hall

There should be an aquastat on the hot water loop, or on the boiler itself. This should keep the boiler water in some sort of reasonable range -- say 160 to 180 -- to keep the water hot, but not boiling, for the hot water loop. Then if the main house thermostat calls for heat, that would override the aquastat and bring the boiler up to steaming -- and then when the main house thermostat stops the call, the control would revert to the aquastat.

Odds are that when the new boiler was installed, either the aquastat was not installed or was miswired.

You can do a quick check on this yourself. Turn both thermostats way down. The boiler should be off. Now turn the main thermostat up. The boiler should come on; let it get to the point where the radiators are heating up. Now turn that thermostat way down again. The boiler should turn off. Now turn the hot water loop thermostat up. It's circulator pump should run, and the hot water radiators should get warm -- but the boiler should not run, at least for a while -- perhaps as much as 15 to 20 minutes.

neilc

sounds like you're miswired with the aquastat and Ptrol in parallel and you are controlling by Ptrol when just calling for the HW loop.
Someone needs to check all those control wires.

Also, your Ptrol looks to be set a little high, between 1 and 2 (?)
dial that down to 0.5 as you don't want or need that high a steam pressure.
there's also a wheel inside, check that it's set to 1.
The pressure setting adjustment won't help with the HW and steam overheating issue, but is worth doing just the same as steam likes low pressure.

skang

Thanks, testing now and will update with results. I have a photo of the aquastat in my photo collection above. Looks to be set around 145.

skang

Thanks neilc, i pushed those values up thinking it might help my hot water issue (like i said, newb). Will bring those values back down.

skang

Ok so testing complete.

Main thermostat, and HW thermostate set to 55 = boiler off and cooling.

Main set to 80, HW set to 55 = boiler firing and radiators heat up, beautiful. Was having issues before the new boiler.

Main set to 55, HW set to 80 = boiler and circulator both fire up.

I can call up the hvac guys, but perhaps its something i can fix?

neilc

Wires can be hard to do over the internet,
are you meter handy?
or,
Try calling your contractor back out,
explain this situation,
show them this thread,
they should make good on what seems to be their wiring mistake.

If you're not confident in them,
https://heatinghelp.com/find-a-contractor/
where are you located?

skang

Yeah I'm ok with a meter. Just watched this video: https://www.youtube.com/watch?v=BZJ2tch3_oc

I'll update with what I find.

skang

Ok so the inside of my aquastat looks nothing like that video. Its just the temperature dial and a single wire going into the green Taco box. I'm also second guessing my statement that the circulator fired. It might just be the boiler. The thermostats seemed to get wired into the back. Here's a picture:

Wiring behind the boiler

neilc

Caution, 120 Volt

pop the cover on the taco and take a picture closeup showing all the wire terminations,
and a larger one showing the wires coming in, from where,

I don't think I see the thermostat coming to the taco,
which means they paralleled the HW with the steam.

there are other ways this could be wired,
but here's taco,
https://www.taco-hvac.com/uploads/FileLibrary/102-169.pdf

also post the mod # of the aquastat,
and a pic of the wires landed inside,

Jamie Hall

The thermostat for the hot water heat should not come anywhere near the boiler controls. It should control only the circulator -- nothing else.

skang

Here are some pics of the taco and the wiring on the other side. The only thing going into the taco is the wiring for the aquastat.

https://photos.app.goo.gl/umX7EypEYad2m1q99

skang

...and the aquastat is a honeywell l4006a.

Jamie Hall

You need to completely rethink the wiring on your system. The thermostat for the steam should control the boiler, along with the various safeties. The thermostat for the hot water should control the circulator pump, and nothing else. The aquastat for the hot water should also control the boiler, like the thermostat for steam, so it can keep the boiler warm enough for the hot water heat system when steam is not being called for.

skang

So I did a bit more digging, and it seemed strange that even though I have two thermostats, it looked like only one was going into my system. I traced it out and it seems they have both thermostats tied together.

Not sure if that makes it easier or harder for me.

https://photos.app.goo.gl/W9Ybh6GdC2cufBVu6

Jamie Hall

They may well have tied both thermostats together -- which is just plain wrong. See my comment immediately above as to what should control what.

skang

Just to close the loop, contractor is here today to do exactly as advised. HW thermostat is getting wired up to the relay, aquastat is getting wired up, through the relay to control the boiler. Steam thermostat separated out and controlling the boiler.

Thanks again for all the help.