Need Advice on Plumbing Two Boilers

Good morning all,

I've been running the AA-130 for about 7 weeks now and all is working well with it. Now that it's gotten cold, though, I've concluded that I have a plumbing connection issue. My old oil boiler is still in place but the burner is disabled. I'm using the hot water coil in the oil boiler and the existing previously-existing thermostat controls.

The two boilers are kind of plumbed in parallel as shown in the attached diagram. The problem I'm having is that not enough hot water from the AA-130 is mixing with the oil boiler. The oil boiler water temp indicates about 30 to 35 degress lower than the AA-130. I'm running the AA at 190 just to keep the oil boiler at 160.

All if this is more noticeable since the temps here in central MA are running about 10F. I use setback thermostats but with the cold it takes too long to recover so I've disabled the setbacks.

I know I need to make significant changes in the spring, but I'm wondering if anyone has any ideas on any easy (less than 4 hour) fixes I can make to improve things?

Thanks,
Ed...

What size pipes run from the AHS to the oil boiler?

Looks like 1". The OD is 1 1/8", but I'm assuming the pipes measurements are ID.

There are several valves installed that I didn't identify. The attached diagram shows where two of them are. If I were to close those valves and installed the lines indicated in red, would that be effective? I'm looking to do something that doesn't require shutting down heat for more than a few hours.

Ed...

It looks like your circ is pumping in the wrong direction through the A-A if your drawing is accurate.

You have your system set up the same way I do with the following differences, I used 1-1/4" black iron pipe to connect the two boilers (as directed by Harman) and I have my circ. pumping in the opposite direction from yours.

The red line change that you show looks like it will elliminate the DHW circuit. You wouldn't want to do that.

What kind of circulator are you using?

JB and coaled,

Thanks for the comments. Pumps are Taco 007-F5.

I've actually got valves on both sides if the pump so flipping it shouldn't be a big deal. I'll give that a try.

Ed...

One inch should be large enough to do the job unless you're on full screech all the time.. I just wanted to make sure you didn't have 3/4". Can't hurt to turn the pump around. When we plumbed my buddy's AHS I phoned AHS & asked why they run it "backwards". The answer: "Becasue it works". Tryyy it.

So I flipped the pump around and it's really made no measureable difference. Thermostats have been screaming for heat continuously for at least two days now. I can't get the first floor to go above 71F. During the night it falls to 69F. An upstairs bedroom is hanging at 64F despite the thermostat being on for over two days now. Baseboards are warm but not hot. So it's like a trickle of heat from the baseboards is just enough to offset losses.

The baseboard return pipes on either side of the zone valves (on the return side) are pretty hot - too hot to hold on to. It seems like the only place pipes aren't hot is in the baseboards.

I've thought about putting another pump to push the water into the baseboard system.

Help! Any other thoughts on what I might try?

Ed...

Yup, , but more questions too. Before the coal, when you had just oil, did it work just fine?

My best guess is..... air in the pipes. After the AHS install, how did you purge the air from the pipes?

What kind of zone valves do you have?

Evening Freddie,

You bring up some points that I have hust begun wondering about myself. I moved into this house full time just less than two years ago. Last winter was my first entire winter here. Kept the heat down neer 67F or 68F cause I was using oil. I'm beginning to wonder if the basboard length is sufficient.

Three hours ago I opened all four zone valves. They're still open. Previously one zone was always off, another usually off. It seems to me that if I had a problem at the boilers, spreading the load across four zones rather than two or three should lead to the warm rooms cooling doen a bit. It didn't happen. Does my logic about opening all zone valves make sense? I have two zones upstairs - master bedroom plus the other bedrooms. Master has been on and only maintaining 64F. Since opening the zone valves the other bedrooms are now warmer than the master.

I just finished cleaning out the baseboard in the kitchen. Took the metal off, vacuumed it out, put everything pack together properly. When I had things opened up the pipe is too hot to touch for more than a second or two. Since its been cleaned and put back togteher, the air leaving the baseboard is at least 10F hotter than it was this morning 132 vs. max of 122.

I also noticed that in one of the rooms one of the baseboard pipes doesn't even have fins on a third of its length. (I've been telling my girlfriend that the guy who built this house is an a--hole. Maybe another thing to add to the list.)

So I'm beginning to think I've been hunting down the wrong problem. It's no more than 12F outside right now and since opening the zone valves the whole house has warmed up.

Zone valves are Taco 571-2. 24 volt devices.

So I'm still a bit confused but still chipping away it things. Gonna clean out more baseboards tomorrow.

Ed...

Ahhh HA! I've got you now, my pretty!

I think you're on the right track. Just for kicks, describe the master bedroom. Floor size, windows (how many, new, old, good bad), how thick are the walls, insulated? How high is the ceiling and how much insulation is in it? Does the room have one, two, or three walls exposed to the weather? Finally, how many feet of baseboard does it have?

One thing I've seen is people install new wall to wall carpet and block the bottom of the baseboard. My sister bought a house that wouldn't heat. She had two different heating companies try to figure out why it wouldn't heat. One turned up the aquastat, the other cleaned the boiler. Finally I drove the 260 miles to her place and cured it with a sheet rock knife in 5 minutes. No one noticed the carpet 3/4 blocked the baseboard!

I was told my first house was "built by a finish carpenter". It didn't take long before we realized he was probably from Finland and had a drinking problem.

Did you disconnect the #1 wire on the taco zone valves when you opened all 4 of them? You cannot leave them open manually without removing the power to the valve head or they may burn out. May be too late, but check them NOW!

Whistlenut - I was not aware of that. I left two of them open all night, reset them mid-morning. I think all is OK, but I'll need to confirm.

I've attached a diagram of the MBR suite. 19'x12' room with cathedral ceiling. 12 foot walls are exterior walls and cathedral gables exposed to unheated attic space. Two 30" wide double hung windows on one wall, one on the other. Insulation is typical - 3.5" in walls and at least 8' in ceilings. Cathedral gables ar at least 6", maybe 8". Baseboard on full length of both exterior walls.

Bathroom has only 4 feet os baseboard. Closet has 9 feet.

Diagram should explain all.

Ed...

If the baseboards in your bedroom were sized based on a 180F water temp. and you can't get the oil boiler over 160F, it makes sense that you are cold.

Slant/Fin has a free heat loss calculator that can determine what kind of baseboard lengths are required to maintain your desired temperature, you can get it here:
**Broken Link(s) Removed**