Not Sure My Installer Did This Right

ColdAlbertan

Hi everyone. I was researching my issue and chanced upon this forum. While my specific question wasn't answered, I noticed that there were definitely people active here who could help me. 

I've brought up various issues with an installer, who was recommended by a friend, and he gets defensive and seems to be guessing as to the solutions to my problems. For example, I had to argue with him multiple times about how a radiator he installed was not the right BTUs, and was in fact a third of the target. It was so egregiously wrong that it made me question whether he actually knew what he was talking about. He was very dismissive. I might not be a plumber, but I can do math and eventually he clued in. This post isn't about him, but I just need more opinions about this system because I can't rely on him to figure it out. I would really appreciate your input.

Thanks in advance,
Stewart



This is a UFT-175 with three zones and a hot water tank. One zone is about 30' of baseboard heat. Another is, without measuring it, a 40" x 24" European style radiator, and the third zone heats forced air via a water heat exchanger and blower.

I have been losing about 2 gallons of water from the system per year since installed two years ago. One source I identified was a connection to a radiator, which was fixed last summer. The other is this pressure release on the CH return line. 



In order to prevent Er:16 supply line overheat codes, I have the system turned down really far. The maximum supply temp (6:cH) is set to 170°, and the heating capacity (18:db) is set at 50%. Without doing this, the system will get so overheated that it will shut down completely. The installer's only solution was to crank up the circulators and the fan speed on the hydronic exchanger. 

So I have a few questions. 

1. Why, why, why, why, why!? 
2. According to the manual on table 11, CH piping size should be 1.25". Does this refer only to the lines between the pumps and the boiler, or also the supply lines? I ask because the supply lines are all 3/4".

3. The pumps pump towards the boiler. Is this an issue? 



4. Related to question 3. There appears to be some back flow into zone 2 when zone 3 is on. Is this a big deal? 

GroundUp

There is a lot of yuck there. Both the baseboard zone and the radiator zone are too small for the minimum boiler firing rate (not sure about the 3rd without more information). Also there is no primary/secondary piping which may be hindering boiler flow and causing the overheating. This system was poorly executed and the boiler is much larger than it needs to be. The right way to fix it would be to start over, but at minimum there needs to be more load on the smaller zones if you want to keep that boiler.

JohnNY

The manual shows primary-secondary piping as optional, even with multiple small zones. The guy did a great job soldering and supporting his piping. I'm not sure I hate this installation, the pumps should pump toward the boiler in this case and I'm definitely not concerned about the ¾" zone piping.

hot_rod

A heat load calc is always the best first step, room by room. Everything in the system sizes to that. I'm guessing with the little info you have a 50,000 or lower load? Us the free www.SlantFin.com load calc to do your own calculation.

While some of the new mod cons can be direct piped, they do need a minimum flow. Could be with one zone alone calling you do not meet that requirement, that can cause high limit block outs. The manual should indicate flow required. Of course each circulator needs to be able to meet that min. flow, consider what they are connected to.

Once you have the BTU/ hr. load number, crank the limiting function down to that, how low does it allow, 30%? Some boiler controls have a ramp delay function which allows the boiler to slowly step up to the load, very useful with multi-zoned systems like yours.

Could be with those vents on S&R above the boiler and pumping into it, you may pull air into the system. I'd turn the caps down on both high point float vents. Maybe replace the leaking one A check valve or small ball valve below the vents allows for easy service, if you keep them. They help on first fill, after that the air purger should get you to a quiet, air-free condition.

You want to run the system as low as possible temperature wise.

After you do a load calc, see how the three emitters match that load and at what temperatures. Limit the boiler to that SWT, enable outdoor reset. The lower the SWT, the better the efficiency.

Download this free journal to see how to derate output on the 3 different emitters you have.

hot_rod

Looks like 2.5 gpm min. on your model. And it does have step firing, use it!

Zman

1. The zone piping is OK at 3/4"
   
2. Technically it does not need to be piped primary/secondary as long as minimum flows are maintained. Judging by the symptoms you describe it sounds like that is not happening.
   
3. The zone circs (and DHW circ) should have check valves to prevent the reverse flow you are experiencing. This may also be contributing to the flow issues at the boiler as some of the water moved by the zone circs is not going through the boiler.
   
4. The circs, as installed are pumping into rather than away from the expansion tank which is not a good practice.
   
5. The leak in the air vent is an easy fix, just swap it out for a new one.
   

In other news:

• The boiler is very likely grossly oversized.
  
• The "fan in a can" for combustion air is really odd when the boiler is intended to be sealed combustion pulling air from the outside. How is it controlled?
  

My suggestion would be to install checks on the circs (Taco may make an IFC that would snap into the circ) and see if the flow problems still persist.

Unless you have a copy of the combustion analysis performed when this was set up, I would suggest having one performed to be sure the boiler is running correctly.

ColdAlbertan

Wow. Everyone, there is a lot to go through here. I commented on how the boiler was oversized and the plumber said that he did so in case we decided to heat the garage, or an outdoor hot tub in the future, which we had talked about. But I think you hit the nail on the head with it being to big. 

On that topic, it isn't that the house is too small (1150 square feet) it is that the actual radiators don't create enough load? I could in theory add to the zone that goes to the European style radiator by supplementing the heat in an upstairs bedroom that gets forced air through poor ducting and is always cold. I could also heat the garage off that line. 

@Hotrod, I have used step firing before and didn't really understand what it was doing, so I turned it back off. I will turn it back on due to your recommendations. 

I'm not sure I understand how to achieve a specific minimum flow rate. Is there a specific setting on the TACO pumps to ensure I'm meeting those rates?

@Zman, the cold air intake seems pretty common for around here and is the exact same idea as was in my last house for a forced air furnace. The boiler pulls air from the room and air passively enters the room from outside through the pipe in a can. So, are you saying that the unit might be designed to be directly piped to the outdoors?

Just to be clear, I gather from what several of you said, that the leaky part could be either defective, or operating normally and venting air that entered the system somehow?
The radiators work quite silently and I don't think there's much air

EDIT: either way, I learned something. I thought that it was letting off steam from when it got overheated in the boiler, and that there might be back flow up from the boiler. 

Thank you all for your knowledgeable responses. 

ColdAlbertan

Correction on the radiator. It's 48" x 24" and double walled. I can't seem to find the email with the specs in it. It certainly heats the room, but it does run more than all the other zones. The room is about 15'x20', there's no windows, but a 6' sliding (glass) patio door, and a stairwell going up. I suspect it runs a lot because the air flows up the stairwell, not because it's too small. 

hot_rod

Look up the spec on that panel rad, see if it can flow 2.5 gpm, and what pump head it requires. Of your 3 types of heat emitters, I suspect the panel rad may be restricting flow thru the boiler and causing the quick increase and over-heating.

To know the flow rate you can use a flow meter, or calculate it with the piping and radiator info.

If the boiler races to high temperature with just the panel rad running, there is the flow restriction.

The ramp is just as you imagine, it keeps it at low fire for the time you select then steps up slowly. It may be enough change to keep from hitting limit.

I'd still do the room by room load calc for your own piece of mind.

Loos like a Dianorm radiator, here is a typical spec. It's possible you are only moving 1 gpm through it, far less than what the boiler wants.

That system cries out for a single delta P circ with zone valves. A hydro sep would be a nice piping to assure boiler flow regardless of distribution requirements.

What you have may be salvageable, one step at a time.

GroundUp

Regardless of flow rate, that boiler can only fire down to 17,500 BTU. The panel rad nor the baseboard zone is putting out that many BTU unless it's firing at 180+ degrees at all times. This causes short cycling, and the response time in the UFT control is rather slow which is creating the overheating you're seeing. I used to install UFT exclusively and came across this very issue many times. 20 GPM isn't going to make it overheat any less if the emitter output is still less than minimum firing rate.

mattmia2

their workmanship is pretty good. too bad they didn't do any math. i see a buffer tank in your future.

mattmia2

How ar the circulators wired, is it set up so the boiler only fires when the circulators are running? How does it pick the 3 dh circulators, is there a zone control panel?

At 175,000 btu/hr the min firing rate is going to be about 15,000 btu. The return water on that panel rad or the baseboard may be so high that it is causing lockout. Lowering the max water temp might help and you likely don't need 170 for adequate heat.

if you have the outdoor reset set properly to meet the heat loss of the house and the emitters sized right technically the boiler should run continuously at a low rate. i'm pretty sure in your case other than on the coldest days the minimum firing rate is more than the heat loss of your house.

other things i would adjust is i would set the anti short cycle timer to 15 or 20 minutes as well as set the delta t to 15 or 20 degrees on the domestic heat. there are anti short cycling features in this boiler. also you can turn the max rate for dh way down but keep dhw higher assuming it is making separate dh and dhw calls to the boiler itself.

and that is clearly set up to take combustion air from outside, no need for the fan in the can unless you have other fuel burning appliances.