TT 170 problems recovering in high mass system

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  #1  
Old 01-13-12, 10:08 PM
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TT 170 problems recovering in high mass system

About 2 months ago we had our boilers swapped out. The old system was a gravity type using cast iron radiators with 2.5" piping and anchient oil burners. It's a 3 unit building and each unit had it's own dedicated boiler. Water temps were set at 205 degrees. I think each boiler was 110k to 125k btu but I'm not sure.

The installer I used replaced all three oil boilers with a single Triangle tube Solo and three circulator pumps for each floor/unit as its own zone. The rest of the piping and radiators were left in place.

The building is uninsulated with old windows. I'm sure the heat loss is horrendous, the installer was aware of this when designing the system. I was assured that an efficient boiler was better bang-for-the-buck than insulation improvements.

The boiler plumbing does NOT follow the Triangle Tube best practice of a primary/secondary pumping system. The returns from each zone flow right back to the boiler.

I'm running into a big problem because one of the 3 units is heated occasionally. It's typically left at 50 degrees 5 days per week. When we turn the thermostat up from 50 to 68 it can take as long as 8 hours for the demand to be met. The problem is that there's a huge mass of cast iron piping and water that needs to come up to temp. The return temps from this mass can be as low as 70 degrees. The Solo 170 has a 45 degree "safety" built in. (It will modulate down to only raise the water temp by 45 degrees above the input water temperature.

The system uses a Honeywell AQ251 series control configured to provide a 0-10v signal to the Solo. (ODR is handled by the Honeywell unit, not the boiler.) It eventually ramps up the target boiler temp to 190 degrees slowly over the course of two hours with a full 10v output to the boiler the entire time according to parameter "F" on the Solo. The Solo is constantly bumping into the 45 degree limit because the return temps are so low. We tried running the circulators faster but then the Solo can't keep up with demand from more than one zone simultaneously. As soon as the flow gets beyond 8 or 9 gals/min through the boiler the output temps drop off very quickly.

The in-room temps of the other two units actually go down while the boiler is trying to bring the temp up in the cold unit. The average water temp in the system apparently drops too much.

It took 3 hours to raise the thermostat by 8 degrees today. (at 30 degree outdoor temps.) A full 7 hours to get up to 67 degrees on the thermostat from 54.

Each zone uses a Grundfos Alpha in auto-dapt mode. Each pump typically moves 2 to 3 gallons per min. With all three zones demanding heat at the same time the boiler is lucky to put out 155 degree water, even if it's not being limited by the 45 degree safety.

Would I have this problem if the system was designed with a primary/secondary piping arrangement? Would that enable the boiler to put out hotter water so it's not limited by the 45 degree safety? I'm trying to figure out if the boiler is undersized or the piping is incorrect.

The boiler does maintain a very comfortable temperature after the system is fully heated. I have had to remove any setback schedules. It can't deal with recovering from setbacks. It would take 3 to 5 hours to recover from a 4 degree nighttime setback in the morning.

The installer did not do any heat loss calculations. He based the design on prior fuel usage in previous winters. (1800 gallons of heating oil for the whole building per winter.) He says he has been sizing systems like this for 20 years and never had a problem.

Any thoughts? I don't want to have to heat a unit full-time just to avoid discomfort in the other two units on the day the heat is turned up on the 3rd floor. As it stands this is one hugely expensive pain in my butt at the moment and now I'm forced to try to figure it out since my installer's solution is for me to install insulation.
 
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Old 01-14-12, 05:15 AM
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Well your installer seems to be a moron. Insulation would have been the most bang for your buck. then you move to getting new boilers. Of course he won't make money on insulations his advice is to install a boiler. The other problem is that your boiler may be properly sized, but when you do add insulation, it will become over sized. I do question his usage of the fuel usage for sizing. It's probably not terribly off, but a manual J would have been better. Given the availability of software for this, it is easy enough to do.

The drawback to a properly sized boiler is that it doesn't handle set backs well at all. Even with better insulation, a deep set back from 50 degrees is a problem. Adding the insulation will save you money and you can avoid such a deep set back if you do. The others will chime in about whether primary/secondary will help.
 
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Old 01-14-12, 06:42 AM
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I do live in Maine where the price difference between natural gas and heating oil is very significant. I think the bang-for-the-buck logic was based on continuing to use 3 oversized, ineffecient 50+ year-old oil boilers with $4/gal fuel. Fuel costs were estimated to go down from ~$7k/year to somewhere between $3k to $3.5k. As a landlord paying for heat that's a significant annual savings.

I do feel like the system we have wasn't designed for our building. I get the impression that it's one of those "this is the way we've been doing it forever and it works for everyone else" situations.

It appears the root cause of our problems is there's no way to regulate flow through the boiler. It can keep up with one zone pump without a problem, barely keep up with two and when all three are running it's putting out cold water.

The boiler also provides indirect DHW through a pump set in priority mode.
 
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Old 01-14-12, 07:49 AM
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I was assured that an efficient boiler was better bang-for-the-buck than insulation improvements.
EHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH... sorry, wrong answer!

Insulation is fuel you only pay for ONCE! It is ALWAYS the biggest bang for the buck, no argument.

Each pump typically moves 2 to 3 gallons per min.
How do you know this?

solution is for me to install insulation.
Should have been done first.

when all three are running it's putting out cold water.
Yeah... too much flow through the boiler.

I'm sure it should have been piped with the P/S...

Can you provide photos of the install?
 
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Old 01-14-12, 08:04 AM
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I'll snap a few photos and post them shortly.

I'm getting the GPM numbers from the digital display on the Grundfos pumps.
 
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Old 01-14-12, 08:13 AM
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Each zone uses a Grundfos Alpha in auto-dapt mode. Each pump typically moves 2 to 3 gallons per min. With all three zones demanding heat at the same time the boiler is lucky to put out 155 degree water, even if it's not being limited by the 45 degree safety.
Wondering why the pumps are moving so little water? That's like as slow as they go, isn't it?

I have to admit that I know very little about the Alpha, and how it makes it's decisions ...

Even if all three pumps were on and at 3 GPM, you would think a 170K boiler should be able to keep up...

You know you need to post the pics to an off-site photo host, like a FREE account at Image hosting, free photo sharing & video sharing at Photobucket and provide a link to your PUBLIC album here for us to visit and view, right?
 
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Old 01-14-12, 08:22 AM
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I have a web server I can post them on. I'm installing some photoshop updates at the moment so I can resize the photos for web use.

FWIW, the boiler is rated at 170 input. I think it's about 157k btu output. Yes I think it should keep up.

The local gas utility replaced our meter when they relined the feed from the street. The boiler was not tested after the meter was changed. The installer didn't think this would be an issue since the flame is burning blue as viewed through the inspection plate.
 
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Old 01-14-12, 08:25 AM
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Don't make them too small! We're old dudes with bad eyes... we like to see detail!
 
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Old 01-14-12, 08:34 AM
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The boiler was not tested after the meter was changed. The installer didn't think this would be an issue since the flame is burning blue as viewed through the inspection plate.
Ohhhh... I get it... the flames are blue so everything is OK ... what a crock.

I don't SMELL any CO, it's OK.

Yeah, I can tell the gas pressure is OK too... just by looking at the flame... NOT!
 
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Old 01-14-12, 09:00 AM
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Well, switching to gas vs. oil will save you money for sure. I think the per BTU cost difference is at least 30% at today's prices. Depending on what you do, insulation isn't very costly considering the savings. I wish I insulated first before getting my boiler.
 
  #11  
Old 01-14-12, 09:17 AM
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Add Insulation. You may have to keep the un-rented unit warmer until then. Don't do night setback

New gas lines, verify size & flow, use a water manometer, test with unit off and at high fire. Spec is in Installation manual, somewhere around 3.5" WC (water column)

I have a TT Solo 60 in my house. Your heat gain rate is better than mine (1.5hrs for 1*F) Temp. is limited by ODR.

Get combustion checked, I bought a tester & found that mine was close from factory. It has a single gas throttle screw, easy to adjust.

You might get P/S to run at a higher boiler temperature. This would be with higher boiler flow vs. system flow, where some of boiler flow goes the wrong way at the close T's & recirculate through boiler. Usually not done, on purpose.

I just refered to the TT 175 Pressure Loss chart, minimum flow should not go below 8gpm. A Taco 0010 would flow right at 25gpm. This pump has a flat pump curve, lots of flow with a lower head. I just Speced the Delta-T version of this pump in a design I'm doing with zone valves.

Set the Alphas on High. Check flow rates again, make sure flow is not restricted, say by air eliminator etc. etc. These are very energy efficient ECM pumps, but not really high head.

http://s3.pexsupply.com/manuals/1252..._PROD_FILE.pdf
 

Last edited by Buffalobillpatr; 01-14-12 at 10:22 AM.
  #12  
Old 01-14-12, 10:41 AM
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No flow or head loss calculations were performed as far as I know. The radiators weren't even measured. The assumption is that it was a gravity type hot water system so head losses should be minimal. ( It's a 3 story building.)

The installers originally left all three Alpha zone pumps at the highest speed setting. The digital readout on the pumps would vary between 6 and 8 GPM. The house would not heat up if there was more than one zone of demand.

Working on the photos now. Just had to make an emergency veterinary run for the dog.
 
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Old 01-14-12, 11:21 AM
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Here's the photos of the system.







Much higher resolution versions available at:
http://www.rufusthedoofus.com/boiler1.jpg

http://www.rufusthedoofus.com/boiler2.jpg

http://www.rufusthedoofus.com/boiler3.jpg
 
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Old 01-14-12, 12:33 PM
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Looks WAY better than most. Pumping away from expansion tankS and air elemonator as it should. It could be converted to P/S without making it ugly.
 
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Old 01-14-12, 12:39 PM
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BTW, there was never really a choice to be made between insulation or a boiler. The decision was to do one boiler or all three at the same time. All three of old oil boilers were commonly vented up a single flue of the chimney. That's not allowed by code any longer. One of the three was in need of replacement. State law says that you can't install a new boiler without it's own dedicated exhaust. Most people opt for a direct-vent natural gas fired boiler to make retrofits easier in these instances. The installer convinced us to remove all three units at the same time to save on fuel bills and equipment costs instead of replacing them as needed when they eventually failed.
 
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Old 01-14-12, 12:42 PM
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I figure the P/S pumping circuit could be added vertically to the right of the boiler.
 
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Old 01-14-12, 01:10 PM
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Simply converting to Primary/Secondary, is not going to keep the 1st and 2nd floor's warm, durring 3rd floor recovery.
The most it would do is allow the boiler to stay at max fire, when the differential exceeds 42 degress, under low flow conditions.

In the bigger picture, the lower the return temperatures that can be made to work, the greater the efficency will be.

There are Tekmar controls that can do prioritized load shedding, when supply temps drop below a set level.
Something like this could work when the 1st or 2nd floors call and the temp drops, then the third floor load would be shedded.
I do knot know all the in's and out's of that Honeywell control.
But maybe it has a similar capability, or it can be addded on somehow.



Peter
 
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Old 01-14-12, 01:15 PM
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"stay at max fire" is what Rufus wants.


This would be the ticket

0010-VDTF3 - Taco 0010-VDTF3 - 0010 Cast Iron Variable Speed, Delta T Circulator, 1/8 HP
 
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Old 01-14-12, 01:36 PM
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I believe it only modulates down. to protect itself, when there is not enough flow.

Where would a Delta T circulator be put in that system?
How is going to help?

157,000 btu/hr is only going to raise 8 GPM water 40 degrees, at best.
Say 78 to 118. If 118 degree water at 2.66 gpm for each of the other two floor, can not keep them warm, then the only solution is to throttle the output into the third floor somehow.

Peter
 
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Old 01-14-12, 02:07 PM
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So what is the story on that 3rd unit with the deep set back? Maybe we can come up with a temporary solution until you can get the insulation squared away. I think you should do a heat loss calculation on the building to make sure your boiler isn't undersized. What are your outdoor temps right now?
 
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Old 01-14-12, 02:30 PM
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For the Boiler pump if he switches to P/S, but after thinking about this a Delta-T there might have a conflict with the boilers control, they might chase each other up & down.
 
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Old 01-14-12, 04:06 PM
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The 3rd floor unit is unoccupied and being renovated. I live 100 miles from the rental building and am typically down there on Friday afternoon thru Saturday or Sunday evening. I was manually setting back the thremostat when unoccupied thinking I would save on fuel bills. This weekend I only set it back to 62 before I left.

The Honeywell control is a very simple unit. I'm not impressed with it. (I have Tekmar stuff at home for my radiant system. I love the Tekmar controls.)

The design problem I'm trying to rectify is the Honeywell controller is demanding XXX degree water based on it's ODR curve and the boiler isn't able to satisfy the demand if more than one zone pump is running. (This is even after the 3rd floor has completely recovered.) I've manually configured the boiler to run all the way up to 194 degrees which is its upper limit. It will never hit that temperature with more than one zone pump running. Maybe I am wrong but I view this as a problem. The boiler is either too small or the design is wrong for the building.

I don't know yet if the boiler isn't running at max output or if I'm dealing with a design problem. There are combustion test results taped to the side of the boiler from when it was first commissioned. I didn't verify them against the specs in the manual.
 
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Old 01-14-12, 04:10 PM
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What are your outdoor temps right now?
Mid teens. Possibly single digits tonight.
 
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Old 01-14-12, 04:14 PM
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I believe it only modulates down. to protect itself, when there is not enough flow.
That's what the installer thought too. I was standing next to him when he was on the floor with the Triangle Tube rep and learned there's a 45 degree safety. It's internal MCBA logic will only allow a max delta T of 45 degrees through the boiler. I've read that the goal for this boiler is to maintain a 30 degree delta T for maximum efficiency.
 
  #26  
Old 01-14-12, 04:26 PM
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Get yourself one of those salamander heaters for the apartment you are renovating. When you show up, kick it on to boost the heat and then cut it off when it reaches temperature. Then the boiler can maintain it.

How are you making hot water?
 
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Old 01-14-12, 04:30 PM
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Hello Rufus T.,

If you are there tonight, it would be interesting to hang out down by the boiler for the late evening. Or early tomorrow morning.
See if the boiler is at 100% the whole time?
See if the zones are running constantly or if they satisfy and shut off. etc.
Just because the water won't get to 194 doesn't mean the boiler is too small, as long as the zones heat ok.

Is there any way to verify if the boiler i actually firing 100%, from the control panel?

Peter
 
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Old 01-14-12, 05:05 PM
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"Is there any way to verify if the boiler i actually firing 100%, from the control panel?"

Yes, in a round-about way. You have to enter the MCBA access code, pg 52 in my manual.
Then step to the fan display, mine reads 5340 rpm at it's max output, not sure what it is on a 175 at your altitude.

If you have an indirect hooked up, it should go to max rpm heating DHW, record it.

If you decide to go P/S I would recommend the standard Taco 0010, with your isolation valves use a good 1-1/4" Globe valve on the pumps output side. That way you can adjust the flow through the boiler. This pump handles this throttling just fine with its flat curve.
 
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Old 01-14-12, 05:18 PM
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Is there any way to verify if the boiler i actually firing 100%, from the control panel?
I have checked 2 things to see if the boiler is at max-fire. You can force it into max-fire by pressing two keys on the front panel for a few seconds. This will force max-fire for up to 10 minutes. I also checked status code "F" to verify that the Honeywell is indeed putting out a full 10 volts on the 0 to 10 input. 10 volts indicates max-fire.

I have no way to tell if the boiler is actually putting out the BTUs it is supposed to. The installer manual describes a process where the boiler is placed in max-fire and the gas meter is watched for a certain amount of gas usage in that amount of time. Then there's some math to figure out how much input gas vs. time to determine if the boiler is actually putting out what it's rated at. I seriously doubt that this procedure was followed when the boiler was commissioned. I think they just did a combustion test and printed out the results.

I have no idea if a change in gas meter would matter to the boiler. A larger capacity meter was installed when the gas co. sleeved a new plastic line into the house from the main under the street. They are prepping our neighborhood to transition from a low pressure distribution network to a higher pressure network. At least that's what I was told as the reason for them to need to swap my meter.
 
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Old 01-14-12, 05:30 PM
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I forgot to address this part. I'm not at the building tonight so I can't check the exact numbers.

See if the boiler is at 100% the whole time?
See if the zones are running constantly or if they satisfy and shut off. etc.
The zones will satisfy and shut off from time to time. At least that was the case this afternoon when it was 27 degrees outside and quite sunny. The boiler is always at 100% if there's more than one zone demanding heat. If all three zones are on simultaneously the boiler won't put out more than 155 degree water with the zone pumps in auto-dapt mode.

I don't know the difference in BTU output from cast iron radiators with 150 degree water vs. 180 but I can tell you that the tenants on the first and second floor start complaining right away. That's really the worst part about this problem. I have instructed them to leave their thermostats at 70 degrees and essentially "deal" with the drops to 67 that happen randomly over the course of the day. I assume these correlate to periods of DHW demand. (Five people living in the house.)
 
  #31  
Old 01-14-12, 05:59 PM
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I'm afraid you might not have enough boiler.
Tonight and tomorrow night will be a pretty good test.
Although no where near 10-20 below than i'm guessing can easily happen.
I'm also guessing the location is somehwere near Portland?

If you don't have enough boiler. Then it would probably be best to leave the third floor set at 50 degress, to free up some btu.s.
While you can get together with the installer and figure out what to do.
Add a second boiler, maybe.



Peter
 
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Old 01-14-12, 06:07 PM
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Yes, Portland.

While you can get together with the installer and figure out what to do.
I got together with the installer on Friday afternoon. He's aware of the problems and did not have a solution or even the hint of a solution when he left on Friday. Hence my need to find somewhere to bounce ideas around. At the moment I'm $21k into this system and I feel like I've been screwed from behind with 60 grit sandpaper condoms.

I'm considering contacting one of the top hydronic design companies in Maine. But that costs money. And my installer is also a customer of theirs. I'd rather not ruffle too many feathers if I don't have to. I really need a professional to step up and tell me what's wrong with my system. That's going to cost me a few bucks. I'm hopeful that I don't need to get to that point because that means I'll be seeking additional damages in the lawsuit that will ultimately follow.
 
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Old 01-14-12, 07:20 PM
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Personally i'm totally against any sort of enrichment for lawyers.
Loose loose.

Sit down and work it out.
Sounds like too much $$, by double, but i'm guessing that includes chimney work and other odds and ends. So maybe too much by a third. Depending all the hidden gotcha's.

Worrying about ruffled feathers and a lawsuit in the same breath. hmmmm.
If you guy is "also a customer" then he certainly forgot to call them for your job.


In any case

Northeast Raidant Tec.
The Radiant Design Specialists | Northeast Radiant Technology, L.L.C.

IMO these guys are top shelf.
Check it out.

Peter
 
  #34  
Old 01-14-12, 09:06 PM
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Rob Brown is the person I was planning to call. NRT is a great outfit. Rob designed my radiant system here at my home 100 miles north of Portland. NRT also designed my neighbor's off-grid radiant system and a number of other homes in the area. I did all of the install work except for the boiler. I'm almost 99% sure NRT wasn't involved in designing the system for my rental building. They would have started with a heat loss analysis and worked from there.

A lawsuit is a last resort. Unfortunately this problem has been ongoing for 4 weeks and it's not anywhere close to being resolved.
 
  #35  
Old 01-15-12, 04:07 AM
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Agree NRT would be a good third party for this.

I don't see anything substantially wrong with the installation. All the mistakes a knucklehead would typically make are missing. A knucklehead, for example, would not have sized the expansion tanks correctly (these appear to be plenty). A knucklehead would have used 3/4" piping everywhere. (This appears to be 1"). A knucklehead would not have done such a nice job on the layout and had 6-8 straight pipe diameters into and out of the pumps, good valving for maintenance, etc.

Except I for one would never put electronic controls underneath all that piping and valving....

Except for paying more attention to the load dynamics of a multi-unit building.

And except for the boiler sizing. If it wasn't based on a heat loss, how in the world can the installer simply pick a 170 for this.

How many square feet is the building? As others have pointed out, the insulation should have been addressed before doing the boiler. But especially with a modcon, it's never to late to insulate and air seal. With a good blower door and IR study, it might even be possible to identify some smoking guns in the building envelope that can reduce the heat loss down to the range of the boiler, if undersizing is in fact the problem.

I too far prefer tekmar to the Honeywell, but what little I know about the AQ series suggests it ought to be ok for this application.

Like Peter said, simply converting to p/s does not necessarily fix this problem unless there's something weird with the flow rates. The minimum flow rate for the 170 at full fire is 8 gpm. The three Alphas should not be able to push the boiler over the limit to keep a decent dT. You might try setting the Alphas on medium fixed speed. I would not use autoadapt in this setting, with the variable load of different units and an independent ODR. (I have a pair of Alphas and really like them, although I mostly only wanted them for the electrical savings and to sit on low fixed -- it's a constant circulation system that runs great at 1 gpm.)

It would be good to see some pics of how all that PEX connects to the old gravity piping.
 

Last edited by xiphias; 01-15-12 at 05:52 AM.
  #36  
Old 01-15-12, 05:28 AM
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I don't know the difference in BTU output from cast iron radiators with 150 degree water vs. 180
Use the top part of this chart for BTU output per sq ft EDR: btu_pipe

Another one here: Radiator Sizing Guide
 
  #37  
Old 01-15-12, 06:19 AM
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I don't see anything substantially wrong with the installation. All the mistakes a knucklehead would typically make are missing. A knucklehead, for example, would not have sized the expansion tanks correctly (these appear to be plenty).
They came back 3 times fixing this issue.

Except I for one would never put electronic controls underneath all that piping and valving....
One of the pex to copper crimps started leaking onto the Honeywell about a week ago. Luckily the tenant on the 1st floor noticed it at placed a cup there to catch the drips.

And except for the boiler sizing. If it wasn't based on a heat loss, how in the world can the installer simply pick a 170 for this.
The calculation was based on prior year's fuel usage. A baseline of 1800 gals of oil was the starting point for the calculations. Then he did some btu/sq.ft calcs to see if 1800 was a reasonable amount of heat for the size of the space and the type of building. The installer has put this boiler into two homes next door to ours. One of the homes is super insulated, the other is uninsulated like ours.

I do plan to do insulation. It's just can be quite disruptive with tenants in the building.
 
  #38  
Old 01-15-12, 07:08 AM
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OK, so maybe some knuckles here....

Air seal before insulating.

Starter guide here:
http://www.energystar.gov/ia/partner...e_May_2008.pdf

Also check out "Insulate and Weatherize" in the Taunton Press series.

How many sq ft building? 1800 gal is probably around 1.6 million BTU assuming 65% efficiency for old boilers.

How many degree days in your climate? What is the outdoor design temp?

How many radiators? Figuring the sq ft EDR would be a ballpark first step at seeing at least what the theoretical upper end output of the radiation would be.
 
  #39  
Old 01-15-12, 07:53 AM
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How many sq ft building?
1850 sq/ft per floor of living space. Unheated basement of the same size. Unheated attic space above the 3rd floor too.

The first floor has 9 radiators of differing sizes. The 2nd and 3rd floor each have 8 radiators. The third floor has all new energy efficient Pella windows. Some of the windows on the second floor have been replaced with double pane vinyl. The ones that haven't been replaced are the original single pane windows from the late 1800s with storm windows over them. There's no insulation anywhere in the building.

Thanks for the Air Sealing guide. I think I'll need to address some of those issues ASAP.
 
  #40  
Old 01-15-12, 07:57 AM
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Join Date: Jan 2012
Location: usa
Posts: 33
How many degree days in your climate? What is the outdoor design temp?
Charts claim outdoor design temp for our area should be -1 degrees F. It hit that temperature last night.
 
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