More winter, more problems :(

giantsean

Hi All,

Sorry to bring up the exact same conversation every single winter, but I am having some problems getting my downstairs warm now that the weather has turned. It appears that about 20 degrees outside temp and I start to have problems. Add wind and it's worse.

I have a Navien CH-240 feeding a TAM7 air handler w/ a 42K BTU (noted, ideal conditions) hydro coil, which is dedicated to the 1st floor and split into two zones. The maximum distance from the AH to the farthest register is about 50ft. I have done a LOT of work buttoning up the downstairs - replaced windows, applied insulation where there was none, air sealed, but I just cannot get the 1st floor past 63-65 on a cold day. I have tried tuning the TAM for maximum airflow, but it almost seems like the problem is that it is lukewarm air by the time it comes out of the registers. It makes me wonder if heat is actually being removed from this coil or whether there is some weird ducting problem elsewhere. I did change out the filter today and even set the fan to the highest CFM setting to try to get some velocity.

I also tried upping the supply temp on the Navien to 180. Just as last year, I can get it to peak in the high 170's for maybe a few seconds but it kicks off fast and throttles back to the 160 area. Some have told me it is because return temp is too high. I have unplugged the ODR and left the remote to try to dial in the supply temp, but it still seems to do whatever it wants.

At this point I almost don't even know where to begin. I really don't understand why it's so difficult to get this place warm!

Thank you for any advice

kcopp

Why don't you add a zone of high output baseboard to kick on when it gets cold.

giantsean

My wife likes the clean wall look... this is why we scrapped the rads when we renovated (for the record, NOT my idea!)

Brewbeer

Can you put in a larger coil in the air handler?

njtommy

Check your dip switch settings

njtommy

Also which model number coil do you have? Does it go on top the unit or slide into the unit.

kcopp

So I guess it comes down to clean look or being warm. Panel rads look pretty clean.

http://www.qhtinc.com/radiators/

giantsean

Well slightly better news that the rooms were able to hold more than 60 all night. This though at the expense of running full cycle all night. One thing I didn't mention is the house is still being actively renovated and I was able to find a couple of returns which were blocked, which seemed to help a little but not enough.

The coil (BAYWAAA05SC1AA) is a slide in which is "the one that fits" for this model of 2 ton TAM7 (TAM7A0A24H21SDB) matched to a 2 ton condenser. It is supposedly good for 42K BTU under ideal conditions

@ njtommy - thanks for that find! I have been trying to pick out relevant info from the Navien books but they are so poorly put together I'm amazed anyone can find anything in there

@ kcopp - singing to the choir there We had cast iron rads in some of the rooms and I cried a little when we removed them (and not because they were heavy!) Luckily I did keep em so you never know, they may make a triumphant return. My first question is how a new state of the art system installed by professionals could suck so bad. I am not through looking for a sweet spot yet and if I truly can't find one I'll start looking at Plan B

So my open questions now:

- I have the 3m "orange" filters in there now - would going to a lower restriction filter (like that green fiberglass) make a significant improveent?
- Is it worth trying to blow out the heating coil to remove any built up dust? If so would it need to be removed first?
- The installers piped the coil backwards (inlet is going into the outlet) but most tell me it makes no difference. I know Trane thinks there is a difference, but if it's not much it may not be worth draining and pulling the whole thing apart first. However I'll do it in a second if it is
- Some of the registers are 50+ feet away from the handler and take several bends, and understandably there is not much wind there. Is there any way to improve that? Would a 2nd AH be out of the question to serve that side of the house?

Thanks again!

njtommy

Your duct work and air flow could be part of the problem. Yes you coil is 50,000btus but you only have 800 cfm to play with.

More CFM equals more btus. Even tho it may lower your supply air temp a bit. Do you have a thermometer to give us a supply air temp?

njtommy

@kcopp Those panel rads look really nice as most do.

giantsean

Well we are making some progress. I hit DIP 8 on the navien and set to max 185. For the first time ever it is staying steady in the 175-183 area! Return temp from the boiler reading is from 143-150.

The other interesting thing is that it appears to not be cycling as much...perhaps as the high return temp setting prevents it kicking off. I'm thinking that can only be a good thing.

I grabbed the only thermometer I had handy and threw it into the liner of the register in the most troublesome temperature room and after about 30 mins it was reading 89, so it does seem to have helped.

Finally I set the hydro control board to external coil mode which I already believe overrides all handler fan settings and pins it on a high speed. I just don't know how high.

Note this is all with only 1 zone calling. I imagine pressure will reduce when the other zzoneibe opens, just not able to test now as there is drywall sanding going on.

Thanks for the help so far... Getting closer!

njtommy

If you can get your supply air temp up to 100-105 I believe you will be golden.
Try and get your fan speed lower see if it helps or hurts.

njtommy

Do you have this info?
What size piping and what pump do you have going to the coil?

giantsean

I left the stat in there for a bit and it got up to 99, so that's pretty close. For laughs I set the fan back to its correct setting and it went down to 93, later up to 99. Note again these are not directly after the coil but downstream about 15 feet at the register opening. I did notice the return temp is lower at the "wrong" setting so maybe that's the way to go. What sucks is I lose out on stacking W1-W3 if I leave it there, but I guess at this point it's better than replacing the entire AH.

I did some testing with heat calls to both 1st floor zones and unsurprisingly there is a pretty good reduction in velocity with both of them open. Wondering if in retrospect it wouldn't have been better for me to just do one zone and eliminate all that extra plumbing. Still would be long runs to one end though, and at least the far end stays warmer (better insulated)

The circulators are Taco model 0015-MSF2-IFC. Piped with 3/4 copper from the loop to close to the AH and then switching to 3/4 PEX before switching back to 3/4 copper to enter the coil (which itself has 3/4" inlet/outlet). The circulators are both set to the middle speed so I could try to set it to max and see if it makes a difference. I am starting to think my CFM's are the limiting factor though.

Either way, it's going to be a FRIGID Sunday in CT. We shall see how we hold up.

giantsean

just tested at the registers again... only 85-87 now at full blast. Of course it's 10 degrees out tonight but that's kind of the point. Maybe this setup is simply underpowered or my duct design is total crap.

njtommy

They probably should of ran 1" copper. Due to needing a higher Gpm rate for the coil. Typically 3/4" copper is good for 4gpm and 1" would be 8gpm. Looking at the chart it looks like you need 9 gpm.
I would imagine your only out putting about 35,000 btus or so.

Is the boiler staying running with a consistent supply water temp?

giantsean

Yeah I figured that was coming too What I don't get though is that if the coil is only 3/4" wouldn't it already be it's own biggest restriction?

Would bumping up the circulator to highest speed help? I also think I mentioned that the supply is actually hooked to the coil outlet (plumbed backwards). From what I've learned this is a crossflow coil but I wondered how much difference it actually makes.

The boiler is holding much steadier now that the high return setting is enabled. It will dip from time to time but holds between 175 and 185 fairly well.

I also wonder if the basement environment is affecting things. It is unheated and pretty leaky. The ductwork is insulated w/ R6 or R8 (which I'm sure makes no huge difference). Still, I was getting 99 in one duct earlier when it was 10ish degrees out and now only getting 85 when it's close to zero out. The water is plenty hot, the wind is there (at least enough to feel it)... where is the heat???

njtommy

I would swap the supply and return lines. To see if that makes any difference. If you feel you can do the job you can pick up the tools to swap the pex lines at Home Depot. They are marked that way for a reason.

You maybe able to call Trane and ask them. About the coil piping.

I was always told don't go by tapping size go by pipe size and gpm you need. You can try to speed up the pump and see if it helps.

Is your floor insulated between the basement and the first floor?

Having duct work insulated helps.

kcopp

How leaky is your duct work? Are the seams taped and or painted w/ mastic? that could mean +30% loss of the air flow.... or do you have excessive runs of flex?

SWEI

Can you post photos? One of the air handler showing the piping connections and one or two angles on the boiler with surrounding piping and pump(s) would be helpful.

thanks!

giantsean

10:30 am update - left the downstairs set at 65 and walked into zone 1 reading 58 and zone 2 63. Clearly it was running all night continuously. To it's credit, the 2.5 ton TAM7 running the upstairs was able to maintain 70 (it is installed in the attic)

@njtommy - I can try to muck around with the piping but not sure I'll have time to do it before I see whether it makes a difference, as it's supposed to warm up soon. I also upped the circulator speed so we can see.

@kcopp - all the cardinal sins of bad install are present (except maybe not insulating at all). The metal runs are not wrapped/sealed and the longest run of flex is probably 20+ feet. I guess where I trip up though is on the volume vs temp. Wouldn't some hot air (not tepid air like I'm getting) be getting to the registers at the right temp?

All that being said, this is a masonry house which was never particularly well insulated (I would say the walls about R12-13 all around). The cellar is extremely leaky and it's cold down there. The ceiling joists have no insulation and there are areas where sills need air sealing. The house is still actively being renovated so is not airtight be any means, but if this happened before I put in new windows and doors and insulated masonry walls I could probably accept it more :P I grew up in this house and when we were kids it was always toasty w/o any insulation. Granted, this was when it had cast iron rads and an oil furnace (which I sorely miss right now!)

Thx again all!

njtommy

I'm not sure what they would install the 2.5 ton system up stairs that is less square feet. Was a heat loss done on the house? I'm assuming at this rate the install company has walked away from this?

giantsean

the "kinda" manual J that was done (not by them) called for 4.65 tons of cooling and I think 80K BTU's for heat. I think their reasoning was that it would get hotter upstairs in the summer hence the higher cooling capacity. It seems though the heat was kind of an afterthought for them, although I insisted (several times) that I wanted it WARM. They less walked away than I stopped paying them after several other issues (like running a piece of flex for like four feet with nothing but insulation (must have cut the liner short) and installing the condensers right in front of the electric meter, causing me to fail inspection.

Would replacing flex w/ metal help get hotter air to these registers? Or just more volume?

giantsean

Sorry here are some pics

John Mills_5

Drywall dust is so fine looking at a filter, it may not look bad but could be highly restrictive especially with a 3M. Change the filter OFTEN, even daily if there's a lot of construction going on.

njtommy

I run hydroair at my own house fed by a Navien combi. It keeps us very warm and toasty.

Round duct is always better then flex. It is less resistance then flex duct.

That's a pretty rough looking install install.

giantsean

Just out of curiousity how many sf is your house and how much heating output do you have?

I had a friend over yesterday who is HVAC certified but was mostly a tinknocker until he left the industry. He spotted several problems w/ the ductwork that would affect flow but his biggest question was how there could be so little actual heat produced from this coil at the registers. He also has hydro and told me just based on the size and output alone it should be warmer than it is. That there is no need to push such hot water through if it's working as designed. When it gets warmer later this week I plan to swap the supply from the coil outlet onto the inlet where it is supposed to be. I am really hoping it makes a difference because otherwise I am out of ideas.

I do plan on optimizing the flex runs and perhaps re-doing some of the ductwork. I am not even opposed to getting one more AH for the other side of the house if this one can't move air down the other side. But by the numbers it seems like overkill

njtommy

My house is a single story 1800sq ft. Heat loss of 45K( slant fin app).
Supply air temp is 100-105 depending on my reset swt max of 160. ( I really need to up size my coil to be able to run 140 max supply water and get lower return water temps.) I get run of 2 cycles per hour and 30-40min total time heat set at 68f.

Your house should be nice and toasty. I really hope swapping the supply and return makes a difference.

njtommy

@Hatterasguy

I did it based on 5 degrees design day. Summer time I use about 6 therms for DHW.

Last year I did a heat loss by usage as per @Robert O'Brien article and it came out to be 40k heat loss.

giantsean

So no big surprise that today was warmer and we were able to get up to 68 today with about 98 register temp. It appears that the system starts having trouble keeping up in the low 20's and below. Is this more a function of conditioned space heat loss / cold air infiltration or does the coil / output just get colder as the basement gets colder?

giantsean

Hey guys sorry I am still playing around w/ the idea of moving to 1" piping to the coil. Just had a couple more questions:

- The outlet from the loop to the circulator and from the return back to the loop are 3/4 copper... will these cause a huge restriction ie I need to re-do the loop?
- If not, should I see an improvement by just going to 1" PEX and trying to eliminate elbows where I can?

If I have to swap supply and return to the proper spot, I might as well do what I need to do when I have it all apart.

Thanks!

njtommy

Yes you would have to repipe the copper to 1" as well.
I hope you can get this solved.

giantsean

Thanks Tom I do too (at least without having to upgrade the entire unit lol). Re-piping the whole thing in copper may turn out to be a summer project though.. in worst case maybe I can try some 1" PEX and try to eliminate elbows where I can for now, just to get by.

Sincere thanks for your and everyone's valuable help!

njtommy

Yes try and do what you can.
I don't think you have to replace the unit. As long as you have enough air flow you could install a coil in the duct work. No point in replacing the $$$$ air handler.