New Viessman 100 not satisfying thermostat

Jim Franklin

I have a new unit with outdoor reset, 2 FHW zones in a 60s 1500sf raised ranch in Massachusetts. No heat loss calc was done. The unit was doing fine when I had the house at 45 while it was open for renovation, but now I'm moved in and want it a touch warmer. Tstat is set for 65 but I can't get the 2nd floor beyond 57. The display indicates a water temp of 137 and I can hold my hand on the supply pipe for 2 secs and return pipe for about 6 seconds. I bumped up the unit's temperature from the factory 68 to 74 with no change. Tankless DHW is fine, showers are great.

There is a variable speed Grundfoss circulator on the primary loop and it's in Auto mode, displaying 9w, 1 gpm.

The house has marginal insulation, r-8 in about 75% of the walls (the other 25% are empty awaiting blown in cellulose) and the attic insulation is missing in a few places and very compressed in others. Windows are new and most drafts are sealed but not all. In my opinion it has too much baseboard, they just ran it along all the long walls. Yet it seems like not enough, or it's not radiating, given how hot the return pipe is at the boiler. The pipes leading to the baseboard are hot but the fins don't feel hot at all. I vacuumed them and they're free of debris.

I'll call the installers in the morning but hopefully someone has some insight so I don't freeze my as soff again tonight, or even discussion for me to read while I can't sleep.

thanks,
jim

newagedawn

why wasnt a heat load done, never put a boiler in when you dont know the heat load, thats an expensive guess, it sounds undersized to me, also could be a reset issue, not allowing the water temp to get higher in colder weather,hope you found competent installers to troubleshoot it

SeymourCates

@Jim Franklin

The problem has nothing to do with heatloss and the boiler is not undersized. One only needs to see the SWT at 137F to realize this. Have the installer adjust the heating curve so a bit hotter water is provided across the temperature range. This is an iterative process and you should observe the procedure to accomplish it yourself in the future. The technician cannot get it right on the first attempt unless he goes overboard and kills the efficiency of the unit.

Jim Franklin

I did this myself, going from 68 to 74 last night (on the unit, not the room tstat). Is that too small a change?

Jamie Hall

It's the outdoor reset curve which needs to be tweaked, not the thermostat or call temperature. If you can find the manual, that may show you how to go after that curve. It's kind of buried away in the controls.

Jim Franklin

That's what I've been saying. I tweaked the temp on the unit, which the manual says adjusts the heating curve. Although the factory setting of 68 is very near the max of all the curves (176), so I don't think I gained much by bumping it up to 74. Boiler water at 132 or 147 should still bring the house up to the tstat setting of 65.

Simply Rad

I think one large detail is being over looked with the structure not the boiler and distribution system....the homes insulation. Jim said 25% of the walls are still waiting for insulation? Also, address the attic insulation. Finish the insulation and the system will work better and save you fuel cost! Also, try setting the Grundfos pump to a different setting and see what happens. Set it on the high constant pressure mode and see what happens

Brewbeer

Photos, please ! Let's see the boiler and near boiler piping, and let's see your radiators.

SeymourCates

@ Jim Franklin

Return what you believe is the setpoint to 68 (factory setting).

Go into the program and change the slope of the heating curve from the factory setting of 1.4 to 1.8.

page 12 in the manual:

https://www.viessmann-us.com/content/dam/vi-brands/CA/pdfs/doc/b1ha/vitodens_100-b1ha_oi.pdf/_jcr_content/renditions/original.media_file.inline.file/vitodens_100-b1ha_oi.pdf

Observe the system for a couple of days before making any further changes.

Photos are not required.

Jim Franklin

Seymour that version of the manual is apparently not given to homeowners :-) Mine just had the simplified version where you can change which curve is used (via the arrows on the display, no menu diving required) but not alter it's slope. Thanks for the link.

I believe that's what they did today and the house warmed up in a hurry. Once the insulation is installed in a few weeks I'll revisit this in case it needs slacking off.

Thanks all!

jim

ced48

Why are you not getting the guy who did the installation back? Isn't it his job to give you a heating system that works?

Henry

Never, ever show a home owner, apartment block owner or janitor how to program a boiler. It is the perfect way to get callbacks. I had one son of a large apartment block owner that took a heating course. He found out the code to enter into the programming mode. He knew better than our people. I had reduced the boiler size and provided a condensing boiler. The first two months, we go several calls to reprogram. Also gas consumption went up. My tech takes notes of the settings. They have been changed. Call the owner and explained that he was going to get billed for the calls as his on is playing with our boiler. And if he touches it again, there is no warranty. Problem solved.

ratio

Henry said:

...if he touches it again, there is no warranty.

I love that sound!

Rich_49

Henry said:

Never, ever show a home owner, apartment block owner or janitor how to program a boiler. It is the perfect way to get callbacks. I had one son of a large apartment block owner that took a heating course. He found out the code to enter into the programming mode. He knew better than our people. I had reduced the boiler size and provided a condensing boiler. The first two months, we go several calls to reprogram. Also gas consumption went up. My tech takes notes of the settings. They have been changed. Call the owner and explained that he was going to get billed for the calls as his on is playing with our boiler. And if he touches it again, there is no warranty. Problem solved.

Nonsense . This gentleman probably hired one of the 975 out of 1000 EXPERTS . I have consulted and designed many systems for DIYers with a mechanical aptitude and those jobs look better than 95% of what I see on a daily basis . Your guys probably know what they are doing . We teach people here who are frustrated on a regular basis how to address their issues . Why would we not help this man get out from under the thumb of mediocrity ?

Meanwhile Seymour's find in the manual worked . Good job Seymour . You found the needed information and kept the thread to a decent length . Kudos .

Gordy

I think teaching the homeowner how to adjust the reset curve on “their boiler”is prudent @Henry. Sounds like the installer got a call back anyway. Maybe that could have been avoided with a little direction on how to use the ODR, and the full manual........

ratio

As another data point (and not to be contrary in the least! ) I have told customers about reset, explained how and why it works—in depth—and drawn pictures illustrating what is going on and still come back to find find the setpoints all screwed up.

Gordy

At least you tried @ratio that’s the important thing. If they screw it up you still get to come back, and explained why, and how it was their fault. To me that’s like keeping how to use the cruise control on a vehicle top secret.

Paul48

Does anyone see a problem with his selection for a primary circ?

bulldoglax

If you have outdoor temp sensor hooked up changing the set point on boiler screen will adjust the curve on the new 100 series. Riase it up a little and work down for comfort levels if no heatloss was done. Also agree with paul change the the heating loop circs from auto adapt. I don't know grundphos well but think you can set a either a pressure or constant speed.

ced48

Paul48 said:

Does anyone see a problem with his selection for a primary circ?

You can't use a variable speed pump with a modulating boiler

psb75

"You can't use a variable speed pump with a modulating boiler"

ced48, Are you really saying this? I use them ALL the time.

bulldoglax

I have a feeling he means delta t circs, which would probably be a bad idea, but yeah all we see are variable speed pumps on secondary zones. I would probably even prefer zone valves with delta p pumps for most residential applications.

Gordy

psb75 said:

"You can't use a variable speed pump with a modulating boiler"

ced48, Are you really saying this? I use them ALL the time.

On the secondary side yes. On the primary boiler loop no. Not with out proper logic between the modulating boiler, and variable speed circ.

Paul48

Right..........He said he was using an Alpha on auto adapt on the primary. He said it was running at 1 gpm, and with no changes in Delta P, it will run at that, all the time. N.G.

bulldoglax

If this is in fact a new vitodens 100The primary circulator is built in , three speed adjustable. Maybe he has pumps confused prim/secondary

ced48

I assumed we were talking about his setup-Of course you can use a 0-10V controlled by the boiler, but anything else will just confuse the boiler-

GW

Humm still unsure what the Alpha pump’s role is here. I guess we DO need a pic

Gordy

It’s fixed the obvious issue was the slope of the reset curve. 137 degree swt was big clue here.

GW

Yes the pump was just a side conversation