Viessman 100-W B1HE-199. New install, Help!

Steltz

Hi all,
Would appreciate some help here, as my plumbers response to this issue was "this is normal." The system that primarily heats my house is two hydro-air units (70k btu coils in each). Up until recently I had a large high mass oil boiler. He just installed the above about 5 days ago. The issue is the vents are blowing cold for longer than I would expect (10, maybe more minutes, though haven't tracked that closely). I understand why it's happening, but still seems rather silly. The DHW options on the boiler is looped to my indirect tank, which is heating house water to 140, and then put a mixing valve on top to provide at 120 so no one scolds, and we have endless hot water.

What are my options on the cold air handler blowing until there is enough hot water pumping through coils?
1. Does anyone put an aquastat on this type of boiler so it maintains enough temperature? or that will just cause overcyling?
2. How can this be wired so when the thermostat calls and the boiler clicks on, the air handler will only cycle on when a certain temperature is reached? We installed with the Viessman low-loss header and there is a port in there. I was thinking could an aquastat be wired and set into there and zoning relay (Taco 6 zone switching relay, SR506-4). We set the supply at 180, I was thinking at 150 in the header the air handlers could come on.

Please forgive if any of the above is total nonsense....I am a total noob.

Thank you!
David

GGross

You should be able to wire an aquastat as a low limit to interrupt the call for heat to the air handler, which should stop the fan from coming on when below a certain temperature. It sounds like the boiler is functioning correctly, you just don't want the air handler fan running when it is full of cold water.

EBEBRATT-Ed

Use a strap on aquastat on the air handler's outlet pipe (return pipe)

The aquastat make on a temperature rise. Set the make temp at 120 or so and the differential or off temperature at around 90. You can adjust it. When the pipe is hot the fan runs for heat. You can do the whole thing at the air handler. Wire it to break the heating wire at the air handler. Your plumber should know this

Honeywell L6006C1018 @ supply house .com

Ironman

Taco also has an AHU control that can accomplish this.

The ODR curve on the boiler may need to be adjusted for the higher SWT that a fan coil requires.

Steltz

I have one issue running it at the air handler. One AH is in the basement 10 feet from the boiler (first floor zone - easy). The other air handler is in the attic that feeds two zones (attic and second floor), which is not so easy to run an aquastat to my switching relay board (I assume that's where it would connect....).

Ironman

No, it just needs to go to the AHU to hold the fan off until the coil gets hot. A relay may also be needed.

hot_rod

The temperature control could be on the return line from the AH, it doesn't need to be right at the AH. It could be in the mechanical room if the piping comes from the AH directly to the AH.

Or some fan coils, like kickspace heaters have snap on the pipe or coil itself in the unit. The fan wires thru it, power is off until it reaches temperature.

Here is an adjustable style, they make a U clip to hold them on a round tube also.

mattmia2

Maybe see if the air handlers have multi speed motors or change to one so you can run high/low based on water temp and get some of the benefits of the mod con without feeling cold and drafty.

The cheapest up front solution is to raise the swt from the boiler, the more efficient and probably ultimately more comfortable as far as longer cycles and more even heat is to slow the blower down most of the time. Maybe can even reduce the high blower speed some.

Steltz

In the height of the winter months, does it make any sense to have an aquastat on the boiler to maintain a minimum temp? It isn't too many feet of pipe (supply and return manifold and primary loops maybe 16 feet of 5/4 copper pipe). Or would I destroy efficiency? My house, at the moment, is not very well insulated.

GGross

Steltz said:

In the height of the winter months, does it make any sense to have an aquastat on the boiler to maintain a minimum temp? It isn't too many feet of pipe (supply and return manifold and primary loops maybe 16 feet of 5/4 copper pipe). Or would I destroy efficiency? My house, at the moment, is not very well insulated.

The "next level" of Viessmann equipment likes to operate using a constant circulation, while maintaining a supply temp based on ODR, the zones operate independently from the boiler, contractors hated it in my area. The well on the low loss header is used for the supply temperature sensor. This is part of the difference in operation between the vitodens 100 and vitodens 200. You could run an aquastat to maintain that temperature sure, it won't quite function the same way the vito 200 does, in that the control knows the temperature in the low loss header, knows the temp outside, and what temp is needed to heat the space, and can fire accordingly.

EBEBRATT-Ed

@Steltz

Read the above comments. You can put the aquastat at the air handler and any wiring needed can be done right there.

The aquastat controls the fan. Leave the boiler and it's controls as is. The aquastat starts and stops the fan as the pipe heats and cools....simple

No need to complicate things

Steltz

@EBEBRATT-Ed Thank you. So I'll need two aqustats installed on the PEX lines and wired to the fan of my AH? Or can it be wired to the zone relay?

Separately, I want to confirm this won't mess with the fan when it's AC time.

Thank you!

Ironman

Steltz said:

@EBEBRATT-Ed Thank you. So I'll need two aqustats installed on the PEX lines and wired to the fan of my AH? Or can it be wired to the zone relay? Separately, I want to confirm this won't mess with the fan when it's AC time. Thank you!

Please read mine and others comments: the aquastat controls the fan at the AHU, not the zone control. It holds the fan off until there’s hot water in it.

And yes, it needs a relay to allow the fan to function when it’s not using the hydronic heat.

Your contractor should know how to do this.