Vitodens 100 W-30 Boiler Temperature Setting Help Needed

Jake48

I have the boiler set at the normal which is the Max setting of 176 degrees.  This works great in winter for my house as it meets our heating and hot water needs great except the 3-5 very worst days of winter where it struggles to keep up, but no big deal.

However, during the 7 warmest months of the year (April 1 - Nov 1), we basically don't use heat at all as we like to be cool with thermostat set at 60 degrees.  Also we all workout constantly and prefer cold showers after working out so we use minimal hot water.

My question is, should I be turning down the boiler temperature setting from 176 down to 140 or lower to save gas during the 7 warm months that we are not heating and using minimal hot water?  If we don't turn it down, the unit is staying from about 150 to 188 (it overshoots the 176) for 7 months and we barely need it so seems like a lot of wasted gas/money.

Also, are there any negative consequences to operating the unit at the lower temperature such as lower efficiency so not saving anything, or corrosion problems or other problems related to operating the unit below its normal design temperature that I am not thinking of?

icesailor

Vitodens 100:

It must be wired wrond or set up wrong. It should only come on in the warm months when the indirect calls. You do have an indirect don't you?

Did you set it up yourself or someone that installed it and didn't read the manual. I've not heard of that complaint. More here will reply.

CMadatMe

Old Version

This version has no outdoor reset so the boiler just runs the curve. I'd put the Como Ot on the boiler to get indoor and outdoor reset as well as the ability to run heating schedules. You can also add the domestic power pump module to gain control over the domestic hot water.



Is this boiler piped primary secondary or did the installer use a low loss header? Boiler will only make 6.2 gpm and you need one or the other to pull out all the boilers capable and listed btu output. That may be your problem for those cold days. A picture tells a thousand words.

Jake48

Vitodens 100 W-30 Boiler Temperature Setting Help Needed

I have an indirect hot water tank (Superstore 40 gallon).  The whole system was installed by a contractor that was trained by Viessmann.  When hot water is demanded the pump comes on and circulates the 176 degree water from the boiler to heat the water in the tank.  When heat is called upon, those pump(s) come on to circulate the 176 degree water.  My understanding is the boiler is supposed to be maintained at high temperature at all times.  You are saying the boiler water is at room temperature and shouldn't be heated up until the hot water tank or heat is called for?!!   Are you sure?  I would be interested in other opinions.

Jake48

Vitodens 100 W-30 Boiler Temperature Setting Help Needed

It uses a low loss header.  Do you have an answer to my original question?  During late spring/summer/early fall can I and should I lower the boiler temperature to 140 or lower?

CMadatMe

It's a

Condensing boiler. It can handle water temps much much lower.

CMadatMe

I Did

Answer the question. Como-OT to gain control of water temps and dhw pump module to gain control of domestic. It's a condensing boiler it wants and needs water temps far below 176 to ado what it is suppose to do. Condense.

Jake48

Vitodens 100 W-30 Boiler Temperature Setting Help Needed

Why doesn't the Viessmann manual mention installing either of those?  Why can't I just manually lower the boiler temperate in April and in late October raise the temperature.  Isn't that simpler, cheaper and easier than installing new parts that are not referenced in the installation manual and that are something else that could break?

CMadatMe

Sure it Does

They are accessories. How would you control the boilers logic? You have no influence on domestic hot water. The curve only has influence over heating. The boilers logic is to fire into high fire on a domestic call.

Jake48

Vitodens 100 W-30 Boiler Temperature Setting Help Needed

Any other opinions out there on turning down the boiler temperature during the warmer months?

Jean-David Beyer

turning down the boiler temperature during the warmer months?

With my boiler that has an indirect for my domestic hot water, I do not turn down the boiler at all.



The controls of the boiler do not fire the boiler at all unless there is a call for heat from one of (up to) three thermostats. The first (highest priority) controls the indirect. The other two control the two heating zones. When the indirect wants heat, the boiler fires until the indirect is satisfied, and then it stops. That is the drill during the summer.I estimate the boiler may fire about 20 minutes a day, though it may fire once at night. It takes less than 10 minutes to satisfy the indirect.



In other words, the controls do not keep the boiler hot at all times. It does have a freeze protection program in it so if the heat exchanger gets below 40F it fires the boiler and runs the circulators selected. The boiler circulator and the radiant slab are selected. It shuts off again when the heat exchanger gets to 45F. I imagine my indoor thermostats would call for heat before that happens, but you never know.



This month I burned 4.18 therms for hot water. Last month I used 4.17 therms. If I were to lower the temperature of the water to heat the indirect, it would have to run longer, so I am not sure lowering the temperature would save much. That cost me $3.11 for the gas, $2.20 for the delivery, and $8.25 for the Residential Customer Charge (that is the same whether I use any gas or not; consider it the cost of renting the meter).

Jake48

boiler temp

You said:

"In other words, the controls do not keep the boiler hot at all times."

My boiler is staying hot all the time at around 176 degrees even though the indirect hot water tank is calling for heat only twice a day for about 5 minutes.

Why the difference?

Also I used 20 therms in august which includes the gas drier for an active family of 4 and gas stove which is used about 12 hours a week so we can't directly compare gas usage.

Jake48

boiler temp

PS JBD, is your boilier a condensing boiler or regular one?  If yours is a regular one, that may explain why yours is off when not in use and mine stay at temperature at all times.

CMadatMe

Boiler Does Not

Just sit and maintain a temp all day. Because the old WB1A does not utilize outdoor reset it rides the curve that was set unless there is a domestic call. On a domestic call the boiler goes right into high fire to satisfy the domestic need.



I will say it again, you can play with the curve from three ways until Sunday and it has no influence on the making of domestic hot water. You want control of the boiler then you must get a 7249 069 0-10v module, the Como Ot, outdoor sensor and the dhw pump module.

Jean-David Beyer

PS JBD, is your boilier a condensing boiler or regular one?

Mine is condensing. I think what really matters in this case is not the modulating or condensing, but that it is cold-start. Unless your boiler is not cold-start, I would infer somethng is wrong with it; e.g., defective control or incorrect wiring perhaps.