mod/con retrofit w/fintube: water temp now too low?

JohnnyCB

Hi all,



In case you read my other thread I'm the guy that had an old oil-fired boiler replaced with a Vitodens 100 natural gas boiler and asked about the ball valve in the primary loop...



Everything works, except that zone two (the main floor of the house) takes quite a while to come up to temp on most days.  For instance, the thermostat cuts back to 60 degrees at night ( no bedrooms on that floor) but sets to 68 for the day.  In can take anywhere from 3 to 5 hours to reach the goal room temp.  It stays there all day once it gets there without much trouble.



What I've noticed is that the baseboard rads (3/4" fin tube) do not get as hot as they used to with the old boiler.  I'm *guessing* the old one put out 190 degree water or so, but running the Vitodens with the temp control on "reset" only gets the temp up to the low 170s.  This might not be affecting the upstairs zone simply because it's small, and since the downstairs heat rises it takes less effort to heat.



Does this seem like a reasonable assumption?  If it does, what are my options for adding in baseboard or small/thin rads that will work efficiently at this temperature?



Thanks in advance!



-JohnnyCB

icesailor

Room Temps:

That's a reasonable assumption.

I suggest that you close all the doors to the upstairs rooms. It will stop the heat from downstairs from going into the upstairs rooms. It will then gather in the upstairs hallway. If you find that the heat downstairs works better, you will then have your answer.

Remember, if you leave the upstairs doors open, the cold air from those rooms will fall down the stairs to be heated by the downstairs heat emitters. That makes them theoretically smaller, while making the upstairs ones bigger. When you make areas as zones, and you do not separate them physically when the connection is vertical, the whole system becomes unbalanced.

You can't fool Mother Nature or re-write the laws of physics. 

Robert O'Brien

Don't setback

the room temp so much,let the reset control do it's job!

CMadatMe

I'm with Rob

Let the boiler do its thing. If you really want to add to savings down the road. save your pennies and add the Como-OT to the boiler in replace of your main zone thermostat. Will provide indoor feedback to the boiler allowing you to fine tune it in to the zone.



The problem with setback is that we are accustomed to shoving 180 degree water through fin-tube that is generally overrated for the room and is not needed on any day except for the coldest day of the year and the great Americans we are we want instant satisfaction. Let the boiler do it's thing...

Steve Whitbeck

Temps

I don't believe the older Vitodens will go hotter than 170*.

One of the reasons I didn't sell them.

JohnnyCB

This is a new Vitodens...

It does go above 170 - just not above 180.



Maybe water temp isn't the issue.  Maybe it is.  (shrugging)



For now I'll try setting the setback to only 5 degrees down instead of 8 and see if it helps at all.



I was also curious (since I plan to add radiant or more efficient baseboard or rads to a kitchen remodel and possibly other rooms) as to which products out there have good efficiency at ~170 water temps or less?



-JohnnyCB

Mark Eatherton

The main problem is...

Your thermosta thinks that every time it calls for heat, that the heat source will projectile VOMIT heat into the space, like your old one did...



The new boiler dribbles heat in only enough to satisfy the call for heat, nothing more, nothing less. When you do a deep set back, the boiler struggles trying to get the house caught up, andit really has no idea how bad the deal is either. The boiler and the thermostat understand one language. ON versus OFF. Your home either needs heat, or it doesn't.



Now that you have this very intelligent boiler, I would recommend that you tighten the place up with caulking, insulation etc, get rid of any deep set back programs, and let the boiler do its thing.



ME

CMadatMe

You Picked

The wrong boiler.



I hate to say but if you planned on radiant the Vitodens 200 was the boiler to pick. Can run multiple heating circuits. If you do run radiant I would suggest you look into the Como-OT for that zone..



I also just picked up on your original post concerning the ball valve and went and looked at the previous post. If there is no low loss header on this boiler then that solves your problem in a nutshell for me.

icesailor

The main problem is/That doesn't wash:

Mark, I still don't buy yours and others arguments.

If the temperature drops 15 degrees outside in an hour, what does the boiler do? Is it capable of keeping the zone temperature up at the setting when the temperature outside drops? If it doesn't, there's a lot of PO'ed customers. Of course it does.

There's no difference between the outside temperature dropping 10 degrees or the room drops 10 degrees.  Or the opposite.

If I keep my house at 70 degrees for 24 hours a day, I will use a certain amount of fuel. If I drop my house indoor temperature to 60 degrees, I will save money on fuel. That's a given. If I set my thermostats at 65 degrees, I will save 1/2 as much as I would as I would at 60. If I set my setback thermostat at 70 degrees for 12 hours and 60 degrees for 12 hours, my heating system is seeing an average indoor temperature of 65 degrees. The boiler and controls should be able to figure this out, If they can't, someone needs to resolve it or the systems are just junk.

If automobiles can do it with computers, changing A/F ratios, ignition timing and combustion controls, it isn't a far step to doing it on a heat system.

icesailor

The main problem is/That doesn't wash:

Mark, I still don't buy yours and others arguments.

If the temperature drops 15 degrees outside in an hour, what does the boiler do? Is it capable of keeping the zone temperature up at the setting when the temperature outside drops? If it doesn't, there's a lot of PO'ed customers. Of course it does.

There's no difference between the outside temperature dropping 10 degrees or the room drops 10 degrees.  Or the opposite.

If I keep my house at 70 degrees for 24 hours a day, I will use a certain amount of fuel. If I drop my house indoor temperature to 60 degrees, I will save money on fuel. That's a given. If I set my thermostats at 65 degrees, I will save 1/2 as much as I would as I would at 60. If I set my setback thermostat at 70 degrees for 12 hours and 60 degrees for 12 hours, my heating system is seeing an average indoor temperature of 65 degrees. The boiler and controls should be able to figure this out, If they can't, someone needs to resolve it or the systems are just junk.

If automobiles can do it with computers, changing A/F ratios, ignition timing and combustion controls, it isn't a far step to doing it on a heat system.