Uneven hot water heating

[aloren]

I have a NTI-Trinity condensing hot water boiler heating three zone on three levels (basement radiant heat; first and second floor cast iron radiators and a couple of fin radiators). Its a completely new system with new piping to all radiators (radiators are original).

The problem is this. When the temperature drops below about 30 and all zones are calling for heat, the hot water flows only to the first and second floor bypassing the basement entirely. Naturally, the basement zone temp drops (to below 50 or less). When zones 1 and 2 no longer call for heat, the basement starts to get hot again. But, being that its cold outside the first and second floor call for heat again before the basement reaches 60 (by the way the basement is radiant heat in a new slab with insulation underneath). This is not an issue when the temperature outside is in the upper 30s.

The system has three pumps: an Taco pump, and a zone pump for each of the three zones. The pumps seem to be the proper size and seem to be working fine.

I've been told I can solve the problem in one of two ways.

First, by creating more head by restricting the amount of hot water flowing to zones 1 and 2. I've tried this route first. I've retricted the water going to the other zones by almost 80%, and its helped. The basement now will heat to 66-68 range. Still on exceptionally cold days with temps in the mid twenties, the problem resurfaces and the basement drops to about 60 degrees.

The second option suggested was to have a fourth pump installed.

What is going on here?

Do I need a fourth pump to force the water into the basement loop?

Shouldn't adding heat to the system by shuting down flow to zones 1 and 2 have solved this?

Do I need self-regulating valves to stop and start flow to the other zones?

Any suggestion would be much appreciated.

[simpleman]

First we would need to know the heatloss of your home.
What was the indoor and outdoor design temps?
Second we would need to know the total of btu of your emitters.Infloor and rads.

Also need to ask does this boiler modulate its btus,and when all zones are calling is the boiler running wide open.

Is there a boiler reset that adjust the temp depending on outdoor temps?

[beenthere]

Telling us you have 3 circs, doesn't tell us how they are piped, or how they are controlled.
Need alot more info.

[Dof3]

Possibly to small a boiler. Need to know your heat losss and what size piping to each zone?! Is it P/S piping setup? Are there mixing valves on the infloor zone?

[sweet]

Is this system piped with primary /secondary? Meaning,is there a seperate circulator controlling the boiler loop, seperate from the system pumps?

[jdenyer]

Also is the radiation in the basement adequate? Was a load calc done when this was all put in? Oops I see Simpleman already asked that

[aloren]

Thanks to all who replied. Much appreciated.

I'll try to answer your follow-up questions as best I can since i may not have all the information at my finger-tips.

Boiler modulates its btus, and runs wide open when all zones call for heat.

Boiler input is 50-145,000
Boiler output is 48-138,000 (roughly equivalent to but slightly under boiler I replaced)
Max water temp 200 F


There is a thermister (resister sensitive to outdoor temperature) and a control with the unit. Outdoor sensor tells control the outdoor temp and control adjusts per pre-programmed settings.

There are mixing values for the in-floor zone. and valves for each radiator by the way.

System has primary and secondary piping with separate circulator for boiler loop which is separate from each system pump.

Heat loss calculation and total btus of emitters was done but I don't have them here. I'm assuming this was done properly and that boiler is properly sized.

House including basment is @ 3200 sqft; its old but well insulated with new windows, and basement subfloor is insulated.

Pipes to rads are probably not properly sized - 3/4 and not 1 inch. -- this was done by another contractor.

Re your heat loss question -- I have a followup question. I installed the boiler two years ago. It replaced an old boiler and gravity fed system and all the old blackpipe was replaced with new copper. This prior system worked poorly all the time -- heat wasn't getting to all the radiators (even after bleeding and taking other measures). All the piping in the boiler room was replaced again after determining that we needed a primary and secondary loop and a pump separate from the zone pumps, and we added can vents (there were none before but the system was bleed to get all the air out).

Even though, before all this work was done, not all the rads got hot, each zone was adequately warmed in some cases too hot (some of the rooms with rads that got only luke warm didn't heat up all that well).

In otherwords, I didn't have this issue with one zone not receiving any hot water when the other zones called for it. Now, I do.

What I don't get is why heat loss would be a factor if, prior to redoing all the piping the second time, each level got heat even if not every radiator did.

Again thanks for sharing your knowledge and advise.

[beenthere]

How long are the in floor loops, what size, 3/8", 1/2", 5/8", and what size circ are you using for the in floor.

Do you have thermometers on the radiant, is so what temp water are you trying to use.

What make mixing valve.

[hot wired]

do u have balance vavles on does unit have a bypass on it

[Edited by hot wired on 03-10-2005 at 05:42 PM]