zone not heating

Pension Lover · December 2003

I have a hot water baseboard heating system with a natural gas fired boiler, five zones, each controlled by a Honeywell zone valve, one B&G series 100 circulator. I am heating three floors with 32 vertical feet from the boiler to the baseboard in the uppermost zone. The circulator is on the supply side and there is a B&G air separator between it and the boiler. The tank is piped into the air separator. The air separator is new. The circulator is a year old. The steel tank facilitating the balance of pressure (maintained at 20lbs) is two years old.

There are two zones on the first floor. One of these zones has been slow to heat. This morning, the coldest of the season so far at 17 degrees F, saw the room temp of the slow-heating zone at 59F and the thermostat was calling for 67F. The call for 67F would have initiated one hour earlier. The disparity between the thermostat's request for 67F and the room temp of 59F was the most I've seen this season. (As of this moment, nine hours later, the room temp in this zone is 63F. The thermostat has been calling for 67F for the entire nine hours. When the outside temp is in the 40's and lower, this four degree difference is as good as it gets.)

This morning, when I went down to the boiler room, the valve to this zone was open. I tested the end switch to see the lever on the back move from open to closed and back to open, and the circulator behaved as it should by starting up when the valve was open and shutting down when the valve was closed.

Three of the other zones were calling for heat at that same time. The fifth, and uppermost zone was not calling for heat because the room temp matched the thermostat's setting.

What am I missing?

Jim Glose

Paul_11 · December 2003

questions and suggestions

Hi,
If all the zones heat fine but one you would think that your near boiler piping is OK but still I wonder about that steel tank you mention. Is it one with a rubber bladder inside or is it only a steel tank?

Can I assume you have bled the zone and you have no air in it?

Have you tried to isolate the poorly heating zone by closing the control valves for all of the other zones that do heat up to see if that increases how fast this troublesome zone gets hot? That may tell us something.

Paul

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Einsiedler · December 2003

balanced?

Does the problem zone heat when its the only one calling? or never warms up??.

if only a problem zone while others are calling. the system may be in need of balancing. If there are any balancing valves (or even globe or ball valves) on the return of each of the zones, you could try slightly closing the valves on the zones that are heating ok. This increase in pressure drop (on the good zones) will create more flow in the problem zone.

another thing to check is the delta-T across each zone (what is the difference in temps from supply to return for each zone). if all are reasonable and the proble zone has a really high diff. It is starving for flow.

hope this helps.

EIN

Earthfire · December 2003

air?

have you checked that problem zone for air ? try bleeding or purging it

Radiant Wizard · December 2003

Delta-T

Start with the obvious. What is your Delta-T? That is the difference between your supply water leaving the zone and your return water coming back.

JohnNY · December 2003

It sounds to me like the problem zone is underradiated or isn't getting proper heat transfer from the existing radiation. I doubt this is going to be an air problem by that description. To me, the problem being accentuated by a drop in outdoor temperature sounds a bell.

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Pension Lover · December 2003

Hi Paul,

The tank does not have a bladder. It's just a big steel tank hanging from the ceiling.

I haven't had time to take the actions as suggested by you and the others who have been kind enough to respond, but I will report back with my findings.

Jim

Pension Lover · December 2003

EIN:

I'll look for balancing valves.

What tools or process do you use to take the temperature of water residing in a sealed pipe?

Jim

Larry (from OSHA) · December 2003

is this situation new

or has this been going on in years past? is the baseboard getting as hot as the other ones. has anything changed or work on the system. i appologize for asking the obvious, but sometimes.........

Larry

Pension Lover · December 2003

John,

Improper heat transfer?

You mean if the baseboard is covered by 3,000 stuffed animals? Or, perhaps clothing, be it clean, dirty, or decaying? My teenagers cleaned their rooms on Saturday, and the problem still exists. . . are there other things that contribute to improper heat transfer?

Jim

Pension Lover · December 2003

Larry,

The problem began at the tail end of the last heating season.

Jim

JohnNY · December 2003

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JohnNY · December 2003

Lets just....

...wait until Noel (the slant/fin guy) gets here.

But yes, that's the kind of thing I mean. Air has to flow freely around the enclosure. Lot's of homes I'm in are just in need of a decent vacuuming of the elements.

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[Deleted User] · December 2003

Have you

tried manually opening the zone valve?

Paul_11 · December 2003

temperature guages

It is a good practice to install temperature guages on the supply and return lines of all zones. That is what I do on all the work I design. It is also one of the first things I would suggest when I am trouble shooting a problem like this. With them it becomes easier to monitor the different temperaturs of the different zones and monitor any changes.
I like the ones that have wells with removable guages so it is easy to replace them when they break.
Paul

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Pension Lover · December 2003

Ron,

I did this, but was hit by another brain storm (that I thought would surely be the solution) and impatiently moved on.

As is often the case, whatever the brain storm was, it didn't work.

It's funny that I never get a brain storm that says "be patient". The two must be mutually exclusive.

I'll try again. Thanks.

Jim

Unknown · December 2003

Hi

The temperature difference is the key thing, here.

How many feet of actual finned tube is on a single loop to and from the boiler?

If you have 34', you should see about ten degrees drop from beginning to end of the loop.

If you have 67', you should see a twenty degree drop in water temp.

If the water temp isn't dropping the right amount, it points to low air flow, if not enough drop; and to low water flow rate if the drop is too big for the length of finned tube.

It could be carpet covering the inlet opening, or something on top of the fins covering the outlet opening.

It could be not enough baseboard.

It could be the water temperature is too low.

The water temperature difference is the key to it.

Noel

Radiant Wizard · December 2003

I asked

that question above. I guess he didn't want to reply.

Pension Lover · December 2003

Radiantwizard,

Please accept my apologies. I had more of a response than I expected, and thought that I had replied to each one. It is my mistake entirely for not acknowledging your gesture of help.

Yes, I did see your message regarding Delta-T and intend on taking those readings. I will let you know the results. Thanks for taking an interest in my situation.

Jim

Rob T · December 2003

Noel,

thanks for that info as it helps answer a question I had about the low Delta-Ts I am getting. (Approximately 5-7º on one of my zones that has about 40' of fin.)

Sorry about hijacking this thread.....

R

Unknown · December 2003

What water temp? That's pretty close.

With lower temps, the board puts out less heat, so you can run more length and be within the 20° F Delta T.

The limit for 3/4" pipe is about 40,000 BTUH, if you are looking for a 20° F Delta T.

Noel

Pension Lover · December 2003

Earthfire,

My wife and I are going out to dinner on Saturday night, and to a nice restaurant none-the-less! It'll be the headline in the Sunday morning paper: "HUSBAND FINALLY TAKES WIFE TO DINNER, LONG SUFFERING SPOUSE ON CLOUD NINE". That will help to balance the scale as I spend time in the boiler room this weekend . . . I'll put "purge air from zone" on the list of things to consider.

Thanks,

Jim

zone not heating

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