Little heat in one zone

Old 01-22-00, 11:52 AM
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We have a 5-zone boiler located in our garage with the first zone heating the water, and the other 4 directed to various rooms as follows: zone 2 is for upstairs living room, 3 is upstairs master bedroom, 4 is downstairs den (same level as boiler in garage), and 5 is for 3 bedrooms upstairs. We installed this boiler a few years ago and it has been working fine up until a few weeks ago. Zones 2-4 are working ok except for a slight degredation in performance that we can accredit to the colder weather. However, in zone 5, the 3 bedrooms, the temperature never reaches more than 62.5 degrees. the t-stat is set to 70 and even 90 with no change. these 3 bedrooms are located at the far end of the house (furthest from the boiler). we looked at the boiler and assured the pipes are hot for all zones, which they are. to test the valve for zone 5 we swapped zone 2 with zone 5 (t-stat, and electronic valve control) and no change. zone 2 was heated properly, but 5 was not. We set the boiler t-stat up to 207 degrees, the highest it goes to and still no change in that zone. what i noticed though is that when watching the boiler, zone 5 will turn on for 5 minutes, and then shut off again for another 5. i'm thinking that there may be something with the computer controller that controls the timing of the valves, but that would suggest that when i swapped the zones, the problem would manifest in the other zone, which it didn't. someone also mentioned that perhaps the boiler is automatically shutting itself down after 5 minutes because it is getting too hot. this sounds like a good possibility since there is more demand for heat during this time (especially now in new york), and plus the fact that we raised the core t-stat to 207 degrees. if this is true, will *lowering* the core t-stat to say 160 (where it was before) help anything. what else can i try to test to see where the problem lies? Any help is greatly appreciated. Thank you.

Alan Snyder

[This message has been edited by Alan Snyder (edited January 22, 2000).]
Old 01-22-00, 09:49 PM
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Hello: Alan Snyder

You have discribed your boilers symptoms completely and perfectly. I commend you.

My suggestions are:

Remove the T-Stat completely in the effected rooms. Connect the wires together directly and see what happens during the heating cycle. My guess here is the same condition will exist.

If so, then check for the amount of current both at the T-Stat wires and at the valve solenoids. Compare those readings to the other rooms where you have no problem. Same voltage readings means no problem.

Next place to check <if the voltage is the same> is voltage to the solenoids in the effected rooms in zone 5. Correct voltage there means you may have an inoperative primary valve, <first one in line> if the pipes are hot but the radiators aren't.

In referrence to the boilers cycling on and off every 5 minutes, it is most likely shuting off on it's high limit safety switch.

Raising the hot waters limit above the 160 degrees without any effects in zone 5, is most likely indicating it's not pruged of air, low on water or there is a flow restiction <Closed Valve> in that zone as discribed above.

Good Luck

TomBartco Enterprises.
Trade:Natural Gas Energy Consultant & Technician.
Appliance Service & Repairs Rep.
Vocations:Saw & Tool Sharpening. Small Engine Repairs.
Accurate Power Equipment Company.

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