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Thread: Polaris hot water heater cycling often

  1. #1
    DIY Junior Member renrag's Avatar
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    Default Polaris hot water heater cycling often

    I read with interest cloves, ballvalve, and other comments in the HVAC thread on using polaris hot water heater for both dhw and radiant heat system. I installed a polaris last January and it provides hotwater for both my heating system and my dhw needs. I have three zones, two mixing valves(one for the cement floor zone). My system is 1/2 PEX with steel defuser plates under the upstairs floor. The system seems to work well, although I haven't had the upstairs heat on during a 30 below stretch yet. Anyway, my only concern is my polaris fires up almost every 15 minutes, runs for about 30 seconds and then shuts off. It did this all summer when there was no demand for radiant heat. My question is: Is this normal, if not, what should I do to keep the water heater from cycling so often? I am worried about burning out the igniter or other parts of the hot water heater control system. Just for your information, the heater runs fine when there is a demand on it, either for heating or dhw use. It seems like it cycles often only during the periods when there is no demand.

    Any help would be appreciated.

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    Does the unit have a differential setting adjustment? (i.e., a settable min/max value). If it does, and it is small, it may need to run often to keep it at the exact value programmed in. If it is adjustable, try making the min/max differential bigger. Then, if you don't have the pipes insulated, add some of that, too between the tank and the areas that are for heating.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3
    General Engineering Contractor ballvalve's Avatar
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    The Polaris has a fantastic recovery rate and high BTU input.

    I keep mine set at about 118 to 120 degrees. You can shower for hours if you so please because it keeps up with anything.

    You may not have heat traps on the system and you may well have passive recirculating of the water when the pumps are off. Thus the run time. If you have a passive system, you need a good spring loaded check valve. A polaris can be massive insulated like a electric unit as it has no top hot gas vent port. Pile on all your winter jackets, make sure your outlet has a big goose neck and traps, and insulate the first many feet of ALL pipe heavily.

    Mine ran too much at first with poor ignition, and by extending the short vent by 20+ feet, extended the run time [negative pressure gas valve that seems to reduce btu output with length of exhaust run.] and cured all ignition issues.

    Check your check valve, they LOVE to get stuck open with a bit of rubber washer or debris.

  4. #4
    DIY Junior Member renrag's Avatar
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    Default thanks ball valve, and jadnashua

    Where do I put the check valve(s) and heat trap(s). Obviously I feed both my dhw system and my radiant floor system with the heater. The heater does have two discharge ports to handle each system. If I put in check valves, do I need to have pressure tank(s). Right now I just use the pressure tank on the inflow system. I'll go back and look at your diagrams in the HVAC section but I don't think any of them exactly fit my situation. Many thanks for the help tweaking my system.

    renrag

  5. #5
    DIY Junior Member renrag's Avatar
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    Ballvalve.....I think I now know why the heater is cycling so much. This A.M. I turned off my radiant system via the valves between the system and the hot water heater port for heating system( the heater has a separate discharge port for dhw). I left the dhw port on. The heater has not fired up for over an hour now, so I figure the radiant system is siphoning hot water from the hot water heater on a continual basis. Not sure how to correct that, if I put a check valve in the line between the heater and the radiant system, will that keep the radiant system from siphoning hot water out of the hot water heater. That would be a relatively easy fix so I figure that can't be it. Thanks in advance.

  6. #6
    General Engineering Contractor ballvalve's Avatar
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    I am surprised the system has worked at all without a check valve from day one. The check valve sends cold water thru all the zones in summer and warm in the winter. It has to be placed correctly.

    And of top quality. I'll add some links momentarily.

    These guys have the idea but poor and over complicated execution. I use pex and ready made manifolds. mainly check their drawing showing the "N" location of the check valve.

    http://www.radiantec.com/pdf/Direct_...ing_System.pdf

    This is a 69$ check valve and I use a lot of them. Smoothest and quickest closing in the world.

    http://www.surpluscenter.com/item.as...&catname=water

    Put unions on it for maintenance. And turn the temp down and pile on the blankets.
    Last edited by ballvalve; 10-27-2011 at 09:47 AM.

  7. #7
    DIY Junior Member renrag's Avatar
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    ballvalve,

    thanks so much. A quick trip to the hardware store yesterday, came home and installed 1.25 inch check valve in radiant heat system feed line. Fired up the system and it works fine now, the heater only kicks on after significant demand, not every 15 minutes like before. Big thank you.

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