Hot water baseboard system troubleshooting

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Old 01-18-10, 02:37 PM
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Hot water baseboard system troubleshooting

Hello;

I am trying to troubleshoot my firends hot water baseboard system. He has a residential NY Thermal boiler, running 5 zones for hot water baseboard heat and 3 zones running the in floor heating.

The in floor heating system has a zone valve off the furnace which controls hot water to a'hot water heater' storage tank arrangement, then to an additional circulator pump then to the 3 zones which control the various in floor heating locations. The 'hot water heater' tank is set at 100 degees C, therefore that is when this zone valve is commanded open. (seems to be a wierd system...but anyway)...

His pressure is at "0" until one of the zones is commanded on...then it rises to maybe 5 psi. We bled all the air out of the system...(not too much air present), and I found a couple of his contact switches in the zone valves were unservicable.

System temperature is normal...160 to 180...and all the aquastat setting appear to be normal as well.

I figured that since the bad end switches didn't command the aquastat 'on', then the open valve would allow the pressure to bleed off until a good valve and end switch operated, allowing the pressure to build up.

I changed the end switches but did not rectify the problem..

After bumping up the pressure to 15 psi, we turned all the zones on and the system worked nicely, however once all zones were 'off' the pressure slowly dropped to zero again.

He has one of those old style expansion tanks...the long steel ones with the valve on the bottom. I am not sure how these old ones workk so I was reluctant to open the valve....however I DID feel the bottom of the tank and it was 'cool' to the touch....if that helps at all.

Also, the second circulator pump runs ALL the time, even when all zone valves are 'off' and you are not demanding any heat. Is this normal for this type of system ?

the first circulator pump...for the 5 baseboard heaters, runs only when a zone is commanded on.

Any information will help

Thanks.
 
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Old 01-18-10, 03:09 PM
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Give us the simultaneous pressure and temp readings for the two conditions:

a. When the system is completely up to temp, all eight zones are calling for heat, and all the baseboards and floors zones are hot. (That will be the highest pressure the system will normally see.)

b. When the entire system, including the boiler, is cooled down to 100 deg F or below. That will be the lowest normal pressure - figure about 12-15 psi for a 2-storey house with the boiler in the basement.

Leave the expansion tank alone for the time being. There is no reason to suspect a problem there, at least yet.
 
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Old 01-18-10, 03:20 PM
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Hello again;

WHen the system is up to temperature with all zones running...he gets around 10psi. Once the zones close, and the boiler temperature cools, the pressure drops to around 0 to 2 psi @ 160 degrees.

When we bump the pressure up to 15 or even 20 psi....the system will run all day at that pressure as long as one of the zones is calling for heat....once the zone valves close (all) then the pressre bleeds off slowly toward '0'.
 
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Old 01-18-10, 03:58 PM
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Not good enough. When you raised the pressure, how did you do it?

Let everything cool down to less than 100 deg, check pressure. Raise it to 12-15 psi.

Then heat everything back up - boiler, piping, baseboards, floor, etc. With your hand, feel that everything is hot. Report back here with the pressure and temp. You may have to re-bleed the air.

I'm wondering how your pressure got so low. Has the system been open or drained for maintenace? Has this problem just cropped up? Is the shut-off valve open between the city water supply and the auto fill valve (a.k.a., pressure reducing valve)? If not, open it.

Something is haywire here, and I don't think it's the expansion tank.
 
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Old 01-18-10, 04:24 PM
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Hello Mike. I raised the pressure through the water fill valve.....(not sure of the tech term)...its the one with the little lever on top from the city water supply. I actually did let everything cool down, then jacked the psii up to 15...(it was around 2 psi when cool).

Once that was done, I started up all the zone valves and the pressure remained pretty stable until everything is turned off...all zone valves closed....thenn the pressure slowly bleeds off to below 5 psi.

Also...i spoke to my friend and he told me that he actually opened the valve on the bottom of the expansion tank and got a bunch of water and air....
 
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Old 01-18-10, 04:32 PM
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What you are describing sounds to me as though there may be a leak somewhere... If you bump the COLD pressure up, then heat the boiler, then let it cool again, it should return to where it was when you started... not continue to drop again...

3 zones running the in floor heating.
Are there valves on BOTH ends of each of the in floor zones? If so, close them and see if the pressure now holds... what type of 'in floor' are we talking about here? Copper or steel pipe in concrete slab? Plastic 'staple up' ?

There must be a pressure relief valve on the system, right? is it possibly piped somehow that you can't see the end of the pipe? i.e. outdoors... or to a floor drain... or something like that ?

NEVER trust a pressure gauge on an old boiler!
 
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Old 01-18-10, 04:48 PM
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Originally Posted by Mach7 View Post
Also...i spoke to my friend and he told me that he actually opened the valve on the bottom of the expansion tank and got a bunch of water and air....
Bad move. It just proved the obvious and possibly screwed up the expansion tank's charge.

There is likely a B&G airtrol tank fitting on the bottom inlet to the tank to check the water/air level.

As Trooper posted, maybe there is a leak?
 
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Old 01-18-10, 05:17 PM
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I am thinking he probably has a number of problems. It appears to me the system has never been 'maintained'. Anyway, I will tell him to make a service call...I will post back when the problem is fixed.

Thanks guys

-Jim
 
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Old 01-19-10, 03:41 AM
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I am thinking he probably has a number of problems. Anyway, I will tell him to make a service call...I will post back when the problem is fixed.

Thanks guys

-Jim
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