No circulation to top floor

zepfan

I have a customer with a three zone HW baseboard system. I have serviced the oil burner on it for the last five years and not had an issue with the water side, until today. 

There is no heat to the top level, the basement, and main level are fine. When I first got there I thought it may be a power head, but the valve open, and closes fine, and it’s end switch starts the circulator.

I purged the air from the zone with the isolation valves and boiler drain, as there was some air in the circuit. I noticed when I started that with the circulator off, and the isolation valve close there was 0 psi in the top level circuit, after purging any air, and adjusting the PRV, the circuit showed the same as the boiler, right at 18 psi. The top level is about 22 ft above the boiler, so I would think 18 psi should do it. The length of the loop is about 45 ft. 

After about 15 minutes of the burner running, the water going to the top level was 150 degrees , the pipe coming back from the top level was 85. 

The only thing that I can think of is maybe the taco circulator 007-F5 may be wearing out, and not be able to push the water through the loop. Any suggestions would be much appreciated. Thanks to all

EdTheHeaterMan

One circulator for the 3 zones? I assume yes.
So that we understand the way a closed hot water systems operates... The pump does not need to be very strong because it is not lifting the water up 22 ft in the air. It is just circulating that water that is already up there. The weight of the water coming down the return pipe offsets the weight of the water going up the supply pipe.

That assumes that there is no air in the loop. If there is air, then the pump is not strong enough to lift the water more than about 1 foot higher in the supply, than the level of the water in the return.

So I believe you have air in the upper third floor zone.

EdTheHeaterMan

You should have at least 3 to 4 PSI more pressure in the system that what is required to lift the water 22 feet high. the extra pressure is to insure there is enough pressure for venting the air out of the zone. Since a column of water 28" high will exert one pound per square inch of pressure at the bottom of the column then it makes sense that 12 pounds of pressure per square inch at the bottom of the system will lift the water 28 feet in above the gauge location. Here is a graphic I used to illustrate this fact in order to get the water to push the air down from the third floor, you will need to get the water pressure up to over 25 PSI in order to entrain the air on the way down. Just a mild pressure of 15 to 18 PSI may leave air in the top loop.

EdTheHeaterMan

Once you FLUSH the water thru the third floor to force all the air out, then you can return the system pressure back to about 15 to 18 PSI. If the Circulator pump is working fine on the lower floor zones, then it should work just fine on the third floor zone.

Is the expansion tank in good working order?
Is it the pre-charged type or the big, old type that is strapped up between the basement rafters above the boiler?
Where is it connected to the system?.

zepfan

thank to all that responded. The pump is on, and running drawing FLA, so I was skeptical that it was the issue. The expansion tank is a conventional type that is piped in near the water outlet of the boiler. It was isolated from the system and drained less then a week ago. Yes one pump for all three zones

EdTheHeaterMan

zepfan said:

thank to all that responded. The pump is on, and running drawing FLA, so I was skeptical that it was the issue. The expansion tank is a conventional type that is piped in near the water outlet of the boiler. It was isolated from the system and drained less then a week ago. Yes one pump for all three zones

Is the water outlet on the supply or the return?
Is the water outlet closer to the circulator inlet or closer to the circulator outlet?
Is the water outlet actually the water feed with a pressure reducing valve to feed water into the boiler from the house water pressure?
Is the water outlet labeled "Supply" on most boiler piping diagrams?

hot_rod

If you have a "conventional" steel compression type tank above the boiler, then you don't want any auto air vents or air purgers.

If it is a small diaphragm type, connect it at the bottom of the fill valve along with the fill valve.

HomerJSmith

Well, interesting. If the sys worked properly before, then what has changed. If you think you have air in the top flr circuit how did it get there?

A delta T between 150 deg input and 85 deg return means to me one of two things. You have a lot of heat emitters on the top flr or you don't have the flow thru the top flr circuit. If it worked before, I go with the flow issue. Why a flow issue? Rounding up the usual suspects, the pump, the ZV, a restriction in the circuit (a partially closed valve), air in the circuit.

The pump: Taco pumps have cartridge in them. I have cut those cartridges apart on more than one occasion and have found that the interior was filled with black granules that prevented the rotor from turning or slowed the rotation substantially. It may be a situation of where the lower flrs get the circulation but the top flr lacks the head necessary for the rated flow.

The ZV: I would certainly want to confirm that the ZV is really functioning and opening all the way. That the voltage is sufficient to open the valve, etc.

Restrictions: Make sure all the valves, isolation and otherwise, are fully open.

Air: Make sure the circuit is air free. You need a flow of about 2ft/sec to move air down a vert pipe.

I think I would concentrate on the pump and the ZV.

leonz

zepfan said:

thank to all that responded. The pump is on, and running drawing FLA, so I was skeptical that it was the issue. The expansion tank is a conventional type that is piped in near the water outlet of the boiler. It was isolated from the system and drained less then a week ago. Yes one pump for all three zones

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Please upload a picture or two or three of the expansion tank, its piping and the air scoop.

You mentioned that the tank was isolated and the water was drained from it a couple of weeks ago.
If it is a horizontal steel compression tank it was waterlogged and it lost its point of pressure change.

You cannot use a steel compression tank and a microbubble absorber or automatic air vents together with a steel compression tank as they will allow all the air in the steel compression tank to escape and your circulator will lose its point of no pressure change and not work or bare work at all and burn up eventually.

If it is a vertical expansion tank an extrol tank for the example and you isolated and drained water from it you may have a tear in the bladder and the tank became waterlogged and you lost the point of pressure change and the expansion tank does not have the correct air pressure charge and need to be replaced.

Did you isolate the basement and first floor(shut them off) turn the thermostat all way up on the third floor and just let the circulator runt to push the water through the second floor??

Air there air bleeders on the 2nd floor piping or radiators??

Lastly please explain FLA.

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NOW with that said:

if you have a beautiful steel compression tank hanging in the basement ceiling joists you will need to cap the microbubble absorber and close it tight to stop it from working and do the same thing to any automatic air vents in the system to prevent air loss.

You need to go back and drain the water from the steel compression tank and when you have nothing but air stop!!!.

zepfan

Thanks to all that responded. It appears the issue was a faulty circulator that once we changed all appears well. FLA - Full load Amps. With the corrected applied voltage and the pump drawing right at FLA I made the assumption that the circulator was doing all it could. But once removed from the system debris was noticed in the housing so I guess that was slowing the flow of water through it. The circulator was 30 years old so I think this was stuff that had built up over time. Thanks to all