hot water heating system

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  #1  
Old 01-19-04, 05:30 PM
makerstner
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hot water heating system

I have a separate gas fired hot water furnace that goes to the second floor of a two-family.
The convectors are built into the walls each with an individual loop.
Some of the individual loops do not get hot on the second floor;
they do get very hot in the basement where they brach off.

I have tried bleeding them, and although water comes out, the hot water does not come up.

The system currently has pressure of about 20.

Any suggestions??
 
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  #2  
Old 01-19-04, 05:38 PM
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When you say that each convector has an individual loop, do you mean that both pipes to each convector come off of the same pipe in the basement? Or are there two larger pipes going around the basement to feed the convectors?
 
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Old 01-19-04, 05:41 PM
makerstner
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yes, both the supply and return come off they same pipe in the basement
 
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Old 01-19-04, 05:48 PM
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You wont believe this BUT, ...

move the pumps to the supply side and watch out! You'll get heat like you won't believe.... the secret is to pump away from the point of no pressure change. This point is typically where the water make-up is between the expantion tank and the air scoop. If it isn't... make it that way....all the bleeding and air problems will disappear. The heat will be there in a flash.
All to many times ,plumbers, not knowing any better, find the pump attached to the return side of the boiler think this is where it should go... Where in reallity, it's placed there for shipping purposes. In a nut shell...The fix is to put the pump on the supply side. If you need a specific with diagrams on this project,... go to heatinghelp.com , the book is entitled Pumping Away. All HVAC people should read it. It also has primary and secondary pumping.

 
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Old 01-19-04, 06:12 PM
makerstner
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There is only one pump and it is located between the furnace and the expansion tank on the supply side
 
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Old 01-19-04, 07:24 PM
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Your system would use venturi tees and there is only so much push that they can develop. If 1/2" pipes were used to plumb the convectors, be sure there is no place where the pipe could have an air trap. Many times contractors used soft copper and if the pipe does not pitch up all the way from the tee on the main to the convector, air can get trapped and prevent circulation. When you open the bleeder on the convector, there is no way to get trapped air out unless it has reached the convector. You should also check the tees at the main to be sure they are in fact venturi tees. One will be a venturi and the other will be a regular tee for each convector. There should be some markings on the venturi tee. Like an arrow or the word supply. It may have a tag that says Monoflo too. If both tees are regular copper tees, then that would be the problem.
 
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Old 01-19-04, 07:28 PM
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pumping away

Think about this for a second...when the circulator starts and it creates a negative pressure behind it, the water pressure will drop, this will cause the water supply to add water unless its already overfilled, then it will drop about 7 #, the outlet side will be positive @12PSI (the tank pressure), thus your pump differential that causes the water to move from higher pressure to lower pressure. You have and expantion tank AFTER the pump...why should the water go uphill against gravity when it can compress the expansion tank at a lower pressure?(The path of least resistance)and its here where you will loose some of the pumps energy, into the expansion tank, refered to as the point of no pressure change
On the other hand, if the pump was forward of the expantion tank, there would be no drop in pressure because the expansion tank will maintain the pressure at 12PSI (the common set point for two story, and the point of no pressure change) and use all of it 6 PSI differential towards increasing the pipe pressure and compress any air into the water, much like when a coke has the top on, the bubles are in the liquid till you release it by lowering the pressure (removing the bottle cap), and so the water pressure increase forces it to go to a lower pressure (upstairs plumbing)....
Move the pump!
 
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Old 01-20-04, 07:31 AM
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Or move the expansion tank. It may be easier to pick a new location for the tapping of the expansion tank. Perhaps you could add a tee where the relief valve now comes off of the boiler and add the tank, and put the relief valve back there too. It i sprobably easier than re-piping the circulator. I'm not sure this would solve the problem you started with but hvac is right about the principles of pump operation in a closed hydronic system.

In the case of venturi system the only differential you have is developed by the venturi itself so more system pressure would not help the circulation. Air removal is helpful anytime you can get it. Water velocity helps in the case of the venturi and you probably won't increase that without changing the circulator. What you really need to know is that you have a venturi tee on the convectors that aren't working and if there could be air trapped somewhere in there.
 
  #9  
Old 01-20-04, 03:51 PM
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zones

how many zones? if you have an indirect water heater, it should have it's own circulator and aquastat. We need to know is this a series loop? If you have two loops you should have a ball valve or butterfly valve to balance the zones.... have a way to redirect the water to another zone (balance). Or does it just go in a circle...in one side of the baseboard, and out the other... If the supply has a tee riser and comes back into the same pipe usually within 6" of the other tee...most use monoflo tees on both ends when the baseboard is above the travel of the heating line...moving the pump solves problems many monoflos have also...like noise.
 
  #10  
Old 01-20-04, 05:45 PM
makerstner
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I found out that my this is a diverter tee system and I have only owned the house 2 years so I am not sure it is a cronic problem or one that always exsisted.

There are diverter tees in place but they are the first tee in the loop and in some cases where there is more than one radiator, the supplies seem to be back to back with a separate diverter tee one after another with the returns having a normal tee back to back.

As far as relocaing the pump, it is enclosed in the furnace .

I suppose I could relocate the expansion tank on the return line prior to entering the furnace
 
  #11  
Old 01-21-04, 02:13 PM
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moving the tank

You might get away with moving the tank to the return side as long as yo have only one pump. And the hot boiler pressure stays below 23PSI...because the pump pressure will be added to the static pressure of the supply line and if it hits 30...you safety relief will pop. If you have two zones and the tank is on one zone, the zone with the tank wont heat if both are calling.
PS... you have a boiler not a furnace, and it must do the whole house, because you said it does the basement as well, or am I missing something???
 
  #12  
Old 01-23-04, 08:15 PM
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Hot water Heating System

Zone Valves are an antedated of doing a system. Suggest you change to a more modern way.
Take all your zone valves off,
replace all your rad valves with Thermostatic valves and fit a differential valve at the end of the line some were.
Let the TRV's control the temperature in each space separately and the differential valve will take care of any dead ending of the pump if all the trv's just should happen to close at the same time.
It makes no difference whether the pump is on the return or the flow but the expansion tank and cold feed inlet should be at a dead spot. And if the pump is on the return then the connection to the expansion tank should between the pump and the boiler. The expansion tank connection MUST have a heat loop to prevent any hot water getting near the tank or it's life will be shorten.
I've always fitted pumps on the return with no problems if fact the couple times I fitted them on the flow I had more pains in the butt than I like to remember. In fact one I remember I had ever repeating problems with Air in the first radiator that I swore off pumps on the flow for ever. That was over 30 yrs ago now.
On a closed circuit the pump will push though the boiler and suck back from the radiators just as much as on the flow were it pushes into the rads and sucks back from the boiler. It's 6 of one and half a dozen of the other.
Of course on the flow you are more likely to get caviation in the pump and stuff up impellors because of the hotter water.
 
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Old 01-24-04, 05:12 AM
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I am surprised at your experience with pumps Narroc, I have been putting pumps on the supply side for about 10 years and seem to have less trouble than when they are on the return. Less problems with air too. I also never heard of the heat trap for the expansion tank but it makes a lot of sense. OK back to the topic.

It shouldn't matter drastically that the 2 diverter tees are near each other as long as the regular tee that corresponds to the diverter tee is at least 18 inches away and not on the other side of an elbow. Some replumbing may be in order.
 
  #14  
Old 01-24-04, 11:14 AM
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dead heading the pump

using TRV's is a great way to control individual zones but the circulator runs non-stop and should have a bypass loop with a differential pressure valve to allow the water to return without deadheading the pump.... the only problem is some people try to cheap it out without the valve, and it sends the full pump pressure back to the boiler and pops the safety relief. Or they use a line about3/8" and this velocity noise can transmit throughout the system.
The pressure differential valve is set to be closed when all zones are open and gradually opens to channel unused water back to the boiler when it senses an increase in pressure.
As far as hot water on the expantion tank degrading prematurely....Never heard of it, I've had mine in for 10 years and by boiler cuts out @ 205F.
 
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Old 01-24-04, 01:20 PM
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Hot water heating

I think I did mention that a differential valve should be fitted to prevent deadheading the pump.
Perhaps the problem you guys have so much problems with expansion tanks is that you don't fit a heat loop to them.
I've just done a home job wall hung boiler 10 rads, I couldn't fit a differential valve beacause all the pipe work was hidden so I fitted locksheild valve to the 2 bathroom rads so they can not be shut off so that there will always be a circulation though these rads, All the other rads had TRV's, also fitted a programmable thermostat to 1) allow the home owner time control and 2) as over ride to the system.
The system runs at 1 bar (15 psi) with the safety at 3bar (45psi) the pump has a head of qpprox 3/4 metres so it would be hard put to blow the safety.
We use the european equipment which all runs around the 1 bar mostly with safetys at 3 bar.
 
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Old 01-24-04, 09:01 PM
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circulator control

so the unit heat runs continuously pouring heat into the bathroom non-stop?
As far as the differential pressure valve....Sorry, I missed that.. But! If your X-tank is in front of the circulator, then you wont be able to increase the pressure on the supply side (the point of no pressure change)...only a drop of pressure on the return side of the circulator of a pound or two.....because the rest of the circulators energy will be absorbed into the diaphgram of the X-tank(point of no pressure change) ...usually 12PSI. This is also normally where the make-up water supply enters the picture.
By the way,... Pumping away on the supply side is the norm in Europe...the USA ,I thought, were the only ones doing things backwards...
 
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Old 01-24-04, 11:12 PM
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Hot water heating

Don't see your point about not be able to increase the pressure on the supply side, Why do you want to increase the prssure??
I've never had a problem with system circulation or air and been able to run on the design head of the pump mostly.if any thing occassionally too much circulation but slow the pump down to lo speed.
The pressure gauge hardly varies on the boiler gauge with pump on/off. As the water is going away from the boiler as fast as it is coming back to the boiler.
Help we only talking 1-2 metres head pressure Not 10-20 psi. The pointer may give a odd flick as the pump turns on but thats all.
As rule I like to have the bathrooms warmer than the rest of the house over here as most people wear less clothes in the bath room than the rest of the house and as a consequence feel colder with less clothes on.
 
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Old 01-25-04, 07:47 AM
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the bathroom

I agree that the bathroom should be the warmest with good reason...also...warmer air has the ability to hold alot more water vapor than colder air and is less likely to mold or mildew...it won't condence on walls as redily ect....I've actually unplugged my exhaust fan to the bathroom to try add some humidity to the space by leaving the door open, as I don't have a humidifier...this does a great job, it makes the house warmer (heat in the vapor) and actually raises the RH about 4 to 5%, and I'm not throwing heated air outside.
As for increasing the pump pressure...some places run fine with the pump on the return side,...many don't. People with diverter tee systems usually have air vents on the baseboards,...why?... because they are reknown for having air problems ...one reason is the turbulence and pressure drops release air into the system like a soda bottle releasing its pressure...the air comes out of suspension. If the velocity isn't strong enough to push them through they get trapped. If your using 12PSI in the system, and the boiler is in the basement and heating the top floor of a 2 story,... it may actually go into a vacuum when it starts, this is why we usually jack the pressure to 18 PSI when these problems are experienced. I had a museum that had field reps up the wha-zoo trying to get the air out of this hot water system puting in spiro vents everywhere...untill I moved the pumps to the supply side, it ran cold shortly after bleeding... I knew the pressure was low because I attached a gauge to the air bleeder vent It dropped from 3PSI to 0 or 1 PSI. I had the supply water up to 25PSI but the pressure safety was popping here and there. When I moved the pump to the supply side, it went up to 6PSI with the make-up set on 18PSI....never had to go back again...
 
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Old 01-25-04, 07:48 PM
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Hot water heating

Well you certainly were running quite a hi head pressure on your pump if it was pumping 6 psi. I would suspect that the perhaps the pump had a lot more head than it should have had or perhaps the pipe sizing was a bit on the small side. Or were the lockshield valves on the heaters shut down too much. This caused the pump to suck like mad to try and get the water back to the boiler.
yes I aggree it is very possible to suck air into a system.I've seen it suck air in though valve glands etc while these things don't leak water out and even though air ****s when the pump is running which is why I like to shut the pump off when airing. guess air is a lot thinner than water. lol,
Both the European Ferroli and the Immergas wall hung boilers have the pump on the return side and the X tank on the suction (inlet side of the pump).
If the pump pressure was that lo on the inlet side of the pump I would thinking that cavitation when the water got hot would be the next problem.
I've seen several pumps pack up from cavitation luckily (not my install) one had been fitted on the supply on a domestic secondary water supply.
Not only did it have cavitation, but when some one ran a bath the flow of water though the pump which over speeded it, but it burnt out the motor as well in to the bargain
 
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