No heat in 2nd floor zone

Robw · March 2010

I just bought this house about two months ago. It has four zones one of which was done about two years ago. The original boiler was replaced in 2005. There have been problems with an upstairs zone since we bought the house. 

 

When the temperature gets down to the 20’s the upstairs zone will stop getting circulation. I can purge the system and shut two zones off and it will get working again. Then a few days later it will stop circulating again. I can repeat the above to get it going again.

 

I heard from the gas company who has the repair contract ( they do not work on anything connected with water) that that system has had trouble ever since the fourth zone was added for an addition. It does not appear to get air in the system. Would it be possible that when several zones open at once the pump is not powerful enough to pump the higher second floor?

 

Also the addition has radiant heat under the tiles, I don’t know what is buried in the floors, but there are two manifolds, return and supply of ¾ black iron with three rubber hoses of 5/8 id to each. They look like car radiator hose, I do not know if that is used under the tile. The straight heat that goes to all zones goes there also.

 

Any ideas for a solution? I have had a few heating people look at it but only got vague answers on what is wrong with it.

Robw · March 2010

Pictures

Pictures for no heat post

Robw · March 2010

Picture

I am new at this!

JStar · March 2010

Pressure.

What does the pressure gauge say for PSI? If you have your own water pressure gauge, that would be a better more accurate number.

I also think, without doing too much math, that the pump on the return, along with the 1" pipe supplying four 3/4" loops is killing your pressure and flow, so the water just doesn't have enough pressure to make it upstairs.

Robw · March 2010

pressure

I will get a gauge tomorrow and check it. Do you mean put gage on one of the Boiler drains above the zone valve?

Thanks

TonyS · March 2010

Are all four zone valves

on 1- 40 va transformer?

CMadatMe · March 2010

Your Solution

Click under find a pro and find a pro. From the pics posted I see no water mixing device for the radiant and no separate pump for the radiant. Looks like someone came in and just cut out the old boiler and slid the new one in.

You need to have a heat loss done for starters and that boiler needs to be re-pipied and cleaned-up. Get that circ off the return. You state that only when the temp drops below 20 that the pump does not run. Makes no sense. I can see that maybe when all the zones are open and running you may have some problems. That radiant is most likely eating up all the head of the pump. You could go for the simple possible solution and change the pump out to a Grundfoss UPS15-58 and put it on speed 3 but I would do some math and a little investigating into that radiant zone.

Is that a AWI-128 Crown boiler? If so it's DOE is 105,000. That header pipe size may be hurting you are far as flow rate and btu delivery but without a heat loss can't anwser that. Pressure has nothing to do with this so don't waste your time with a gauge. Heating systems work at 12lbs and the feed valve would keep feeding if you were not maintaning. Just check the boiler pressure gauge to make sure you are around 12lbs. What writing is on that radiant tubing?

JStar · March 2010

Experiment.

Can someone here make a drawing that shows the pressure and flow in each part of this boiler? I'm going to try to do it myself, and I'd like to know that I'm fully understanding why this particular piping job is wrong.

TonyS · March 2010

From what I can see

You have four taco zone valves on 1- 40 va transformer. That not enough. Open all four valves manually and see if you get flow. That may be the cause of your intermittent problem but as Chris pointed out , you have a lot more to consider.

JStar · March 2010

Pressure.

By checking the pressure, won't that rule out a faulty PRV?

JStar · March 2010

Learning.

Let's say, for the sake of my own understanding, that all the piping in this system created more than 28 feet of head. Then the 12 psi system pressure wouldn't be enough to overcome that, right? But if you pump on the supply, you'd be adding to the feed pressure. If you use a "standard" Taco 007 pump, moving 16 gpm at 5 feet of head, you'd have a 2 psi delta-P, giving you a total of 14 psi (32 feet of head) going to the header?

All of this depends on the size of the loops to determine head? Is it typical to see a system like this one where a 12 psi fill pressure isn't enough?

TonyS · March 2010

Jstar

The static fill pressure of a system is for one thing, to lift the water to the top height of the system...1 pound of pressure will lift water 2.31 feet. 12 lbs is usually enough for most heating systems. It has nothing to do with pump pressures or flow.

JStar · March 2010

Okay.

I understand that 12 psi will lift water to the height of a two-story house. But doesn't friction and equivalent pipe length affect what pressure the system needs to run at?

Robw · March 2010

Tested pressure

I put a gauge on the system it showed 8 pounds while it was running. I raised it with the makeup water to 15 it seems to be holding 14 with all the zones running.

I don't know what the pipes are made out of Copper, pex etc. I know the hoses coming out are car radiator types. This house has a another set of under concrete radiant heat pipes that were there from the begining (35) years.

The boiler is a crown AWI162SNST1PSU output 132,000

installed in 2005

I did not own the house when any of this work was done.

JStar · March 2010

Gauge.

Where did you attach the gauge?

Robw · March 2010

gauge

I put it on the zone purge valve on the troublesome zone. I left the valve open of course.

TonyS · March 2010

It effects the head pressure

that the pump needs to create,but doesnt effect the static fill pressure.

CMadatMe · March 2010

Header Piping

Is too small. 1" copper max flow rate is 9GPM ala 90,000 btu's on a 20 degree delta-t. You need to know how much tubing is in that floor to calculate head as the radiant is going to have the highest head. Other than flow you most likely are experiencing that you cannot deliver enough btu's to satifify the load. Do a heat loss and break it out by zone to see if that 90K will do the job.

Also check the circ and make sure that no junk has built up inside it. Why? Because you don't know if you may be experiencing some oxygen diffusion from that radiant thus obstructing the circor or worse there is a small leak in the tubing.

JStar · March 2010

Gotcha.

I think that's where I was getting hung up. Static pressure is only used to lift water initially to the highest point in the system.

CMadatMe · March 2010

You don't calculate all the pipe

when figuring head. You count the longest run. If the pump can overcome the longest it can overcome all. Rule of thumb formula for head. Longest loop/zone (this means from the circ back to the circ) x 1.5 x .04 = Head.

100ft x 1.5 x .04 = 6' head

JStar · March 2010

I think it makes sense now.

I was thinking of head pressure in the same manner as flow. In my head, I kept seeing each loop subtract from that sum total of pump head. And that's completely wrong, right?

I think I just needed to hear the same idea in a couple of different ways.

CMadatMe · March 2010

JStar

Here is an example of what you are looking for and this is all based on everyday design formulas and sizing based on a 20 degree delta-t, 0 degrees outside and 70 indoors.

Total Heat Loss is 50,000 btu's and there are 3 zones.

Zone 1 = 25,000 btus

Zone 2= 15,000 btus

Zone 3 = 10,000 btus'

To find flow rates use the following formula.

8.33 x 60 x Delta-t divided by btu = gpm

8.33 x 60 x 20 divded by 50,000 = 5gpm total system flow rate. Do the same for the zones. Z1 = 2.5gpm , Z2 = 1.5gpm , Z3 = 1gpm. Now my longest zone is 150' so using the formula I previously gave you my head is 9'. I need a pump that can move 5gpm @ 9' head to deliver the required btu at design conditions. Which by the way can been done with a Taco 005 or a Grundfoss 15-58 on speed 1.

Now to figure out my length of baseboard for the zones I need the baseboard chart (that 90 percent don't use) to calculate the require total length needed from my heat loss (which again 90 percent don't do). Let's say zone 1 is one big room. So I pull out the chart and only see a 1GPM and a 4GPM rating but also on the chart are water flow correction factors. I take the baseboards rating at 1GPM and I multiply that by the proper correction gpm based on my zones flow rate. In this case we will use Suntemp 700 Series. At 180 degree water and a 1GPM flow rate it puts out 560 btu's a foot. So I find the 2.5 on the correction chart (1.038) and do this. 560 x 1.038 = 581 btu's a foot. So I need at the minimum 43' of baseboard to heat this space to 70 degrees at at my outdoor design of 0 degrees.

Hope this helps

Slimpickins · March 2010

Lotta issues

From what I see it looks like your system has more issues than Reader's Digest. It sure looks like you may have Entran tubing, can you read anything on the tubing to verify? Running Entran at high temps will cause major problems even if it is the supposedly good Entran III. Then there is the oxygen issues with your cast iron boiler and components. Also no boiler protection, no mixing and from what I see on the manifold, it's not reverse return. It appears the first tube is getting all the flow.

You have more problems than pressure. You need a pro that is competent in all these issues. Where are you? At the top of the page click find a professional and get some help.

CMadatMe · March 2010

Yup Alot of Issues

The total system needs to be evaluated.

Robw · March 2010

pump runs

I did not make myself clear, I did not mean the pump doesn't run. What I meant was that the upstairs zone does not get heat in extreme cold weather. The other zones are OK. It seems when all the other zones start up the top zone is starved. It has been purged by everybody, air is not the problem.

Robw · March 2010

pump

I did not make myself clear, I did mean that the pump does not run when it is below 20. I meant that the second floor zone does not get circulation when the others turn on. The pump runs, but it starves the second floor. It has been purged by everybody and their brother, that is only a temporary fix.

CMadatMe · March 2010

Heat Loss Heat Loss Heat Loss

The 2nd floor is not starving because of the pump. It is likely moving water but not able to move the btu's required due to that header size off the boiler. That header looks like 1" copper is it not.

JStar · March 2010

My objective.

I understand how to design system piping and pump sizes based on the given data. What I've been contemplating today is a way to visualize how the pressures work together in a system. I have a hard time accepting data without fully understanding everything about a system. The math needs to make sense in my head.

Example: On a three zone boiler, you would size the pump for the longest run with the most head. I've been asking the question, what would the pressure be in the other zones and how is it affected by pump placement?

Zone 1 = 9 feet of head

Zone 2 = 6 feet of head

Zone 3 = 3 feet of head

So you pick a circulator that can overcome 9 feet of head (and whatever gpm you want). 9 feet of head = 3.8 psi Delta P. So...

Zone 1 = 3.8 psi Delta P

Zone 2 = 2.5

Zone 3 = 1.3

Now, if we put the circulator on the supply, after the tank, we'll have 15.8 psi after the pump. Now, since the 12 psi in the tank never changes. Can you find the pressure in the other zones by adding their delta P (converted from foot head) to 12?

Or...is every supply line seeing that same 15.8?

==========

If the pump is on the return, the pressure difference is still 3.8 psi, so the outlet is 13 psi and the suction is 9.2 psi. Using the Delta P's for the tree zones again, we're left with these pressures at the ends of each zone...

Zone 1 = 9.2

Zone 2 = 10.5

Zone 3 = 11.7

This is where I'd like some feedback so I can straighten out my thinking and be able to use this as a method of troubleshooting. You could potentially determine the foot head of a zone by reading it's pressure.

CMadatMe · March 2010

This may help

you out JStar.

JStar · March 2010

I'll read through that. Thanks.

I think what I'm getting at here, is to be able to point at any part of the system and know exactly what numbers I will find there; pressures and temperatures. When I'm troubleshooting, I like to know the answer before I even ask the question.

For example: If a four zone boiler isn't getting enough heat in one zone, I should be able to put a pressure gauge and surface thermometer on the supply and return of that zone and know what to expect in a working, properly balanced system. Let's say there's an isolation valve or zone valve tucked away in a drop ceiling that I haven't seen yet. Or maybe somebody renovated a part of the house and replaced some baseboard with 1/2" PEX. Who knows? So if I go to a house one day and see a certain pressure on a zone, and I go back the next day and find a higher pressure on that same zone, I'll know that some form of resistance has changed in that line.

I hope this all makes sense. I need to go run a bath and think about this a bit more.

No heat in 2nd floor zone

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