Hot water loop on steam boiler

Bob_43

I believe its 3/4 copper. I still think the 1/2 pipe is the path oleast resistance. It should still be easier for the water to pass through the pipe than the boiler. This is where you ask Dan or the other pro's for their opinion.

Best thing to do is post a picture for these guys to look at the piping.

John Doll

Installation question

My contractor is coming out today to hopefully resolve an issue we have with bubbling noise and knocking on a hot water loop recently installed on our steam boiler. I sent them copies of the pages from Dan's homeowners guide that seemed to indicate the problem was high water temperature. The guide has a diagram that shows a hot water loop as the fix. Are there any other things I should look out for or discuss with the contractor prior to starting the work?

Unknown

Here's some info, from the Library

http://www.heatinghelp.com/pdfs/346.pdf

Noel

Bob_43

I have the same problem at my house. To fix my problem, I needed to adjust the valve that mixes the return water from the loop and the water from the boiler.

If the water is to hot, you get banging noises. I ended up buying a temp gauge and I try to mix the water to 100-110 degrees. This seems to limit the amount of banging. I usually need to do this 2 times a year. Early in the heating system when the system isn't on all the time and mid winter when I am in full heating season.

Hope this helps.

Steve_126

How are you able to heat the zone with the water blended to only 110 degrees? I have a similar issue and had the installer pipe in a bypass line as well. What I don't understand is why the supply water is reading about 170-180 degrees but I still hear the noise of water banging through the pipes. How could it be flashing to steam at such a low temp? For a second story zone from the basement (10 foot ceilings) what is the appropriate temp of the water to eliminate the possibility of water flashing to steam but also effectivekly heat the zone?

Bob_43

I'm just a Home Owner, but it has to do with the water flow, length of baseboard, and heat loss. Most of the charts list water temps from 140 - 220. I was surprised how much heat 110 degree water can produce.

I can run a higher temp, but I get a lot of noise if I do that. I have found between 100-110 to be the sweet spot for my system. The only differnce that I have seen is that the pump needs to run a little longer to heat the room. The room heats great even at the lower temp.

Try this, when the system is banging, play with the valve that mixes the water(bypass valve). If you slightly open the valve(lowering the temp), your noise will probably go away. I still have no clue what causes it.

Steve_126

Have you read this doc? It was helpful for me.

http://www.heatinghelp.com/heating_howcome6.cfm

Bob_43

Yes I have. That is how mine is piped. I did not do the piping, I had my steam guy do it following the diagram. The valve I was talking about is at the bottom of the picture. It controls how much water from the loop is mixed with the water from Boiler. Is yours fully closed?

Hopefully someone will tell us what the noise is from.

schiller

copper expands w/ temp. the hoter the water the faster and greater the expansion, this is what causes the banging and poping, you want to look at all the points where the copper comes into contact the building. you might be able to adjust a hanger to releave the pressure. I was at an elderly ladys house just the other day and she put wax paper between pipe and the floor where it was rubing and stated that her husband did this and it always solved the problem, he dead now so he must be right, the point is copper expands if it can expand w/ out touching any thing it will do so quietly.
good luck

schiller

sorry I got side tracked durning my last post, you should also check in side the base board where the fin tube is supported by small metal brackets, those brackets should have some type plastic clip or race that allows the copper to move smoothly when it expands.
T

John Doll

Hot water loop on steam boiler

Do you need to adjust the valve on the loop and the valves coming out of the boiler? The loop seems to be working now, but I had fully open the valve on the bypass and throttle the valves in/out of the boiler to half way open. Fortunately for putting up holiday decorations but unfortanetly for testing your heating system, we have had very mild weather so I can't tell if the room will warm with the boiler valves turned that far off.

Bob_43

Mine is the opposite. I throttle with the bypass valve and the other 2 valves are wide open. I believe you are supposed to use the bypass to mix the water. The way you are discribing it, I think you are just slowing down the flow.

From's Dan's Q and A

Q: Well then, how can I make sure the water at the top of the top of my system never flashes into steam?

A: By making sure the water entering the zone never approaches 212 degrees F. The simplest way to do this is to blend a portion of the water that's already been through the zone with the hot supply water leaving the boiler.

Q: Do I need special valves to do the mixing?

A: Not at all. All you need is a 3/4" copper line between the zone return and the inlet side of the circulator, a 3/4", full-port ball valve and a thermometer. Pipe the ball valve into the bypass line and leave it fully open when you first fire the steam boiler. Next, let the boiler come up to steam pressure, and then start your circulator. With the bypass ball valve fully open, nearly all the water in the zone will bypass the boiler because it's easier to go through the bypass than it is to go through the boiler. That's the path of least resistance. Now, to make the water flowing into the zone hotter, all you have to do is throttle the bypass ball valve a bit. Keep you eye on the thermometer as you do this. You'll see the temperature rise very quickly.

Long Beach Ed

Water Flashing to Steam

In addition to the clanking and popping of expanding and contracting copper, steam could indeed be a problem.

You see, in a vacuum, water boils at a very low temperature. Each time that circulator comes on it reduces the pressure in the baseboard loop. If it's reduced enough, for even a second, the hot water can flash to steam. That steam takes 1700 times the space of the hot water it replaced.

Wat happens is this expanding medium pounds the pipes and fittings. It also bashes up the inside of the pump.

So keepting the mixture down around 130 - 160 degrees wouldn't be a bad idea. If it would heat the space or not depends on how much radiation was installed in the room. The designer, we hope, had a temperature in mind when he installed it to provide enough heat on a zero or 10 degree day.

Long Beach Ed

John Doll

Thanks - I think I figured out the issue. My installer did not read the fine print. My bypass line and the loop are both 1/2". It seems that without the 3/4" bypass there is no "path of least resistance". Is you bypass line made from large pipe?

Unknown

I would install an aquastat controller & a temp gauge. The aquastat would prevent the circ from running when the water temp is too high. Don't forget your spring check valves.

John Doll

The Aquastat

An Aquastat is installed. However, it doesn't cut off the circulation if the water is too hot. It fires the burners to heat water (not enough to produce steam) if the thermostat on the loop is calling fro heat and the boiler is not hot. Can it do both?

Unknown

I'll try again, John.

http://www.heatinghelp.com/pdfs/346.pdf

Noel

Unknown

Did you forget to put in the silver goop ( a technical term, lol) in the emmersion well ? The aquastat will not work proper without it, & even with the paste in there you should adjust it by what your gauge tells you.

brucewo1b

John the aquastat

is only there to make hot water when the steam zone is not calling, you need the bypass to temper the water for when the steam zone is running and the water loop calls too.

John Doll

Pictures of Installation

I have attached pictures of the installation. The things that I can identify that are not consistent with the detailed instructions are the location of the pump and the size of the bypass line. The pump is in between the bypass line and the boiler and the bypass is equally sized with the hot water loop piping. I was able to reduce the termperature enough to eliminate the flashing to steam in the hot water loop. But, I had to fully open the bypass line and throttle the bioler return back to 50% to accomplish this. It works, but it seems like there is a wierd running water noise in the hot water loop. I can hear it in the base board and in the walls wer the pipes run to the addition. IS this normal? Should I have the installation of the bypass loop corrected?

John Doll

Thanks

Noel - I did look at your original posting and shared it with the tech. Unfortantely, he still did it differently. Can you take a look at the pictures I posted and let me know if it is a big problem?

Unknown

It needs to be repiped.

It's trying to pump vapor, and that's a problem.

Noel

John Doll

Thanks Again

That is what I thought. Is the issue that the pump is on the wrong side of the bypass or that the bypass is not larger than the other piping in the hot water loop (and therefore not he path of least resistance) or both?

Unknown

Both