Flow Control Valve or Zone Valve

[bug512]

Hello, I have a friend who has a oil fired water boiler with a tankless coil, single thermostat.
He states that the temperature in the house is sometimes greater then the setpoint on the thermostat.
I checked that the thermostat and pump control work properly. the adjustments on the aquastat are: 180 / 160 with a 10 differential.

One thing I noticed is that the system does not have a flow control valve or zone valve.

I guess the question is he has lived in this house for 15+ years and has never had a problem with gravity circulation, but now he does?

The supply is a single pipe off of the boiler, but there are two returns.

So my questions are:

Should I install a Flow Control Valve on the supply?

Should I install a Zone Valve? Two? on the returns?

Or?


Thanks in advance.

[Big Unit]

What would you valve off? The t-stat should be the main control in this situation. If you put a valve in their the valve will close with the boiler operating and that water will heat up like crazy and be tripping safety limits every time. Generally you would only use valves in this situation if you had multiple zones with multiple t-stats.

[bug512]

What would you valve off? The t-stat should be the main control in this situation. If you put a valve in their the valve will close with the boiler operating and that water will heat up like crazy and be tripping safety limits every time. Generally you would only use valves in this situation if you had multiple zones with multiple t-stats.

So are you telling me it is "normal" not to have either (flow control valve or zone valve) in a single zone system?

What prevents gravity circulation?

[lentz]

All of our Hot Water Boilers have a flow control valve weather they are zoned or not. Something has to stop that circulation of water when the pump is not running.

[trout lake]

It must be an old system. I love those older types. Are the pipes larger diameter black iron? I’ve worked on systems in a residential application that had 5 inch supply and return lines with branches coming off the mains. The older systems like that were based on straight gravity. No pumps. They worked like a hot damn. The problem with them was you needed to build a bigger house than you really wanted just to accommodate the piping J
To answer your question about valves and zones. You need to be able to control the flow of water. I assume from what you’ve described the stat fires the boiler directly without going through a zone valve. Is this correct? If it is the system will not be very precise as far as regulating your temp set points. The boiler will cycle to maintain the set point of the aqua stat. This you indicated was around 180F. With the boiler cycling and no zone to prevent circulation the water from the boiler will migrate through the system. In the old days, when they didn’t use zones, they had shut off on the rads. Every room could be adjusted through their own valving. If your friend doesn’t have this type of set up, he will have poor control of the system. He should have you or someone cut zone valves into the system. Zones vs. valves because throttling is a poor option. The main stat could be then run through the zone valve and the control point would be much better. This can be done with little expense. The system will need to be taken down to install the zone(s). When this happens also put isolation valves in so that in the event of mechanical failure, you can work on the system without loosing all the fluid.

[lentz]

If the house is only 15 years old I dought that it is a gravity system. We installed the gravity systems back in the 30's and 40's. Then we got those Sunny Day Crane boilers and the B & G circulators and every one wanted one. We would get truck loads of boilers at a time with the Petro oil burners.

[bug512]

It must be an old system. I love those older types. Are the pipes larger diameter black iron? I’ve worked on systems in a residential application that had 5 inch supply and return lines with branches coming off the mains. The older systems like that were based on straight gravity. No pumps. They worked like a hot damn. The problem with them was you needed to build a bigger house than you really wanted just to accommodate the piping J
To answer your question about valves and zones. You need to be able to control the flow of water. I assume from what you’ve described the stat fires the boiler directly without going through a zone valve. Is this correct? If it is the system will not be very precise as far as regulating your temp set points. The boiler will cycle to maintain the set point of the aqua stat. This you indicated was around 180F. With the boiler cycling and no zone to prevent circulation the water from the boiler will migrate through the system. In the old days, when they didn’t use zones, they had shut off on the rads. Every room could be adjusted through their own valving. If your friend doesn’t have this type of set up, he will have poor control of the system. He should have you or someone cut zone valves into the system. Zones vs. valves because throttling is a poor option. The main stat could be then run through the zone valve and the control point would be much better. This can be done with little expense. The system will need to be taken down to install the zone(s). When this happens also put isolation valves in so that in the event of mechanical failure, you can work on the system without loosing all the fluid.

No this is not the case at all, the house has a newer hot water baseboard system, if I would guess not older then fifteen years old.
The pipe leaving the boiler is maybe 1" copper.

[bug512]

On Sunday I am going to visit him again, I am going to look at the entire system.

My thought is to lower the low limit from 160 to 150 and see if the lower temperature stops the circulation. This will still give him warm domestic water when the boiler is not calling for heat.

The thing I do not like is it does not have a tempering valve for the domestic hot water. I can't imagine how hot the water is when the boiler calling for heat. Ouch.


I just can't understand why this has never happened to him before. Do you think the aquastat didn't turn off the pump? I guess it could go bad?

Thanks again to all the posters trying to help out.

[trout lake]

Lentz and bug
Don't get ne wrong. I did'nt say it was gravity I was simply stating a fact and mentioning the old systems "use too be gravity. Lentz your right. They havn't installed gravity systems in residential homes for 60 years. I was even too young then to even pass my dad his wrenches. Having said that:
Bug, the system sounds very strange. Take some pictures when you visit it and post them. No sut offs, no zones, no valves and no tempering valves. hmmmm?
So explain how it works! Reducing the temp on the aquastat won't help your problem. Resetting the lower limit to 150 will be too cool for you heating rads. Is the domestic run as indirect off the same system? If it is it should have its' own aquastat. You can't be running domestic watter at the 180-160 temps you indicated. You will end up scalding someone and have seripous problem.
Take some pics and explain how the system is working

[CynicX]

Sounds like it just may need your standard Bell and Gossett Flo-Control valve.

They are designed to prevent gravity circulation. Basically a weight that opens with the pressure of the circulator and closes when its off.

Trout Lake can verify I'm not the best with boiler piping so maybe I'm WAY off base here. But I cant remember (or never seen) a boiler without one. Even with zone valves they are used at "elbows" haha

http://www.statesupply.com/new/content/category/pdfs/FloContrlVlvGuide.pdf

http://www.webtrolley.com/~hpprep/images/Heat_Power/9.11_Fluid_Dynamics%20v3_page3_image5.jpg

[bug512]

Hello again.. Well after a little investigation I found it !!!


http://farm3.static.flickr.com/2777/4283642338_317302b856.jpg

It is on the pipe leaving the boiler, to the right is the supply to the baseboard radiators and to the left is the expansion tank.

I was told to do this once I found it:
I started and ran the boiler so the circulator pump came on, then I opened (bypassed) the valve for a couple on minutes. Then I turned everything off and placed the valve back to its normal position.

Thanks to everyone here with the help.