New To Hydronics Have Questions About New House Boiler System

[Syt0x]

Hey everybody I've got another question for the amazing people on this forum that will hopefully be easy for one of you experts to answer as it will hopefully be just an informational adventure for me. I've recently replaced the temperature pressure relief valve, expansion tank, and auto air vent for my boiler system to solve my over pressure and leak situation I had this winter which has since solved the problems. During the repair however I introduced some air into my system and it has started to create some noises. Through research I found out how to bleed the air out of a boiler system but what I currently have doesn't match those systems. Looking over what I have also raised some other questions on the purpose of various components that you fine people might be able to help me recognize and learn their function. I've attached a few pictures and questions below if anyone thinks they could help. Thank as always!

1. In picture 1 this is a picture of my zone valves that come from the output of my boiler after expansion tank and circulation pump. What is the purpose of the gate valves in this picture before the zone valves? I can't use these to bleed the system correct since they are on the output of boiler before the zones with trapped air? Are they just used to drain the individual zones for repairs?

2. In picture 2 there is a branch that connects the output side of the boiler to the input with a ball valve that is always in the closed position. On the output side it is located before the zone valves but after expansion and circulating pump. What is the purpose of this branch and valve? When would I ever want to turn it to the on position? Is it used to eliminate air if I shut off the valve going into the boiler? Confused....

3. In pictures 3 and 4 I'm showing the return side of the system into the input side of the boiler. Shouldn't there be a gate valve on this side to bleed air after forcing water to circulate the system? It seems to be missing as the only one is seen in picture 4 which heads into the boiler. Except when this is turned it drains the boiler without eliminating air. Would I need to add a gate valve to the left of the branch in pic 3 to bleed air if I shut off the ball valve to the input side of the boiler?

4. My last question is about the thermostats that are attached to the system. I have one attached to the output side of the boiler and one attached to the input side of the boiler pipe. I assume these are to prevent flue gas condensation with the return water being too cold. Is this correct? Is there a sweet spot that these should be turned to for a 1 story with basement ranch style house that is 2200 sq ft? Output is set to 200 degrees F and the input is 180 degrees F. What does the return thermostat do if it senses the water coming back is colder than the set point does it increase the speed of the circulating pump?

Holy block of text. Thank you so much for anyone that has read this far and can help!

 

[Bcarlson78248]

I have a boiler and cast iron radiators, but based on your high temperature setting I assume you have fin and copper tube convectors in each room. My cast iron runs at lower temps because the large mass retains and radiates heat longer, but tube and fin heats and cools quickly.

1. My guess is that the gate valve and ball valve combo is used to drain each of the zones individually. If you close the ball valve and open the gate valve, it looks like you could drain water from that zone.

2. Maybe just to check the pump flow in a loop?

3. For my system you have to bleed water at the radiators, and there are small bleed valves at each radiator. With the system shut down and relatively cool, I just open the bleed valve and let the air escape (its usually a very small amount) until I get water coming out. There is an automatic valve that fills tap water in near the boiler if needed. That same valve has a bypass lever that allows me to feed water in very quickly if I have drained the system and want a quick fill.

4. My controls have temperature gauges that measure in/out temps, but I think its just to monitor the boiler cycle. I'm in the DC metro area, and my minimum temp is 100 and my max is 140. I think my boiler is rated for up to 220 degrees. When the thermostat calls for heat, the circulator pump starts, and if the boiler temp is lower than 140 it fires the boiler and opens up the flue damper. Both boiler and pump run until the right room temperature is reached. However, if the water temp exceeds 140 degrees it will cycle on and off to keep it below the max temperature even if the thermostat is still calling for heat. The boiler also cycles on and off (no pump running) to keep water in the system at the minimum temperature of 100.

Bruce

 

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[Syt0x]

Thanks Bruce for your quick response. You are correct I have copper and fin radiators for my system. I haven't touched any of the settings since I bought the house as I didn't know what they controlled from the previous home owner. I've checked all of my radiators for air vents and none of them have bleeders. The system was professionally installed per previous home owner but it looks like they left out a bleeding valve on the return loop for air removal unless I'm missing something. I've got an air scoop on the outlet with an automatic air vent but it seems like the air is trapped upstairs and isn't getting pushed back towards the boiler at system pressure of 12-18 psi.

 

[Reach4]

Sytox, this comment is not about your current symptoms -- just something to take in while you are learning your system.

You should have a thermal expansion tank. I don't see it in your photos, but it is almost surely there. It should be empty of water when the system is cold. I suggest you find that, and knock on it to know how it sounds empty, so that you can check later to see if it failed. The symptoms of a failed tank is too much pressure and water coming out of the pressure relief.

 

[Syt0x]

Hey Reach thank you for the comment. You are correct I have an expansion tank that is not pictured to the left. It had gone bad and was forcing the pressure relief valve to release. The water had left deposits that were preventing the valve from closing all of the way as well so I recently replaced both the tank and the valve and it solved my issue. The problem I have now is with air trapped in the system and no way to bleed it out. Trying to see if I'm missing something in my existing system that will allow me to do that so trying to better understand what I've got.

 

[Bcarlson78248]

I have one kitchen toe-kick heater that is tube and fin, and IIRC it did not come with a bleed valve as part of the assembly. However, I added an inline ball valve shutoff at the heater and the shutoff valve had a bleeder fitting with a cap that screwed off.

I don't know why tube and fin equipment does not have bleed valves like you find on cast iron radiators. I also always assumed my toe-kick heater without a bleeder was an exception. Air rises to the top and/or gets trapped in loops, so the best place for a bleeder is at the highest point in the system. A bleeder in the basement area would not be effective because you could not force the air to go down.

Bruce

 

[Reach4]

If you have a working bleeder somewhere, you can try increasing flow through a non-bled zone. That can push air through the zone. Shutting off all of the zones except one should maximize flow in that one zone -- presuming you have one big pump. I don't know if that is what your system has.

 

[Dana]

The branch with the ball valve between in/out on the boiler is a "boiler bypass", designed to mix boiler output with water returning from radiation to keep the entering water at the boiler high enough to not cause condensation damage on the heat exchangers. This is usually only a real problem on systems with high thermal mass radiators, but long zones of fin-tube baseboard can be a problem too.

That may be what they're trying to do with the aquastats on the input and output of the boiler too, but it's hard to say for sure. What exactly do those aquastats control- the burner? The pump maybe? It looks like a hack.

But almost NO system out there needs 200F water output, and all cast iron boilers can tolerate entering water temps of 140F or higher without inducing condensation on the boiler plates. Gas burners can usually tolerate 130F entering water temps. With that much uninsulated heating plumbing at 180-200F you have a fairly significant radiator heating up the boiler room, which is a system-efficiency problem. Setting up the system to run at a more reasonable temperature and insulating the plumbing are both warranted.

Bleeding the zones at the radiator is easier than purging them with high flow. As long as there is enough flow to heat each zone most systems have an "air scoop" or other venting device at the boiler or expansion tank to eventually get rid of all the air. Isolating the boiler from the radiation with valves isn't necessary or desirable for air purging, but being able to isolate each zone with a gate valve and purge them (or work on them) one at a time is useful, ergo the gate valve and purging port at each zone valve, as well as on each return.