boiler/baseboard heat

[cgm55082]

Here's my situation: I have a Weil Mclain boiler (installed in 95) in my house that feeds baseboard radiators through three zones. It's a closed loop system and the boiler is cast iron and natural gas fired.

The system has a smaller pipe (3/4 or an inch) that goes between the main incoming and outgoing water lines. The smaller pipe that connects the mains has a lever valve on it (I'm assuming this is the bypass valve). A heating contractor told me the lever should be just partially open to allow some of the water on the hot side to warm up the cooler water of return side before it enters the boiler. The problem is the system is very loud when valve is anything but completely closed or open (causes all sorts of strange surging and clunking noises in the pipes). I had someone else look at the system and he said the valve is usually just partially opened, but since mine was making so much noise it might not hurt to completely open the valve. He didn't seem real sure of himself and now I'm completely confused. Should this connection be completely open or not? If it is left open, doesn't that just bypass the rest of the heating system or, at best, create a lot of inefficiencies? Any help would be greatly appreciated.

My second question is how detrimental it is to run glycol-based antifreeze in a closed-loop system like mine? I'd like to leave the basement zone off, or set very low, but some sections of line at the exterior wall will freeze if I do that (already happened once).

Thanks again for any help. Boiler systems are new to me, and I sure am learning a lot.

 

[oilman]

The bypass lever valve you have is a cheapskate solution to achive a low flow rate. A better component would be a flow restrictor. As this is a UK site, I don't know where you would get one in the states. But try a guy who doesn't wear a Stetson.

If you put antifreeze in, make sure it's PROPYLENE GLYCOL NOT ethylene glycol. Ethylene glycol is toxic. Over here it costs twice as much. It's also used for high performance engines. Don't put too much in or you will make it difficult to shift heat around.

 

[cgm55082]

So, given the valve that I currently have, should it be completely open or somewhere in between open and closed?

 

[DP]

The purpose of the valve is to let the pump circulate water through this valve when all motorised valves have shut down. If this valve (Bypass) was closed and all motorised valves had shut down as well, pump would be pumping water into a dead end and could burn out.

It is prudent to ensure temperature difference between flow and return (two pipes that connect to the radiators) is 11 degrees or thereabouts for cast iron.