Hot water heating system questions

Uni R

Your system is waterlogged. There isn't enough air in your expansion tank and when the water heats up it is being forced out of the pressure relief valve.


As for your other assumptions, yes you are assuming correctly. The thermostat will tell the boiler whether or not it should be producing heat. When that is happening the boiler will heat up to the high point and then cut out until the low point and continue cycling in this manner until the thermostat is satisfied.

Sounds like you have a monoflo system. If your heat is even around the house, don't mess with the piping. If certain radiators don't have heat then they too need to be bled.

Derick Bartelings

Hot water heating system questions

I live in Canada, close to Niagara Falls, and am trying to understand the hot water heating system in a house that I just purchased.

It is from the 1950's, but the oil hot water system was upgraded in 1991 with a gas conversion package being installed on the boiler (an old cast iron system).

The piping is (all copper) 1 1/2 inch loop, with the radiators in parallel to the loop, which does not make sense to me, since I am used to radiators being in parallel to each other with a supply and return line at either end. (even the radiators being in series sounds better than a loop with radiators feeding off the loop)

Also, the filling station is straight off the cold water line, with a turn valve, check valve, pressure relief valve, ball valve and pressure gage in series, connected to the return line, open constantly and draining (dripping) constantly. The pressure goes from about 15 at rest to 32 psi during running conditions, at which time the system drains in a trickle. Should this be left on or off?

Lastly, the boiler controls are temp. sensors on the return line ( on top of the boiler) for the max. water temp set to about 150-160F, and the pump on/off switch set at about 120F. and the wall thermostat controlling the boiler flame unit.what are the optimal settings for the water temp for the boiler and pump switches?

Am I correct in assuming the demand should switch on the flame, and the rising water temp should kick in the pump at the min. temp. till there is no demand, the flame stops and the pump kicks off when the water temp goes low? (and the heater stays off till the water temp drops below 150F)
Ofcourse with the water going in a loop, the water temp will go high fast, but not enough heat will go to the radiators.

Could you let me know if my thoughts are correct, and I should be putting another return line next to the supply line, and rerun all the radiator returns to the return line, or could I just put a restriction in the feed line between all supply and return points for each radiator and thereby force more water through the radiators. (this I assume would not be the best way, but surely the easiest way.

Earthfire

understanding

This book from the books and more link at the top left will be invaluable in helping you understand your heating system and to decide if there are any changes that you might want to have made to it to make it more efficient. "Pumping Away and other really cool piping options for hydronic systems". Do order it. And I agree that your expansion tank is probably waterlogged and needs to be serviced. I would recommend that until you fully understand how your system is operating that you have a reliable pro do a complete system clean and tune which includes a combustion analysis and CO test

Steve Paul

Juxtaposition of various paraphanalia

Derick,
If the water supply and position of the relief valve are as you describe, then you have a problem. If in fact the pressure relief valve can be valved off from the boiler, then it is theoretically possible to close the valve and run the boiler without relief valve protection. The relief valve must be able to feel the pressure of the boiler with no valves of any kind in between. This is a very serious and dangerous condition. PlEASE GET SOMEONE WHO IS QUALIFIED TO CHECK THE SYSTEM OUT!

Derick Bartelings

juxtaposition of valves

The way I described the valve arrangement is the way it is at present, and I am not happy about the layout, and I do agree that it is not the way it should be done, which is why I have not touched "that valve" at all, and would like to take it out. But, at the same time I would like to simplify it, and maybe leave the filler turned off, and only check it every now and again, instead of leaving it running all the time. For now, I will empty the overhead pressure tank (galvanized iron) and see if it helps, it can be closed off from the system, and drained separately.
Thanks for the help.

Derick Bartelings

expansion tank

You may be right, the expansion tank is overhead, galvanized, and can be bled easily, so I will give that a try. I am really considering getting a new system installed to get rid of the old pump, boiler and expansion tank, and get a new bladder tank, and a smaller, more efficient boiler, but till then I still want the system to work ok. (I will not do the changes till it gets warmer)
But I am wondering if I can close off the filling system and only turn it on once a week or a month, instead of leaving it open constantly. What I am trying to find is information what the most logical, best and energy efficient way is to go with the present system till I can get it replaced.

Derick Bartelings

get more info

I will get more info before I do anything else, and I will have a look at the book first before I do any modifications.

Uni R

juxtaposition of valves

If you are draining the tank, be sure to drain it completely and not leave an air vacuum in it. You may wish to use a short hose that just reaches your drain. Also, after you have emptied the tank, shut the feed off to your system before opening the valve to the tank. Then slowly allow the feed in, otherwise you'll get a lot of air that will probably end up in the rads.

Uni R

Feed valve

Unless you have a properly functioning low water cut off, you should leave the feed valve on. A water leak could ruin stuff in your basement but your boiler exploding could ruin you.

Derick Bartelings

juxtaposition of valves

thank you for that info, I will be doing it tonight.
I will shut the supply line off, and make sure the system is not circulating when I drain and reconnect the tank.

Derick Bartelings

low water cutoff

I don't believe there is anything like a low water cutoff in the boiler system, another good reason to switch to a newer one next summer.

Joe_30

Temporarily shut off valve between expansion tank and boiler before draining tank. Reopen when done draining, and tank drain is closed again.. Was this mentioned. Otherwise you drain the upper parts of the system through the tank.
Run a temporary hose to basement drain for convenience.

Derick Bartelings

Draining the expansion tank

Thanks for all the advice on how to drain the expansion tank, but I looked at it and noticed that the valve to it was closed, so after closing the water supply, opening up the tank, and slowly allowing the filling to take place, and the system pressure to get up from 0 to 12 PSI again. It now only drips from the drain from time to time... a minimal amount.
I also vented all the radiators, and have the boiler working temp set at 160F and the pump startup temp set at 116F. It is working a lot better, or at least till I get something done next summer.

Derick Bartelings

Hot water system problems resolved

Thanks for all the advice, the constant draining has been resolved with opening up the expansion tank (it had been closed). I will be checking with different contractors about what the optimal solution will be for the piping layout when I get the new system installednext summer. I also want to ask about local radiator thermostats, and what piping system would be optimal.
But for now the system is working a lot better, keeping the temperature within one degree from setpoint in the house.

Derick Bartelings

monoflow system?

I read up on monoflow (?sp.)systems, but for that the T's would have to be special? In this case there are no special tees, everything is thinwall 1 1/2" copper in the whole loop, with tees off in 1/2" and 3/4", depending on the length of the run.