Limit control question

mark schofield

is the radiation hot with the Tstat turned way down. possibly a bad stat or stuck zone valve. if the space is hot but the radiation is cold, could hot air be rising to the second floor.

Butch_4

Limit control question

I have a 5 year old weil-mclain furnace, oil. I have 2 zone heating. The furnace is on the first floor. The thermostats are set for 65. 1st floor stays right at 65. Upstairs it says 71 but it's set at 65. The settings on the limit control are 160 and 180. Can I safely change them so it won't go on and off so often? Would the constant on and off raise the upstairs temperature? I noticed today the limit control temp. went up to 200 after the furnace stopped for a few minutes. Right now the upstairs is set at 64 but it's 74 and hot. We have baseboard hot water heat. Thanks in advance for your time.

Timco

First...you have a boiler. To help, pictures would be nice. Do you have circulators or zone valves? Upsairs & downstairs on seperate zones? When you say limit, do you mean the aquastat or do you have a outdoor reset? What temp does the gauge say? Pressure?

Tim

Butch_4

I think there are both circulators and zone valves. I have pictures of both enclosed. Seperate thermostats on both floors. Hot water is set at 160-180. What we have noticed is that when it is calling for water and the boiler is running it is also heating my baseboard upstairs when it doesn't need it. Upstairs was set at 63 and the temperature was up to 73. We have changed thermostats so we have ruled that out. Downstairs is fine. Boiler only goes off when needed for that. Downstairs is set at 65 and it stays at 65. Hope you can help.
Thanks, Dayton

Butch_4

I think there are both circulators and zone valves. I have pictures of both enclosed. Seperate thermostats on both floors. Hot water is set at 160-180. What we have noticed is that when it is calling for water and the boiler is running it is also heating my baseboard upstairs when it doesn't need it. Upstairs was set at 63 and the temperature was up to 73. We have changed thermostats so we have ruled that out. Downstairs is fine. Boiler only goes off when needed for that. Downstairs is set at 65 and it stays at 65. Hope you can help.
Thanks, Dayton

Ted_4

Flow control

Judging from your pictures, you have individual circulators for each zone but no zone valves. First, check to see that neither circulator is running with thermostats down. When the circulators are off, flow in each zone is supposed to be stopped by a flow control valve (pictured). These flow valves have a small thumb wheel on the top. The valve for the 2nd floor zone may be stuck open, allowing gravity flow of hot water to that zone -OR- someone may have turned the thumb wheel, which lifts the valve off its seat allowing flow. Find the defective valve by checking the temperature of the supply pipe on the outlet side of the valve when thermostats are not calling for heat (and circs are not running). Check that the thumb wheel is turned fully clockwise. If it is, try tapping the valve lightly with a hammer to see if this will free it up. If none of this helps, you may need a replacement flow valve.

Unknown

coming in late...

Judging from the given pixs, sorry to be blunt, that a poorly installed bolier with pumps on the return pipings, etc... Each pump have their own relay, connected to each thermostat... Boiler, not furance, comes with one relay... Where's is the second one for the second pump? Any more plms with heating system, get a real BOILER PROFESSIAL, a true serviceperson will install the missing reilef valve discharge pipe..

Mark Wolff_2

To answer your question...

You do not want to change the high and low limits on your triple aquastat (gray box on upper right corner of boiler). The problem you will encounter if you do is a lack of hot water. The tankless coil on your boiler is marginally effective at best, just try opening a bathtub faucet to hot and filling it without running out of water. The temperature gauge on the front of the boiler reads the temperature (with a marginal degree of accuracy) at the exact location it screws into the boiler (right above the burner) and is somewhat inaccurate. The boiler does continue to rise in temperature after the burner shuts off, due to residual heat in the combustion chamber and the transfer of heat through the cast iron into the water. The triple aquastat is much more accurate, and a slight overshoot on the temp/press gauge should not be of concern.

If you increase the high limit to 190* you will have a boiler that turns on and off less frequently, but the hot upstairs will become worse. The on/off cycling is not causing the excess heat.

Due to a poor system circulation design, your system allows flow through all zones when the system circulator is running. The best way to correct this, would be to pay a professional heating company to repipe you near boiler piping, ie. switch to zone valves for each zone loop and one system circulator (one of the two existing would most likely be just fine). This will allow your zones to heat when necessary, and to isolate when not needed. Additionally, you will notice a small decrease in your electric usage due to the elimination of a circulator pump. This repiping will take several hours however your comfort will be much improved.