LWCO is triggered daily

frank100

Hi, I have a brand new gas hot water heating system. After repairing one leaking from a heating water pipe, the system triggered LWCO daily.  Any suggestion to prevent it from happening? The pressure shows below is when the heating is not on. It seems there is enough water in the system as I have another identical system with the same pressure, and the other system does not trigger the LWCO at all. BTW, May I ask what is the red pointer for in the meter? Thanks.

Gilmorrie

The system pressure doesn't tell anything about whether there is enough water. You may have a potentially dangerous situation. Call a plumber ASAP.

frank100

Thanks. I have two external LWCOs, one is automatic reset and one is manual reset. When it triggered, more water get feeded and I manually reset the LWCO, and the boiler can start working. My question is how I know whether I should manually feed more water in . As when I feed more water, the pressure is getting higher. The only difference between my two systems are the red pointers positions. The first is the system does not triggered the LWCO and the 2nd is the system triggered LWCO. 

EdTheHeaterMan

The red pointers are for reference. You place them at whatever position you want. Some mechanics will set the pointer to 200°F and tell the customer that if the white pointer (temperature gauge) goes above the red pointer (where ever you set it) then there is a problem and they should call for service. Personally I don't bother with it ever. It is meaningless unless YOU give it a meaning.

EdTheHeaterMan

As far as your Manual reset LWCO... You mentioned you have another identical system. and you mentioned the you have an automatic reset LWCO and a manual reset LWCO. So to be clear... Does that mean that you have 4 LWCO controls? Or do you have two LWCO controls and one system has the auto reset and the other system has the manual reset?

If you have only 2 LWCO then why do you need a manual reset, the auto reset will take care of itself automatically.

Is this a commercial property?

Jamie Hall

The white pointer on the system which I think is giving you trouble strikes me as a bit high -- it looks as though it's reading about 20 psi. I would wonder what it reads when the system is hot?

Have you ever noticed any discharge from the pressure relief valve, even dribbling?

You should never have to add water to a hot water heating system -- or at best very rarely. The system, after all, is closed. So the water you are adding at the boiler has to be leaving the system somewhere, and it shouldn't be.

The obvious possibility is a leak somewhere. Another, however, is that the expansion tank is not doing its job -- either failed or not properly pressurized -- and the expanding water is raising the pressure enough to open the pressure relief valve a bit.

EdTheHeaterMan

And finally, Get a damp rag and wipe down that boiler, it looks disgusting. You should be ashamed of yourself, Did your mother leave your kitchen table like that? I think not!

frank100

Thanks. My other questions are how do I know whether there is enough water in this system as the other system does not trigger the LWCO at all with the same pressure. LIs there a way for me to find out whether there is enough water? My understanding is that if there is no water, the pressure will be zero, and it is 100 now, and it seems that it has enough water. But I am not sure why it triggers the LWCO, and the heater is working at night and next morning the LWCO red light is on and I reset it and the heater works. Should I feed manually more water in?  Could it because some air is still in the system as they fixed the leaking hot water pipe? 

frank100

Thanks Ed and Jamie.

I have two identical systems. Each system has two LWCOs. The system comes with an automatic LWCO and a manual LWCO has to be added to pass the inspection. 

I will watch it dripping or not, and also check whether there is any leaking. Also wipe it. 

neilc

frank100 said:

Thanks. My other questions are how do I know whether there is enough water in this system as the other system does not trigger the LWCO at all with the same pressure. LIs there a way for me to find out whether there is enough water? My understanding is that if there is no water, the pressure will be zero, and it is 100 now, and it seems that it has enough water. But I am not sure why it triggers the LWCO, and the heater is working at night and next morning the LWCO red light is on and I reset it and the heater works. Should I feed manually more water in?  Could it because some air is still in the system as they fixed the leaking hot water pipe? 

about having enough water,
or no water and a lot of air,

what do you have upstairs for rads or baseboard?
are there any air vents up there somewhere on the emitters?

if so, you could shut off the boiler and circulator(s) for this test,
go to your highest air vent and open it up,
do you get air, or water,
if air, let it all out,
if water, it should have a little pressure behind it, and if the vent runs for a bit, the pressure should hold steady,
if water holds pressure at your highest rad and its airvent,
then you know you have enough water, AT THAT MOMENT,

better best question, where's the guys that did this work and left you like this?

EdTheHeaterMan

@frank100, only kidding about wiping down the boiler...

Does one of the boilers operate the lower floors and the other boiler operate the upper floors?

I have had LWCO problems with a poor location choice. Just a stab in the dark... how easy would it be to swap the location of the manual with the automatic control. the probes are probably the same, so it is just changing the location if the wires are long enough. The idea is to have an operating control and a manual reset backup. If there is a place that for some reason air pockets form but correct themselves ins short order, then the auto reset LWCO should be located at that point in the system. The manual reset one should be at the other location.

...Just a thought.

After thought:
Perhaps a completely different location for the probe is in order. As long as there is 15 PSI (or 100 kPa for you foreigners) and some type of functioning air vent above the boiler, then there is little chance of dry firing that boiler. And if that condition did exist you have 2 LWCOs to protect the boiler.

Whatever you do, don't "fix" it with a jumper wire that disables the LWCO. You have a condition that should be monitored and bypassing the safety control is no way to correct it.