McDonnell #61 low water cut off automatic reset / convert to manual

randallkc

I have a system with two McDonnell low water cut offs The first is for the auto feeder and the second is to shut down the system. I need to convert the second to a manual reset.

Is there a way to do that with a electronic box? The 61 is no longer in production.

randallkc

I think I just answered my own question. I am going to install a latching relay circuit to the output of the 61. This will creat the hold function.

It just seems crazy to spend $600 on a new system when I can buy the relay for $10 and spend 15 minutes hooking it up.

JStar

http://www.boilersupplies.com/mcdonnell-miller-controls/mcdonnell-miller-no-11-switch

Part #309151
Catalog #11-M

I would be hesistant about altering the functionality of a safety device. Use the factory approved and UL listed parts.

nicholas bonham-carter

Why exactly is the manual reset needed, if the boiler was installed without it?
You could just verify that the auto feeder LWCO shuts off the system, and valve off the water supply, so it keeps the boiler off until you arrive and refill it.--NBC

JStar

It's required on commercial boilers. If you turn the water feed off, what if the boiler keeps running without water?

JUGHNE

If your added relay latch was holding the boiler off, (no heat), someone may cycle the power switch, common practice. Then you would lose the "latch out" function which would defeat the purpose of having a manual reset. That would be a specific reset requiring attention of someone who should know there is a problem.

nicholas bonham-carter

If the boiler runs low on water, then one or both LWCO's will cut the burner off.--NBC

JStar

*should

JUGHNE

I'm really out in the outback of the boondocks in NE. The only AHJ for controls is actually the state which hands the job over to the insurance company who insures and inspects the boilers annually. The Hartford insurance company said this must have a second manual/reset LWCO. So be it, make it so.

If things really go south with a boiler and your insurance doesn't have a record of safety devices that they deem necessary then they may have a way out of paying. (I've heard they are well skilled in this at every application).
J-star gave you a lead on the correct switch, if you are skilled enough to install the latching relay, ( which is actually very creative by the way IMO), changing the switch only should be simple.....but if these both have floats in them I sure would open them for inspection, there could be surprises inside that warrant changing the complete LWCO's. IMHO

SWEI

{slightly OT} I always try to be there when the Hartford guy shows up for the annual inspection. The row of mod/cons hanging on the wall means he won't be coming back again.

randallkc

True if power was recycled it would reset the latch.... But. The low water cut off situation would still exist and the latch would again be re-armed requiring a manual reset Thus alerting the operator

The State boiler inspector approved the solution.

I did find some manual magnetic relays. They would require a true manual reset.

Seems crazy to spend $600 when you don't have to.

JUGHNE

I would sure go for the manual latching relay because.......
the scenario as follows is not impossible: condensate water is slow to return for any number of reasons......the first fill LWCO doesn't fill or shut down because of stuck float.....the second kill LWCO does its job....fire off.......condensate returns both LWCO are happy and restart boiler. If you have your simple latch relay and someones cycles the power you restart and never know the problem. Or it may not have been a low water problem, the ignition could have been locked out because of some flame failure issue...cycling power sometimes resets this condition also. This could happen everyday.
Been there, done that......"can't find anything wrong.....call back if it happens again"

With some form of manual reset button then you or serviceperson would know there was a low water condition and proceed accordingly. Is your first LWCO a float type device with blow down testing that could be done weekly?

randallkc

both are

JUGHNE

So you could test both weekly by blowing down, the first would kill and fill.......the second would kill and require your manual reset. That is what the Hartford people want demonstrated when they arrive around here. That is what I do weekly for the steamers I monitor. On internal boiler inspections some want the LWCO opened to see the condition of the float and its chamber. Then during heating season they want to observe the functions described above.

randallkc

JUGHNE said:

So you could test both weekly by blowing down, the first would kill and fill.......the second would kill and require your manual reset. That is what the Hartford people want demonstrated when they arrive around here. That is what I do weekly for the steamers I monitor. On internal boiler inspections some want the LWCO opened to see the condition of the float and its chamber. Then during heating season they want to observe the functions described above.

randallkc

That is how this system is setup except for the manual reset part which I will be adding next week with a electronic trickery.

No way I'm paying $600 for a new low water cutoff.
Will be using the magnetic manual reset latching relay. I'm even going to hook up the bell so the shop keeper upstairs knows.

This is a 1880's frontier town downtown building and way cool