Replace circulator pump without draining boiler?

Ahomeowner

Can I close the isolator valve above the pump as well as the valve below the fill valve and leave all of the water in the boiler and the baseboards (fin-tube?). I don’t think so because the bottom valve is in the wrong location, but just checking. Taco installation instructions state to reduce system pressure to 0 PSI and allow system to return to room temperature. I was worried about letting the boiler get that cool and also about draining it while it’s hot. Also, the boiler is currently on but there is no heat upstairs so the water in the baseboards is 40F (maybe colder by tomorrow.). Could I do damage by turning up the thermostats and introducing that cold water into the boiler? What’s the best way to prevent damage? I may have caused damage to this pump by filling the system in the off season a couple of times and then not running the circulator pump immediately as per the installation instructions. We also have sediment in our well water which could have caused damage. I’m guessing that the only way to run the pump would be to turn up the thermostat(s)? Thanks for your help.

Zman

Is there a valve on the supply side?
If there is, you should be able to trap the water upstairs then just do a partial drain of the boiler.
As long as the boiler is not so hot it will burn you, you can drain it down whenever.
When you go to start it up, fill the system with cold water, then fire the boiler.
It looks like yours is probably set up to purge by closing the valve above the circulator then bleeding the hose bib above that valve.
Pictures taken from farther back would help answer any other questions.

HVACNUT

Yeah if you close both those valves, valve on the supply if any, and close all air vents. 
You dont need to drain the boiler, but drop the pressure to zero.
6 ft washing machine hose into a 5 gallon bucket. Drain from the bottom of the boiler only until the water stops and pressure reads zero. 
Leave the hose out of the water so you can see when it stops and close the valve as soon as it does.
Then it should be good.
To fill, open the feed valve and then immediately open the air vents. Then other valves and check the heat.
Do as much prep as you can before removing and installing. 

Ahomeowner

Thanks. Here is a picture of the entire system. We have an Amtrol Air Purger so I guess I would tighten the nut on top of that? Also, as far as a valve on the supply side, there is a valve directly above the backflow preventer which I have marked with blue masking tape as “cold water in.” There are also two more valves (hot and cold) in the pipes directly above the oil filter. I believe the hot valve is DHW and the cold valve may be another valve in the supply line. I’m not sure why there would be 2 valves in the supply line, but that’s what it looks like to me. It also looks like there are 2 valves on the DHW side. I marked one with blue tape as “hot water out” so I could turn off the hot water to do plumbing work upstairs, but as I look closer at this, it looks like some kind of tempering set-up. If somebody could explain the purpose of all of the valves it would really help me in the future.  The reason the system was drained a couple of times in the off season is because I didn’t know how to turn off the water to make plumbing repairs upstairs so I just drained the system and then refilled it afterwards without running the circulator pump. To do this pump replacement, I am inclined to just close every single ball valve on the system. I was told that there is a procedure for starting a boiler when it’s cold in order to prevent damage. I am worried about causing damage because I don’t know what I don’t know. As I said, the water in the baseboards is 40F right now because that’s the interior temp of the house, which is colder than our well water. Thanks  Thanks 

jad3675

Are you sure it is the circulator that is bad and not your zone controls or the aquastat? I've had a Honeywell aquastat where the circulator circuit died; boiler continued to fire and the water is the system got nice and hot and circulated via convection.

I also suppose the system could need bleeding, but you'd still get some circulation just with noise.

EBEBRATT-Ed

@Ahomeowner

I would install a new air vent on top of your air scoop while you have it shut down

Ahomeowner

jad3675 said:

Are you sure it is the circulator that is bad and not your zone controls or the aquastat? I've had a Honeywell aquastat where the circulator circuit died; boiler continued to fire and the water is the system got nice and hot and circulated via convection. I also suppose the system could need bleeding, but you'd still get some circulation just with noise.

That’s a good question considering I’m a layperson. I tried to troubleshoot as best I could. We have 2 zones so I turned up the thermostat for zone 1 and the boiler fired up but turned off once it reached the high limit. I read the manual for the Aquastat and learned how to scroll through the codes. There are no error codes. When the thermostat was off, the code read “tt” “OFF” and when the thermostat was on, the code read “tt” “ON” which indicates to me that the aquastat is getting a signal from the thermostat. I turned up the thermostat again and then manually opened both zone valves. The switch for zone 1, which was calling for heat, was easy to slide while the other one was more difficult. This lead me to believe that the zone valve for zone 1 was already open, as it should be when it’s calling for heat. So now I’m thinking it’s not the thermostats and it’s not the zone valves and obviously it has nothing to do with the fuel or the burner. So it can only be the pump or the signal from the aquastat to the pump. I put my hand on the circulator pump before the boiler fired and it was not hot. After the thermostat called for heat, the pump began to get warmer. This lead me to believe that it was getting a signal from the aquastat and was powered up, but is broken. I don’t think that the problem is air because we have an air purger and there is a purge valve on top. I touched the top of the valve and water came out, so I don’t think there’s an excessive amount of air in there. Plus, the pump and pipes are making no sounds whatsoever. Also, I tapped the expansion tank and it sounds empty. Attached is the troubleshooting section from the aquastat manual. It mentions checking the wiring, but I don’t know how to do that. Maybe with a continuity tester? I still think that with the pump getting warm, that is the most likely cause.

jad3675

Two zones and two thermostats, right? And one zone has heat, just not the other? What does your zone panel look like?

John

Zman

If you download the Danfoss magnetic tool app and put your phone on the end of the circulator it will tell you if it is spinning. A multimeter would tell you if it has power.

Ahomeowner

jad3675 said:

Two zones and two thermostats, right? And one zone has heat, just not the other? What does your zone panel look like? John

We have no heat in the house, only domestic hot water from the boiler. And two thermostats, two zone valves and one circulator pump.

Ahomeowner

Zman said:

If you download the Danfoss magnetic tool app and put your phone on the end of the circulator it will tell you if it is spinning. A multimeter would tell you if it has power.

Thank you Zman. I will look into the app. Sounds like a great tool!  I use a multimeter to test tor continuity. I guess I forgot the correct name! But I’m not really sure where to put the contacts since I don’t see labels in the aquastat.

Zman

It looks like the circulator is wired to the Blue and White wires coming into the top left of the aquastat. Set your multimeter to AC volts and put the probes on those 2 wires and you should read +/- 120 volts.

JakeCK

Is the supply side valve behind the expansion tank right after the air purger? Close that, the valve right before the circulator on the return, and the valve for the auto fill. And drain like was suggested using the boiler drain below the circulator. As its draining remove the air bleeder to make it drain quicker since it needs replaced anyways. You might be able to use this to purge most of the air quicker if you can close the fill valve before it sprays out.

This is assuming the problem is the circulator.

Please for the love of god make sure you have power turned off and it is cool before you do this. If its bouncing off the aquastat because of a bad circulator or zone valve that water can burn you in seconds. The aquastat is normally set to around 160-180.

Also there is a good amount of corrosion on the vent. Have you ever inspected your flue and heat exchanger?