Update: F*&%ing heat...

[Edwin Pawlowski]

The circulator pump is started by the house thermostat. When the T'stat calls for heat, it switches on the circulator so the hot water gets to the radiators. You have a reservoir of hot water sitting in the heater.

As the water circulates, the cooler water that has been sitting in the pipes is pushed into the heater as the hot water is pushed out. When the temperature of the water in the heater drops, the burner comes on. There should be two dials, one set to the upper limit, the 190 that you see, the other is probably around 160 or so. Burner comes on at the low setting, goes off at the high setting. Circulator continues to move water until the thermostat for the house is satisfied.

The hotter the water, the more heat energy it will carry to the radiators to be given off to the air in the rooms. You would do well to find a basic short explanation of thermal transfer and a simple description of how the heating system works. That will make troubleshooting easier.

The circulator is on the return side because it is easier to pump the cold water compared to the hotter water. The radiators don't know and don't care where the pump is. Cold water is more dense than hot. Less likely to have cavitation also as the water is sitting on top of the inlet side.

[Gary R. Lloyd]

You may very well be right, but I have seen them wired every which way, so I wouldn't make any such assumptions.

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Gary R. Lloyd CMS HVACR Troubleshooting Books/Software Written by a veteran Service Technician

[hotblues20]

honeywell

better

We might be getting somewhere guys. The Taco is connected to the honewell controller, but it does not have any other control - I popped the cover on the Taco and there is only wiring and a small cylinder that does I don't know what...but it does not appear the circ starts moving until the hot water loops back to it.

The bioler gets hot for 15 minutes - then cycles off @ 190, then the circ pump comes on by itself, dunping the return water into the boiler, making the temp drop almost immedately to 160, thus making the boiler fire again. At that point the circulation is continuous hot water and good heat.

When the thermo is set at say 72 and the temp drops to 71, the bruner will fire, but only enough to get the outgoing pipes hot - once it get to 72, that's it...the hot water never has a chance to return to the circ pump and make it do its thing.

That is my impression - short cycling issue. But can I make the circ pump move the water sooner? I will try the temp dial in the Honeywell, it seems to be set at 190, but my temp gauge regularly goes over 190 and the burner still cranks...

Anyway - Merry Xmas to everyone - and thanks for the continued input. Bluesman

[Edwin Pawlowski]

OK, so the T'stat goes through the controler to the circulator. If the circulator does not start until the hot water gets to it, something is wrong as that is an illogical method. The job of the circulator is to move the hot water so it does get to it, as well as the entire heating system.

Could there be an aquastat that is not working or set properly? It may be possible that there is an aquastat that will not allow the circulator to run if the water in not at a certain temperature. I'd guess it to be closer to

140 or 160 than the upper limit of 190.

In commercial/industrial systems it is common for individual unit heaters to have an aquastat that will not allow the fan to come on unless there is hot water or steam coming to it from the central boiler. That allows individual controls at many points in a large complex.

This goes back to the aquastat. There is no reason that the circulator would not come on when heat is called for. Perhaps the previous owner re-wired something or the installer is an idiot. As I sit and type this, my heat just kicked on and I can hear the hot water circulating. The burner has not run yet and probably won't for another couple of minutes until the colder water gets back to the heater.

Not seeing your setup I don't know what to adjust, but something is not right. If you want to make changes, be sure to write down the original settings and make one change at a time to see what happens.

It's getting cold so I home somethihng help and you get it adjusted properly. Worst case scenario is you call a heater tech that knows your unit and gets it set properly. It would be a shame to spend $100 to have him turn a dial to the correct setting, OHOH, he can point out how the ystem works and you gain some knowledge for the future.

[HaHaHa]

There should be 3 completely independant cause & effect thermostatic operations occuring.

The first is the low-limit dial in the honeywell controller which acts as a switch to cut OFF the taco circulator when the boiler is operating at a temperature lower than the limit set on the low limit dial. - This is to prevent the boiler from heating the home when the domestic hot water coil is under load. It's usually 160 but sometimes as low as 140.

The second is the high limit dial which is what actually fires the boiler, or not, to keep the interior temperature of the boiler within the prescribed temperature range. It's usually set at 190.

The third is the wall thermostat, set wherever you find it comfortable. When it calls for heat, it makes a contact close which turns on the taco circulator which pumps the 190 degree boiler water around your baseboard loop. It will continue to do this as long as the boiler water remains above the setting on the low limit dial.

This almost instantly triggers the high limit dial to fire the boiler, because of the inrush of colder baseboard water. But if that inrush is continuious, it may trigger the circulator to switch off via the low limit if the boiler gets colder than the setting on the low limit. Once the boiler warms up though (which will occur fairly quickly, as the circulator pump is now off) it will resume pumping baseboard water.

This is the most common way a boiler is wired if the boiler also provides domestic hot water via a built-in coil, and there are live-volt thermostats and typically only 1 or 2 zones, each zone with it's own circulator pump. [e-mail]

[hotblues20]

HaH ~

Thanks for the detailed explanation. The Honeywell Aqaustat controller has a single dial - the setting indicated at midlevel on the left (if that is the read point) is 190 degrees.

According to your desription - this is both the high limit and low limit dial? Not sure how they are one and the same - but earlier today while the burner was firing I turned the dial, and the burner, not the circ pump, turned on and off...How can I adjust it to get the circ pump to do its thing at a lower temp to keep the hot water flowing through the system?

Thoughts are appreciated...It is going to be single digits tomorrow... Bluesman

[Dan]

You need to rewire the low-voltage circuit so that the gas valve circuit is not powered unless the thermostat calls for heat. Not difficult, but hard to explain without seeing your system first hand. This would keep the pump working as long as heat is called for and allow the aquastat to be set to a lower temperature at times when that would be sufficient. Keeping a boiler full of hot water when not needed adds significantly to off-cycle heat losses.

Dan

[Gary R. Lloyd]

Most likely there is a pump relay which is energized by the thermostat to start the pump. Follow the pump wiring to find it. Make sure all of the wiring connections are tight. You may need to replace that relay.

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Gary R. Lloyd CMS HVACR Troubleshooting Books/Software Written by a veteran Service Technician

[hotblues20]

Hi Gary, I did check the circ pump connections, and they are nice and tiight, both at the pump and the AQ controller. (I also got nicely electrocuted when messing with the controller when the burner was firing)

But here we go again. Last might it was single digits, Bedroom radiator was cranking nicely, but the rest of the house was 60 degrees when I woke up, with 3 radiators cold.

The boiler is humming at 200 degrees (it only cycles off when it hits the high limit on the aquastat) but the hot water is just not getting to 3 of 8 radiators. I called the oil Co, they are sending out a tech. I am going to bombard him with questions. I still think it may be the circ pump. There is hot water, good pressure, no air in the lines, and SOME of the radiators are getting very hot.

At least we may be getting somewhere, and boy I sure am getting an education on my heating system...I mean, I had no idea what an aquastat controller or circulation pump was three weeks ago. Thanks - I will keep youy updated...

Bluesman

[Gary R. Lloyd]

Was the pump running?

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Gary R. Lloyd CMS HVACR Troubleshooting Books/Software Written by a veteran Service Technician

[hotblues20]

I don't think so - the burner is so loud it is hard to tell, but the pump is not getting real hot, and it is certainly not running on its own when the boiler is off.

I am guessing relay, bad wire, or the pump itself. Hopefully I will know soon enough. The tech is supposed to be here by now...

Bluesman

[hotblues20]

************** IT IS FIXED !!!!!!!!!!!!!!!!!!!!!!!!!!!! ****************

It was the Honeywell Aquastat relay. The elctrical connection to the pump was dead, so the circ pump never moved the hot water to the hard to reach radiators. I knew it was the F%$ing circ pump!

The part was covered under my service plan, so I paid nothing, and I got a hell of an education learning about it. While I asking the tech all the questions he eventually asked if I wanted a job...

Thanks again guys...I am sure I will have some more stupid questions going forward, but hopefully not about this again. Regards,

Bluesman

[hotblues20]

************** IT IS FIXED !!!!!!!!!!!!!!!!!!!!!!!!!!!! ****************

It was the Honeywell Aquastat relay. The elctrical connection to the pump was dead, so the circ pump never moved the hot water to the hard to reach radiators. I knew it was the F%$ing circ pump!

The part was covered under my service plan, so I paid nothing, and I got a hell of an education learning about it. While I asking the tech all the questions he eventually asked if I wanted a job...

Thanks again guys...I am sure I will have some more stupid questions going forward, but hopefully not about this again. Regards,

Bluesman

[Edwin Pawlowski]

Glad it is going again. The problem we have diagnosing over a computer is not being able to check voltages and stuff that takes only a few minutes when you are there and see just how it is wired. At least your toes will be warm in the morning.

[Gary R. Lloyd]

Glad to hear you got it fixed. :)

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Gary R. Lloyd CMS HVACR Troubleshooting Books/Software Written by a veteran Service Technician

[Matt Howell]