Just noticed that our boiler aquastat relay is sticking and chattering making the burner kick in and out.
I noticed the circulator running and the boiler temp was down to 120 degrees.
Turning the power off and on kicked in the burner when the power was back on.
It ran for a while and then the magnet started chattering killing and restarting the burner.
It seems intermittent because it ran ok for a while and shut down normally.

Does it need replacing, adjustment or could something else in the control circuit be causing it.
Unfortunately we're going into a cold weekend so hopefully it struggles through.

Any input would be appreciated.

 

I had the identical problem with the L8148A. I think you are correct. It is relay chatter. I replaced mine with the L7224. It's a pretty simple replacement operation.

I remember that some people on the forum talked about using an emery cloth on the relays. That may help. I'm not absolutely certain but I think someone with some really good experience talked about using a fingernail file on the relays - or many just a small file - not sure. Maybe that would help for the next short period of time. But my guess would be you will have to replace that aquastat.

Well it looks like another senior moment. I just checked my old a'stat and it's the 8124. But I think that's like the 8148.
Also, I checked and it looks like you can get a piece of emery paper between the contacts so that looks like something you could try.

 

Welcome to the forums.

How do you know it's sticking ?
If it was sticking the burner or circulator would not shut off.

If it's chattering it could be dirty contacts or a problem with the thermostat.
What are you using for a thermostat ?

 

Relay contacts in old technology controls switched 120 volts On to start burner motors. The relays often cause problems. Modern $80 burner controls use low current 24 volt T T to start burner.

A simple, low cost solution makes for 1degree temperature control can reduce fuel cost.

Use $186 aquastat with out-door reset, contacts to turn on $80 burner control TT. Added benefit are is display actual temperature (not setting), separate high & low temps, delta T and setup menus.

$186 $80 https://www.supplyhouse.com/Resideo-...ic-Oil-Primary

https://www.supplyhouse.com/Tekmar-2...iler-4150000-p

When controls on old systems fail, often lower cost modern units improve system and lower costs.

L8148A. cost $215 https://www.supplyhouse.com/Resideo-...F-differential

L7224 cost $182 https://www.supplyhouse.com/Resideo-...ronic-Aquastat

 

Pete,
I meant stuck with contacts open. Two circulators were calling (one heat and one hot water) but not running and burner not running and boiler cooled to 120. Recycling power turned the burner on and eventually circulator when up to temp.

There are two electronic Honeywell thermostats plus a hot water holding tank with it's own aquastat.

It intermittently chattered when near the hot temperature shut off; sometimes it did and sometimes it did not. Sometimes it would just click a couple times in the heating range and sometimes it chattered a lot near the top. Sometimes it does none if that.
It seems sensitive to finger tapping or handling the aquastat housing which can make the odd behavior happen or stop.

Would that not be a failing aquastat? It could be 10 to 15 years old.

 

A contact stuck in either state would not cause chatter. Is the boiler gas or oil fired?

 

Thanks everyone.
Zero degrees out this morning and cold boiler so I submitted to replacing the aquastat.
All is well again so it was a failed unit.
I understand that they are sensitive to power outages/possible surges and we've had a couple lately so maybe that is what got it.

 

You added " chattered near set temperature".
That means the aquastat thermostat was bad.

Thanks for letting us know all is well.

 

Snap48 stated If you think the old control was sensitive to power issues the solid state controls are much worse.

​​​​​​​

 

rbeck stated
"If you think the old control was sensitive to power issues the solid state controls are much worse."

You mean like my refrigerators, dishwasher, washing machine, dryer, tv............
Everything has a darned circuit board now. We fried a dishwasher before the aquastat. And a frig before that.
It's amazing that the power company has no liability.

 

.Many home electronic unit failures are due to high voltage transients coming in on 120/240 AC power. They may come from neighbors, or lighting so utility is not responsible.

Without going into long, technical explanation of transients, simple solution is installing a small $86 module on main home electric panel. The 50 KVA is for total life time, accumulated protection, not current draw, so is more than adequate for most homes.

Note: Surges are voltage swings i.e. 110 to 140 volts noticeable by homeowner.. Transients are brief spikes 1,000 volt and higher that over long term damage electronic semiconductor in home product. Many "surge protector" products are only transient. but mislabeled

The Square D-Schneider 50 KVA, $86 will probably provide lifetime protection homes. Higher KVA and prices are hard to justify. Installed on main panel two pole 20 amp breaker protects all circuits..

https://www.amazon.com/Square-Schnei...46904643&psc=1

 

Doughess,
I had been wondering about such a device. It's easy enough to install.
Thanks.

 

A whole house spike suppressor is easy to install at the main panel.
However,,,, it is not a cure all. It can reduce and eliminate some surges. Not all.

In your case... you did not have a power issue. You had a worn thermostat.

 

The cause of Snap8 failure is unknown.

Avoiding possible power failures with $86 transient protector is homeowner option but DH Post 11 did not suggest “cure all” or suggest any value as surge protector, or speculate on possible cause. Only a way that may reduce risk and prevent possible damage.

Power transients over long periods may damage any heating systems product using electricity .. Many years ago GE had high failure rate on 120 volt wall clock with with 600 volt insulation on motors,. Issue was not 110 o 140 volt surges. GE solved problem by increasing insulation to 2,000 volts.

Because many homeowners do not understand the difference, Companies use words/label surge. DH Post #11 stated “Many "surge protector" products are mislabeled transient.”

DH Post 11 did not mention any valve dealing with surges, Only transients. Apparently some DIY posters do not appreciate differences and wrongly misstate it: See Post #12 ” It can reduce and eliminate some surges. Not all.”