ByPassing Low Limit Switch on Honeywell l8124a aquastat

Mike Z.

Hello I just purchased a new Crown Boiler TWZ125 and a indirect fired hotwater tank Crown Model #Megastor MS-40. The boiler i originaly wanted to purchase was the one without the tankless hot water coil. Well the supply store only had the one in stock with the coil, so he gave me the boiler with the coil installed. I do not want to use the coil. So basically my question is how do i bypass the low limit switch on the Honeywell L8124A Aquastat.

Thanks in advance,
-Mike

Bill Nye_2

Why

Why? would you want to defeat it? Couldn't you just turn it down to 120° or so? The indirect would prefer it, on a call for hot water the indirect won't have to heat the boiler until it warms up. The boiler will last longer and be easier to service. Warm start, ask your burner man.JMO

Or you could put an 8148 on it. If you start pulling wires out of the 8124 to alter its function you just became the manufacturer and if any unforseen incident occurs [run away boiler etc.] you were the last to touch it and assume all liability. Unless of course you get something in writing from Honeywell

Steve_35

Replace the aquastat

As Bill siad you don't wnat the liability.

Mike Z.

Re: why

Why pay for the fuel to heat water in the boiler while i have a storage tank holding hot water? Is it economical to maintain the low limit in the boiler and constantly reheating the water in the boiler when im not calling for hot water???

Bill Nye_2

It would

It would cost very little to maintain your well insulated boiler at a temperature 50 - 80 degrees above room temperature. The benefit would be you would not have to cold start your boiler from room temperature. Like racing a car with a running start versus the car starting from a dead stand still.

The burner flame will be less efficient until the boiler warms up and you can condense the flue gas which can cause sooting. If you maintain the boiler near or at the dew point of the flue gas you'll have no sooting or condensing.

In most cases the water in the indirect will be warmer than the water in the boiler. On a call for hot water first AM when the whole family heads for the shower the boiler will actually cool the indirect until it warms up.[no running start] It will have to catch up. Go ahead and add a Taco zone valve and you made matters worse by 90 seconds. Wait for the zone valve to open, wait for the burner to start 20 to 30 more seconds if you have pre purge , now wait for the burner to catch up. Now your customer used up all of the stored hot water. Rich people hate cold showers. Explain to them why $ 50 worth of fuel per year will make their equipment last longer and guarantee a good chance of a hot shower.

ps , you already paid to heat the stored water in the indirect that will be cooled off by the cold boiler water

Mike Z.

Thanks

Thanks Alot, That was the knowledge i was searching for, It makes alot of sense now.

Thanks Again,
Mike

Bill Nye_2

Mike,

a lot of people would disagree with me. Cold start became popular because the control is cheaper than the one you already have.

I throw away the 8148 and purchase the 8124. My supplier won't even give credit on the brand new 8148's because we bring so many back on new installs. You have the better control why not use it?

Another benefit is , it will manage your heating circulator. The 8124 has a reverse acting aquastat that holds the pump out until minimum water temperature is reached This could prevent condensing and thermal shock to the boiler from cold return water and give the boiler half a chance to get ahead of the demand a little.


I have seen cases where I had to disconnect all t-stat wires so the boiler could get above 120°! It was a no heat call in extreme weather in a big old house. The burner ran for half an hour before I could bring all zones back on. You had to have been there I guess.

Robert O'Connor_6

Answer

pull the wire on the top right of the white block. Test and see it will not allow the circ to run until it meets low limit set point. Nor will it maintain temp.

I agree with Bill but this is the answer to your question.

Regards

Robert

ME

Steve_35

There are friendly disagreements on this.

Why don't I live my car running all the time so it's ready to go when I am? These cold days that's a great question.

I'm of the cold start mind set. I know the WH will only make a call every other day if no one is using DHW. Now that's not real world unless the folks are gone for a day or two, but then that does happen.

I do agree that the possiblity of running out of DHW is greater with a cold start but realisticly I've only run into that with two clients. Both times in the summer and in both cases it was the wife's shower. The husband started the his shower while the wife started a load of dishes and the washing machine. Then she hopped in the shower right after him. Give the system about 10 minutes and they don't run out any longer.

I'm curious as to the $50/yr to maintain the boiler and the claim the equipment will last longer running more often.

Firedragon_4

I agree with most of the

comments here regarding warm-start (120F+). I don't like cold-start anymore although I was one of it's originators. Installers like it, service people don't, that says a lot!!!

Another idea!

Have the tankless in the boiler connected to the inlet of the indirect. It will act as a pre-heater and make your indirect that much more efficient. Even if it loses efficiency due to scaling in a while, it still validates the 120F stand-by temperature.

Don't disconnect the wires in the control, in a liability matter it could make you responsible, FACT! I've seen lawsuits lost over less than that!

Steve_35

> comments here regarding warm-start (120F+). I

> don't like cold-start anymore although I was one

> of it's originators. Installers like it, service

> people don't, that says a lot!!!


We do both installs and service. Why would installers like cold start and service guys like maintaining boilers?

> Have the tankless in the boiler

> connected to the inlet of the indirect. It will

> act as a pre-heater and make your indirect that

> much more efficient. Even if it loses efficiency

> due to scaling in a while, it still validates the

> 120F stand-by temperature.


The only problem I see with this is you're restricting the flow of DHW by what will move through the tankless coil. In most cases this is an ever decreasing amount.

Firedragon_4

If you clean boilers

on a regular basis (sorry, I don't know you) you can SEE the difference. The effect on a gas boiler is bad, ask Timmie, oil is gadzooks and yuck!

JMO, but if the city water is not full of potasium, lime, whatever, the two coils will muck up at about the same time. As we know the tankless is easier to clean, IMO, with acids or shocking. Most indirects require pulling the coil and that ain't no fun.

One other thing on the service vs. install thing. Installers have an easier time WIRING cold-start over many DHW installs, that's according to a lot of guys I have taught. To me, I never saw a difference, might be the controls???

Steve_35

Cold vs Warm Start

> on a regular basis (sorry, I don't know you) you

> can SEE the difference. The effect on a gas

> boiler is bad, ask Timmie, oil is gadzooks and

> yuck!


We do both gas and oil but specialize in oil and hydronics. To tell the truth we really don't see a difference between cold start and maintaining from a service standpoint. But then pretty much all of our customers have us do an annual maintenance. Maybe that makes a difference. And we don't have many maintaining boilers. I'll make an effort to track them and see if we find a difference.

> JMO, but if the city water is not full

> of potasium, lime, whatever, the two coils will

> muck up at about the same time. As we know the

> tankless is easier to clean, IMO, with acids or

> shocking. Most indirects require pulling the coil

> and that ain't no fun.


Frankly, I'm not going to have my guys clean any coil with acid. It's a nasty, dangerous job. I know it can happen but so far we haven't seen an indirect coil limed up. I imagine that because the fresh water is on the outside of the coil rather than the inside.

> One other thing on the

> service vs. install thing. Installers have an

> easier time WIRING cold-start over many DHW

> installs, that's according to a lot of guys I

> have taught. To me, I never saw a difference,

> might be the controls???


I can buy this one. It seems one of the toughest things for any tech is wiring. Particularly low voltage. We generally use indirect water heaters and always prioritize them often using a small 24V relay. It takes most guys several times before wiring these becomes easy.

Firedragon_4

Aha, one out of three, I'm getting better :-)

With annual tune-ups the difference can be slight if everyone is usng instruments, etc. etc. When you go more than that it becomes quite visable and that's what changed my mind. Everything is relative.

Not crazy about acid either, but you do what you have to do. The water is everything in this equation. Most big cities are pretty good, then it gets worse all the way down to the on-site well system. If you're a big city guy like me, than you haven't seen it all. Get out, look around more often ;-).

Not only are you right about the wiring, but the multi-zone panels can make it brainless. Even more reason why I like warm-start. Try one, it's amazing.

Keep in mind that when that indirect circ comes on you're not pumping warm boiler water, but cold!

Ron Schroeder_3

Probably the worst thing that you can do to a boiler is to warm start it with the low limit set too low. If the boiler spends a lot of time between 100 and 120 degrees, you will get that gummy residue in the boiler. Either keep the boiler above 120 ~ 130 or cold start it. I don't reccomend running it it between.

Personally, I like to run warm start with 130 degree minimum boiler temperature in the winter and cold start with low limit circulator control in the summer.

Ron

Weezbo

Partial reset....

they can place that cheap cold start anywhere buh on one of my boilers...i must explain this over an over Thats mainly why i dislike the Weil mclains dont even send one to alaska ...i do my level best to not purchase them these days. i only install them under duress anymore.there is no credit given for the control against a new triaquastat, that right there should give you a hint as to what they think that things worth.

Steve_35

> no credit given for the control against a new

> triaquastat, that right there should give you a

> hint as to what they think that things worth.




Do they give you a credit if you want a different circ other than the one they supply? How about if you want a different gas valve? My guess is they don't give a credit for ANY part you want changed. But then I've been wrong before and probably will be again.

Weezbo

Wow How blind i am to the truth these days....

you say you have a coil and a triaquastat well, take the coil back get a plate and well and gasket, replace theplate and well put the tri aqua stat back in,set the low limit at like 145 first then the upper limit at like 170 reconnect the wiring done deal! all is well and hey ! they may take back the coil! that they used to do ...not that that is any consulation for the time however eh it was a way to at least get a functional tri aquastat with a boiler

tommyoil

Bill

Am I mistaken to think that this procedure is in the manufacturer instructions? I could swear I read it in their instruction sheet?? Just wondering.

Bill Nye_2

Ok so it is

Tommy it probably is......I'm sure it is, ... I read it too ... right about where it says only trained technician who are familiar with this should do it.

Ever see Dirty Harry? " A man's gotta know his limitations" Some people should mess with stuff, and some shouldn't and I guess it is not up to me to judge who should and who should not.

Pretty much if you gotta ask, you may be in over your head. But there is hope. If you don't ask, and plow right in, there could be trouble. A little bit of knowledge is dangerous.

I have been working with oil burners and controls for more than half my adult life. I have made some mistakes and learned from them. MOSTLY I learn from other peoples mistakes. When you work for a large oil company you get in a lot of basements. I have seen every type of miswired , missapplied and ill conceived control strategy there is. If I haven't seen it, a co-worker has and shared the info. Ignorance is in abundance so I am sure I haven't seen it all.

So, I am hesistant to suggest wiring short cuts to people who I have not worked with or know their abilities. I have fixed my share of circuit boards and Rube Goldberged many a control to prevent buildings from freezing in extreme weather, but there is no substitute for the correct part, correctly applied.

I am just an ignorant hill-billy red neck plumber so I tend to be very opinionated, but the technician side of me is very open to new and better ideas and methods. I just don't like cold start.

I just don't like cold start!! Maybe a new boiler, maybe. But that lousy 8148 is just a high limit! It has no reverse acting aquastat. We have to get a little smarter. Buderus and viessmann all have secondary high limits built in. {except the new cheap Viessmann]

If you have never been in a basement with an old Arco-liner or similar 50-60's era boiler and have actually waited 30 -45 minutes for it to make steam! You can hear the condensation sizzling off the cast iron. Plugged boilers? You should see what happens when joe smart @#! with the tankless coil shut his boiler on and off on a daily basis during the summer. You haven't got a clue. Cold start, it's not for everybody. I cold start my Viessmann but it has 3" of insulation wrapped around it, so it never really cools off. It maintains 95° I think, if the outdoor air is below WWSD. So I'm a flaming a#@hole, I can live with that. I've been called worse. At least I stand up to what I believe in.