Boiler not heating over 170 degrees

Ehbaseball025

Hello I just purchased a new home and the Burnham boiler 83WFH constantly runs, takes over 3 hours to make thermostat heat rise just 5 degrees. I noticed the boiler doesn’t go above 170/175 degrees. The aquastat high was 180 and low 160. I played with the hi/lo settings and same thing it constantly runs. The circulator, thermostat and burner are wired correctly in the aquastat. The thermostat turns the boiler on and off so I’m assuming that’s not the issue. Some radiators are getting hotter faster than others while some take hours to get Luke warm while the boiler constantly runs. The house has older 2  pipe steam radiators but I don’t think it’s steam anymore. The house has 9 radiators and the boiler makes the hot water. I appreciate any help thanks

SuperTech

Those are two pipe hot water radiators. You can raise the high limit,  but I don't think it would help. It looks like a lot of 3/4" copper used on the near boiler piping. You can only move so many BTUs in 3/4". The copper probably should be 1-1/4" up to the original distribution piping.  

hot_rod

The radiators are dictating the boilers operating condition, when you have more heat emitter than what the boiler can keep up with, the boiler may not reach setpoint.

Does the burner ever shut down? How long has it been running?
Did you do a heat load to see if the boiler has enough output?

Here is a snapshot explanation of thermal equilibrium.

pecmsg

Why is the expansion tank connected to the flow check? Cant say I've ever seen that!

Get a hanger on that tank

pecmsg

Agreed that near boiler piping needs a complete overhaul.
Water feed to the inlet of the circulator x-tank on the outlet?

What's the Spring loaded check and rubber hose?

Zman

5 degrees in 3 hours is a problem? Constant up and down temp setbacks work OK when used in scorched air systems. For an old high mass system, constantly fiddling with the temp may be costing you more money.

It looks like your circulator is a 007. Your system may distribute heat more evenly with a higher flow model like the 0010. You could also try partially closing the radiator valves that are heating quickly and try to manually balance the system a bit.
The 1" boiler piping is constipating the flow a bit, with those big pipes, you either need to finely tune the balancing or give it lots of flow to get even distribution

Ehbaseball025

@pecmsg the rubber hose is a bathroom addition. They installed another newer cast iron radiator in that bathroom 

Ehbaseball025

@Zman why doesn’t the boilers temp go higher than 175 when it ran non stop for over a hour. You would think the temp would keep rising but it didn’t 

pecmsg

Did you watch it for all that time?

Emitters have a higher output then the boilers input?

How accurate is that gauge?

There are several reasons.

SuperJ

Ehbaseball025 said:

@Zman why doesn’t the boilers temp go higher than 175 when it ran non stop for over a hour. You would think the temp would keep rising but it didn’t 

Think of it like a leaky bucket that leaks a bit faster the fuller it is.  Your radiators are big enough to get rid of the heat as fast as the boiler produces it at 175f. 

5 deg in 3 hours might be fine, sounds like your boiler is properly sized. 

Zman

SuperJ said:

Ehbaseball025 said:

@Zman why doesn’t the boilers temp go higher than 175 when it ran non stop for over a hour. You would think the temp would keep rising but it didn’t 

Think of it like a leaky bucket that leaks a bit faster the fuller it is.  Your radiators are big enough to get rid of the heat as fast as the boiler produces it at 175f. 

5 deg in 3 hours might be fine, sounds like your boiler is properly sized. 

Like he said....

Zman

My own heating system doesn't even increase the temp 1 degree per hour by design. It is more comfortable and efficient that way.

STEVEusaPA

If accurate your boiler gauge is reading 185 degrees.
Those aquastats aren’t always the most accurate at sensing proper temperature.
And your high and low settings may be too close together, not an actual 20 degree difference.
If i am interpreting your piping correctly, your boiler bypass is wide open.
Also, with the low limit so high, circulator is probably constantly cycling when recovering from set back

HVACNUT

Asking the pro's, Is that bypass piped correctly? Won't the circulator try to push both ways? Maybe close the bypass valve half way?
There are bleeders on all the rads. Loosen with a screwdriver or vent key and see it there's air. If there is, keep it open until its steady water.
We're assuming all radiator valves are open. CCW. 
Make sure the thermostat is perfectly level.
Set it to a comfortable temperature and leave it.
All things running correctly, it might be fine with a 160° limit.

Ehbaseball025

@STEVEusaPA please tell me what should my aquastat be set at?

Ehbaseball025

@HVACNUT should I release the air from the radiator when the system is running or off? Should I do this to every radiator?

SuperJ

My opinion on some of the near boiler piping.  

-the makeup appears to be on the wrong side of the pump.  It should be on the suction side along with the expansion tank.  Perhaps take the opportunity to move the pump to the supply side and install a micro bubble separator between the pump and boiler. 

-make sure the backflow preventer is ok to be mounted vertically.  

- I’m not a big fan of that bypass arrangement.  It appears to allow flow to go around the boiler.  This will increase the temperature delta on the boiler, and reduce the flow thru the boiler but won’t do anything to raise the return temperature on startup.  Better to use a thermostatic bypass. 

Jamie Hall

On the radiators -- and boiler -- reaching a particular temperature and then not moving even though the boiler keeps firing. The amount of heat the radiators can radiate increases quite a bit with increasing temperature. The amount of heat the boiler puts into the water doesn't. Therefore, at some temperature, the heat the radiators are dumping equals the heat the boiler can make -- and the temperature will stabilise.

Which assumes, however, that there is ore radiation than the boiler can power. Too big a boiler, and the boiler will have to switch on and off to allow the radiation to catch up. The aquastat keeps the boiler from getting too hot in case the radiation can't absorb all of the heat. The thermostat controls how warm the house is -- quite a different question.

EBEBRATT-Ed

Could be air bound radiation, but if the boiler runs all the time the heat is going somewhere.

You really need a good technician to go through the whole system

Did you try "find a contractor" on this site

hot_rod

And all that iron pipe is acting as a radiator, I'd bet you have more radiators and piping that you do boiler horsepower. If it runs 8 hours or an entire 24 hr and the burner never reaches the 180 or limit...
The near boiler piping, I agree, could use some massaging. Looks like you are pumping at the expansion tank, for one thing.

But that would not change the boiler to radiator mismatch.
as the building load increases with colder weather the boiler operating temperature may drop even more.

You could do a radiator assessment, or do a heat load calc and get a starting point, on paper.

The oil boys here could maybe tell you what that burner is capable of firing, with some data from you.

EdTheHeaterMan

It appears that this boiler is making hot water (DHW). Is that the only DHW Source? If yes then the temperature settings on the aquastat are proper. If there are times that you do not get sufficient hot water then the low limit may be increased. If you increase the low limit then you must also raise the Hi Lim accordingly.

Next. The boiler firing rate may be adjusted with a nozzle as small as .75 GPH up to 1.05 GPH which will also make a difference in the speed at which the water temperature increases.

Finally, the circulator is NOT operating any time the boiler temperature drops below 150° and it will stay off until the boiler temperature rises to 160°. The burner will continue to operate the whole time the circulator is off. (based on the 10° Diff setting) If you are not using this boiler for DHW then there are other changes I would recommend. So the boiler will not drop below 150° ever, even if the thermostat is turned down as low as you have it in the pictures. The check valve (on the rubber hose) and flow control valve (Green thing the expansion tank is attached to) will keep the heat in the boiler from entering the radiators unless the circulator operates That is the job of the low limit setting on the control.

The gauge temperature and the aquastat temperature settings may not be accurate. Allowing for "Kentucky Windage" if one is off +10° and the other is off -10° you may see a 20° inconsistency, which is not uncommon. And certainly not worth the hundreds of dollars needed to replace both.

The question you should ask is: Are you comfortable? AND Is there enough Hot Water? Then ask: Is the fuel bill affordable? If you answer YES to all three, then don't fix it. It ain't broke!

Someone may have tweaked this to the unusually difficult point of perfection.

On the other hand, If you answered NO to any of these questions, then describe the problem and we may be able to help. But don't go redesigning the piping and replacing parts if your system works

That is my humble opinion.

Ed

SuperTech

I'd definitely start with the easiest things. Check the radiators for air, with the system off. If you get water out of the air bleeder, the radiator is fine.  

fenkel

Agree with SuperTech..purge out any air in system.. are the valves to each radiator wide open or closed down?
Has the boiler had any yearly maintenance performed?

HomerJSmith

I would replace that old thermostat with a newer digital thermostat.

I would want to know if there is short cycling of the boiler. I know you said that the boiler runs constantly, but what does that mean? Is the burner constantly on and never shuts off?

Flow is the conveyor belt that carries heat energy to where you want it. With all the old large steam pipes, what happens is the water flow slows down going thru them which allows more heat energy to escape into the surrounding air leaving less btu's for where you want it, the radiators, as hot_rod said. You can insulate all the exposed piping to improve the btu's to the radiators.

You have a mixture of pipe sizes. The copper piping seems too small for the flow you need. I would have preferred a larger copper pipe size. All that pipe, fittings, and devices restrict the flow. I would remove any device that isn't needed. System Pressure Loss is the enemy of flow. To increase flow you need a larger pump, but the small copper pipes have a limit to the amount of flow that can go thru them. Too much flow and you get copper pipe erosion and noise.

If the boiler is firing constantly, that means that the flow is adequate and the water returning to the boiler is cold, below the differential. You may need to squeeze a few more btu's out of the boiler or you need a bigger boiler. If the boiler can't keep up with the btu's escaping the house envelop, you need more house heat emitters and a boiler that can supply that heat energy.

Return water to the boiler should be 130 deg at a minimum to prevent acidic flue condensation.

The point is, are you comfortable with the present configuration on the coldest day of winter. Hmm.

hot_rod

HomerJSmith said:

I would replace that old thermostat with a newer digital thermostat.

I would want to know if there is short cycling of the boiler. I know you said that the boiler runs constantly, but what does that mean? Is the burner constantly on and never shuts off?

Flow is the conveyor belt that carries heat energy to where you want it. With all the old large steam pipes, what happens is the water flow slows down going thru them which allows more heat energy to escape into the surrounding air leaving less btu's for where you want it, the radiators, as hot_rod said. You can insulate all the exposed piping to improve the btu's to the radiators.

You have a mixture of pipe sizes. The copper piping seems too small for the flow you need. I would have preferred a larger copper pipe size. All that pipe, fittings, and devices restrict the flow. I would remove any device that isn't needed. System Pressure Loss is the enemy of flow. To increase flow you need a larger pump, but the small copper pipes have a limit to the amount of flow that can go thru them. Too much flow and you get copper pipe erosion and noise.

If the boiler is firing constantly, that means that the flow is adequate and the water returning to the boiler is cold, below the differential. You may need to squeeze a few more btu's out of the boiler or you need a bigger boiler. If the boiler can't keep up with the btu's escaping the house envelop, you need more house heat emitters and a boiler that can supply that heat energy.

Return water to the boiler should be 130 deg at a minimum to prevent acidic flue condensation.

The point is, are you comfortable with the present configuration on the coldest day of winter. Hmm.

Possibly he has adequate radiation but not enough boiler HP, won't matter where you set the controls if the boiler is undersized? it's not gonna catch up, certainly not at design day if in fact the burner runs non stop now.

Looks like 1" copper piping, if so, plenty of size to move everything that 123K boiler can give. You can move 12- 13 gpm in 1" L copper.

unclejohn

Is the burner constantly running or is the pump constantly running.

EdTheHeaterMan

pecmsg said:

Agreed that near boiler piping needs a complete overhaul.
Water feed to the inlet of the circulator x-tank on the outlet?

HomerJSmith said:

I would replace that old thermostat with a newer digital thermostat...

...To increase flow you need a larger pump, but the small copper pipes have a limit to the amount of flow that can go thru them. Too much flow and you get copper pipe erosion and noise.

... You may need... to squeeze a few more btu's out of the boiler or you need a bigger boiler.

@Ehbaseball025, it appears that you need to spend lots of $$$

Be careful what you read here. There may be suggestions by others to spend your money on repairs and repiping that does not address your problem (assuming there even is a problem).

First, check the firing rate. You can do this by removing the nozzle line assembly and carefully cleaning the carbon off the nozzle to read the numbers on the flat surfaces (where you might put a wrench) to look for the firing rate stamped on the nozzle. Careful to not touch the orifice with anything. This could clog the nozzle or partially clog it and ruin the spray pattern. You just want to see the numbers to determine if you have a 0.75 GPH or a 1.00 GPH or something in-between. To be sure you would also need to check the fuel pressure to make sure it is set at 100 PSI or something higher (Check burner specifications). If you are not comfortable with DIY checking firing rate... Ask the service tech the next time your burner is serviced "What is the firing rate?".

Once you know the firing rate, you will know if there is room to increase the fire size to a higher (Hotter) firing rate.

hot_rod

as @EdTheHeaterMan suggested you need some stable data to solve this riddle. Starting with the actual available of BTUs from you boiler would be the best first step.

I would not change piping, pumping, controls, etc until you have some accurate boiler output data.

HomerJSmith

By the way, what is the temperature of the basement when everything is running for a while. Boiler rooms are warmer especially with uninsulated exposed piping. Why not put those Btu's to the radiators? Insulating those pipes are an inexpensive upgrade that I would do if it were me.

Zman

The position of the bypass valve may be part of the problem. You might try closing it a bit and seeing if it helps the circulation. If your return temps dips below 140, open it back up a bit.

SuperJ

Zman said:

The position of the bypass valve may be part of the problem. You might try closing it a bit and seeing if it helps the circulation. If your return temps dips below 140, open it back up a bit.

An issue with the bypass is that it's on the wrong side of the boiler circulator to do anything to warm up the return. It just allows the cold return temperatures to bypass the boiler, reducing flow thru the boiler, increasing the temperature delta on the boiler itself (but not the distribution).