New boiler and we're roasting, now what?

Jay_21

You guys are great--thank you. Here's what Ive figured out with your help

Im wondering one new thing....the pump shuts off with the burner...should it shut off seperately?

and in response to these good comments:

>R.Lowenstein:
Maybe there's a check valve built into the circulator

It's a Grundfos UP15-42FC, and I believe it has a builtin check valve, alas. But none on supply?

>Mr. Garson said:
[try] the Honeywell digital thermostats
get the check valves. Have them put on both the input and output

I will look into the TStat, sounds like a good partial solution!--Real fixes like an Ecomatic control are more than I can afford.

The CheckValve issue is still open, I know theres one on the return (in pump) but not supply.

maybe I can talk the installer into remedying this at least. Theyre a reputable company, around 60 years or so. But obviously they like installs but want to be done when its over...or blew the sizing and dont want to spend time on it.

>Mr. Litman said:
the old radiators had a 180° turning radiator balancing valves on them

I think so, though I haven't found one yet I can turn (frozen). Maybe I need to lift dumbells instead of being one!

Jay_21

New Boiler & now we're roasting. Now what?

Hi all!

I'd be grateful for any advice you all may have in how I should (and how you would) handle what may be a much oversized new boiler.

We had a new buderus 103K btu g124X installed last spring, replacing a 70 year old cast iron oil beast.

The company did a nice job, but now we're trying to get the thing adjusted they've all but disappeared. Mostly theyve suggested tweaking the anticipator or aquastat.

im wondering if its even realistic to make it work comfortably for us...

Some background: we began with 3 estimates, all for 105K BTU Weil-McLain CGa4's. I wasnt keen on WM (and all three bids were similarily priced), so I tried one more round.

Three estimates later I had one bid for a 96K BTU Burnham 204, one for a SlantFin S-90, and one for a Buderus g124X. The more I learned, all seemed to be excellent boilers from reputable installers at fair prices.

I should point out that only ONE installer walked around the house for sizing--(he was a WM guy, and came up with 105K). The rest just eyeballed it.

Here's were my reasoning got me in trouble. I figured that the buderus (103K) or Burnham (96K) would be sort of the "average" of all the bids. I liked what I learned about the Buderus, though both burnham and slantfin seem excellent as well. I went with Buderus.

Now we're terribly hot all the time. My wifes mad at me and I dont know what to do. It was no problem with the old boiler.

Details:
1200 sqft wood frame house, "fair" insulation. Minnesota, so pretty cold (-12F for heating calcs?)! Old Cast iron rads (I did an amateur calc--they equal 367 sq feet of cast iron radiation.)

The installer (by phone) first had me turn down aquastat from 180F and later down to 160, and then later 140F. Even in cold weather last year temp never got above 130 before we were so hot we turned down the TStat.

Thermostat (Honeywell T87) anticipator started at 3.5, now its down to 2. Still overshoots about 6 deg. tStats OK--I happen to have a spare new T87 and swapped it, same problem.

OK--so Im carrying on too long here. My questions are:

1)
In the massive experience of pros on this list, does the boiler sound correctly sized? I know you can only guess without seeing it, but Im sure you all have a gut feeling about it? If 103K is too much, how could anyone recommend even more (like the WeilMclains)?

2)
*If* it is wrong, how would you handle a mistake like this in your shop? Is a replacement ever done? My biggest problem is I cant get them to come out, sometimes they will offer phone advice but say "thats how modern boilers work, hot and not".

3)
If we cant get anywhere with the installers--Do we have any option as a kludge? Can we go farther with the aquastat or anticipator? Any other workarounds such as special valves or some sort of "throttle"?

Many thanks in advance, I know this is not really the type of thing to diagnose over the internet! I just want to be a more informed consumer, and try to be educated with info in my next call to the installer...I really just want to solve the problem, not make trouble.

jeff_51

where in Minnesota are you?

Dave Stroman

I really does not sound like a boiler problem. Even if the boiler was over sized, you should still have some sort of control over it. How many stats or zones do you have? Does the boiler also make domestic hot water?

Dave in Denver

jeff_51

sounds big to me

my house in twin cities is 1954 cape about the same size as yours and only 75,000 btu. Run the boiler at about 140 degrees. Is the T-stat level? T-87 still has mercury switch and needs to be level or will throw it out of wack pretty easily. ( if it has digital readout, then doesn't have mercury switch)

Maine Ken

That cast iron will heat up until the t-stat is satisfied BUT there are still a tremendous amount of btu's stored up inside the rads and just dying to get out. This overshoots the t-stat setting and creates wild temp swings. What did the Buderus replace? gravity system? What is your piping arrangement. Do you have a reset on this boiler??? Amazing how warm and cozy you can be with ci running only 100* water!!!!!

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Ted_9

Buderus

How can you say its oversized because its too hot? Doesnt the system have a thermostat hooked up? An oversized boiler will short cycle.

Do you have the R2107 controller?

Could the tstat or relay be stuck calling?

could you show us some pics of the piping?

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Weezbo

your home is very toasty *~/:)

however you need someone to lay some sound control stradgey in on its head and get it to level out i have a buddy or two in Minnesota, both of whom may be contacted through Wirsbo...either would be able to suggest a means of getting your home comfortable. if you are interested jot me an e-mail... it would be easier for some real person with some wire snips and a screwdriver " there, "than diagnose and make suggestions from a distance. trust me on this one. for every ten plumbers and contractors there are at Least 100 ways to bring it around to real...........with a picture of your system however we might be able to see something obvious and you may be able to dial it in yourself,Your call.

Jay_21

roasting details

Wow--great responses already, thank you!

1) In response to Maine Ken:
it replaced a closed gravity system (which was once an open system). No zones, no ecomatic controller-nothing fancy!

2) in response to Mr. Gregoriadis who said:

>How can you say its oversized because its too hot?
Well, correctly I guess I should say we're too hot!

>Do you have the R2107 controller?
No

>Could the tstat or relay be stuck calling?
no, swapped out a brand new T87, same problem. aquastat too.

>could you show us some pics of the piping?
Not much to be seen, just 2 supplies and two returns with a valve on a short vertical pipe joining them (whats that valve for?)

Mark Hunt

There is no check valve

on the system and you are getting gravity flow causing the over-shoot problem.

You need a check valve installed.

They probably installed a by-pass. That is what the short pipe joining the supply and return is.

Mark H

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Weezbo

that valve is a by pass

> Wow--great responses already, thank you!

>

> 1) In

> response to Maine Ken: it replaced a closed

> gravity system (which was once an open system).

> No zones, no ecomatic controller-nothing

> fancy!

>

> 2) in response to Mr. Gregoriadis who

> said:

>

> _How can you say its oversized because

> its too hot? Well, correctly I guess I should

> say we're too hot!

>

> _Do you have the R2107

> controller? No

>

> _Could the tstat or relay be

> stuck calling? no, swapped out a brand new T87,

> same problem. aquastat too.

>

> _could you show us

> some pics of the piping? Not much to be seen,

> just 2 supplies and two returns with a valve on a

> short vertical pipe joining them (whats that

> valve for?)

Ted_9

heating


Your install, in my opinion, is missing the point of the best features of Buderus. They should have sold you the R2107 for outdoor rest, piped the circulator on the supply and removed the bypass since the R2107 takes care of boiler protection. Also instead of you basic T87, you should have the Buderus BFU room sensor. This set up will take care of you comfort issues and save fuel.
This is what I would have sold you.

Now, about the boiler size: You need a professional heat loss done.

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Rich Lowenstein_3

Maybe there's a check valve built into the circulator; one can't tell from here. But temperature fluctuations are practically a standard feature of "bang bang" heating. If your new boiler has more BTU than the old boiler, it will get the radiators filled with hot water before the stat has had a chance to kick in, so this will make things worse.

Is it possible that the circulators are wired to run all the time? Is the water running all the time by some chance?

Weezbo

that valve is a by pass

however, the real meal deal would be to check against flow and tap the two plugged Ts and dial the boiler temps up a notch and the field down your return temp to the boiler in that strech will be a bit hotter to help protect the boiler ,this in turn will cool the water going back into the field mixing it as it were. that is a cheap fix with variable results. a signifigantly better plan would be to use a tempering valve out to the system and a modulating return valve in the by pass.

Maine Ken

From Heting Q&A:

Gravity conversions:


When is it a good time to convert a gravity hot water system to forced circulation?
A: Usually, when the gravity system slows down because of the corrosion which has taken place over the years. Those little nooks and crannies in the pipe slow the flow and stop the heat. The natural response is to raise the temperature to make the water circulate more quickly. But you can only push the temperature so far before you begin to ask for trouble. That's when it's time to convert the system to forced circulation.

Q: What does this involve?
A: You have to add a circulator and (usually) close the system to atmosphere. You'll also have to make some changes to the near-boiler piping.

Q: What changes?
A: The old boiler probably has two outlets and two inlets because the idea in those days was to get the greatest possible gravity-induced flow of water through the boiler. The more holes, the better the circulation. That piping looked like this.




When you add the new circulator, you won't need to use such big pipes coming and going out of the boiler. In fact, you'll want to reduce the size of your near-boiler piping to give the circulator something to "push" against.

Q: Why does the circulator need something to "push" against?
A: So it won't kick itself off on its internal overload protector. A circulator does its maximum work when there's little or no resistance to flow. In a gravity system, the large pipes can't offer much resistance.

Q: Will I still need those double inlets and outlets at the boiler?
A: No, and that's another reason you should rework the near-boiler piping. With two inlets and two outlets the pumped flow might short-circuit around the boiler without moving out into the system.

Q: Suppose I don't want to repipe the boiler?
A: You may have to use two circulators - one on each supply line.

Q: How will I know what size pipe to use on the new boiler?
A: A good rule of thumb is to take the largest pipe, divide it in half and then drop one size from that. That becomes the size of your new near-boiler piping. For instance, let's say the largest pipe is 2-1/2" (if there are two inlets and outlets, you only have to consider one of them). Divide that in half and to get 1-1/4". Now drop down one size to 1" and that's what you'll use all around your new boiler.

If your largest size happens to be two-inch, pipe your new boiler in 3/4". It will look odd, and it might make you feel uncomfortable, but it'll work. Different systems call for different piping techniques. One size doesn't fit all and a gravity conversion is definitely different from a brand-new, forced-circulation job.

Q: How do I size the circulator for a conversion job?
A: It's real easy with these jobs. You're looking for high flow at a relatively low head pressure. A good choice is a circulator similar to Bell & Gossett's Series 100.

Your goal is to move a lot of water around the system as quickly as possible against very little resistance to flow. This type of circulator does just that.

Q: Can't I use a small, water-lubricated circulator instead?
A: These are fine circulators for most modern, forced-circulation systems, but not the best choice here. You don't need to generate much head pressure on these conversion jobs because the pipes are enormous and the resistance to flow is almost nonexistent. Using a small, high-speed, wet-rotor circulator is a poor choice on a gravity conversion because it will do the exact opposite of what you're trying to accomplish.

Q: I'm not sure I understand the difference between flow and head pressure. Can you explain it?
A: Sure! Flow is the "train" on which heat travels. Flow "delivers the goods" to the radiators. Head is resistance to flow and it's important, too, but only in relation to flow.

Q: Well, then what determines the head pressure?
A: In general, the size of the pipes. The smaller the pipes, the greater the required pump head, and vice versa. Since gravity systems have very large pipes, there's no need for a high-head circulator. What you need is high flow.

Q: Where is the best place to install the circulator?
A: It's always best to put it on the supply side of the boiler, pumping away from the compression tank. Piped this way, the circulator will add its pressure to the system's fill pressure and make it easier to get the air out. The system will also run more quietly.

: What method should I use to size the replacement boiler?
A: You should size the replacement boiler based two things: an accurate heat loss calculation of the building, and an accurate measurement of the existing radiation. Don't settle for one or the other, check them both and compare.

Q: Why is this so important?
A: By checking both the heat loss and the radiation, you'll be able to calculate the proper design temperature for your converted system. Many old-timers oversized their radiators because the only radiation charts available at the time listed steam ratings. One square foot EDR in steam work will put out 240 Btu/hr. One square foot EDR in hot water work (based on an average water temperature of 170 degrees F) will put out 150 Btu/hr. This is because water at 170 degrees F is cooler than steam at 215 degrees F.

To compensate for the charts, the old-timers added 60 percent to their radiation sizing. This, as you can imagine, led to some hefty over-sizing.

Q: Is that a bad thing?
A: It can actually work out to be a good thing. If the radiators are oversized, you'll be able to run the system at a relatively low average water temperature. I've found that most conversion jobs run well at an average water temperature of 150 degrees F (in the New York City area), and that's on a day when the outside temperature reads zero! Lower boiler water temperatures mean lower fuel bills.


Q: Why is the average water temperature limited to 170 degrees F?
A: So the water won't flash to steam in the open attic tank. The old-timers sized their radiation to provide plenty of heat on the coldest day of the year with a maximum high limit of 180 degrees F at the boiler. The water would leave the boiler at 180 and return at about 160, giving them an average temperature of 170 F within the radiation.

Q: If I run the system with hotter water what will happen?
A: You'll probably overheat the people and raise their fuel bills.


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ScottMP

Good Call Mark

Someone looked at the old gravity set up and thought they did'nt need a flow-check with one zone.

All that cast iron is holding its heat and letting it slideout to the house. Buderus has a good mass of cast iron and its holding the heat well.

Tell those guys to come back and put in a flowcheck.

Then you can have a happy wife. Cause " When Mamma Happy ...EVERYBODY Happy ".

Scott

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Steve Garson_2

I have had great experience with the Honeywell digital thermostats with Intelligent Recovery. It senses how long it takes to heat the house compared against the heat loss from past heat cycles. It learns when to shut off the circulator. If the circulators need to be shut off ten minutes before the house gets up to temp because your radiators hold so much heat, it will.

First get the check valves. Have them put on both the input and output of the boiler. You'll be happy with your system in the end. Even if a bit oversized, it will do the job better than the old boiler.

Roger Litman

Balancing a gravity radiated home

The inclusion of a check valve will probably cure your problem and I'm sure that you will end up using an iron one as the copper ones sometimes don't have the mass to avoid gravity flow. But there is a strong chance that the old radiators had a 180° turning radiator balancing valves on them, so the problem will become one of balancing the rooms of the home. To do this after the check valve is installed, make sure that the valves in the cold rooms are completely open and shut the valves in the hot rooms about 50% of the way, the valve in the room with the thermostat should also be 50% closed. This will make the pump run longer and warm up the cold rooms, after a while(a day or two) you can then adjust these valves to fine tune the system. These valves have a small hole in the blocking part so that there will always be a little flow. If the handle on a valve keeps turning without stopping, then the handle has broken away from the balancing portion of the valve. If the valve turns more than 180° tyhen it is probably not the right type for a gravity heating system. It is better to try to balance at night as then you will not be fooled by incoming solar radiation.

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Dave Yates (PAH)

sizing

If you're continuing to overhead your home with 130F water during design conditions (-12F you mentioned), the boiler will be oversized.

With a check built into the circ, I'd recomend the outdoor reset control and the new stat.

In theory, a single-zone system with a boiler that doesn't maintain a set internal temp can get by without a check valve. We have quite a few operating in this manner, with cast iron boilers, operating this way. The residual heat continues to gently work its way up into the rooms, but an oversized boiler will skew the results.

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Mark Hunt

Check valve in pump


Yes, the FC pump has a check valve. But the way they piped in the by-pass gives makes the check valve obsolete.

The pump should have been on the supply side and the by-pass should have been on the suction side of the pump.

Mark H

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