Getting used to a cold start boiler.....are they really better/more efficient?

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Old 11-17-15, 05:10 PM
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Getting used to a cold start boiler.....are they really better/more efficient?

Hi everyone,
A few weeks ago I posted a thread about a boiler replacement at my grandmothers home to replace the 1957 American Standard gas boiler. Well now that the cold weather is here (well cold for a 98 year old anyway!), the new boiler is getting a workout. The new boiler is a Weil McLain CGA-4 gas boiler feeding radiators in each room.
My question is related to the "cold start" feature/function. I guess the old boiler always maintained a set temperature, so when the thermostat was raised the heat would come up very quickly. Now with the new boiler it takes much longer for the heat to start because the boiler needs to get up to temperature. It seems that the boiler drops down to about 75 degrees or so whe there is no call for heat. The upper limit of the range is 180 degrees. I don't know at what exact temperature the radiators start to get warm, but it does take some time from 75 degrees.
I assume that in the dead of winter the boiler will never have a chance to ever drop to a very low temperature because the calls for heat will be more frequent. So in the dead of winter the the heat response will, I assume be more "instant "?
So is the cold start feature that much more efficient since the boiler needs to jump so many degrees to produce heat, as opposed to being at the ready to send heat?
On the new boiler is there a way to have it NOT be cold start and always maintain temperature? If so, is that a valid idea? It will be interesting to see if any gas savings will be noted with the new boiler, hopefully there will be.

Thank you,
Zack
 
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Old 11-18-15, 04:31 AM
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The boiler is controlled by an aquastat. Can you provide the manufacturer and model number. It is usually different from the boiler manufacturer. This would help the viewers in answering your questions.
 
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Old 11-18-15, 04:48 AM
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A cold start boiler will actually use the thermostat as a form of indoor reset.
If the boiler is well sized to the house, it will slowly heat up the space and then shut off.

Warm start boilers tend to throw a bunch of hot water at the rads, then the return water will cool down the boiler and the process can then restart the whole system if the boiler temp get below the low temp aquastat setting. This causes the circ pump to shut off so that the hot water coil (if equipped) does not loose too much temp.
Cold start saves a bunch of energy by longer run times and off time, less short cycling, combined with draft dampers and electronic ignition this can save some money in fuel.
Cold start systems do not exhibit the same room temp overshoot that a hot boiler does. This encourages longer run times, lower water temps and all round better system performance and room temp stability.
 
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Old 11-18-15, 05:00 AM
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Also, the boiler with radiators should of been piped with some sort of bypass.. Possibly you can take pics..

Or tell us if the boiler comes up to 180f on a call for heat? Or does it just sit there and struggle to get to temp.. ? Maybe hover around a lower temperature?
 
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Old 11-18-15, 06:28 AM
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Here is the original link where I spoke about the boiler replacemnet...... http://www.doityourself.com/forum/bo...as-boiler.html
It has pictures of the new set up.

In terms of the second question about it getting to 180, I am not sure what you are asking. When there is a call for heat and the boiler is in a "cold state" the boiler kicks on and starts to heat up. There is heat emanating from the radiators before it gets to 180, but at what exact boiler temperature the heat starts to come from radiators, I am not sure.
In terms of a bypass, can you tell from the picture if one exists? If you can't tell from the pictures, what can/should I look for to determine if one exists?
The only complaint that my mom (who lives there) has said is that it "seems" like you need to raise the thermostat higher than with the old boiler to get the house warm. Or that in her opinion that it seems to cool down in the house faster. But her input is just anecdotal.
 
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Old 11-18-15, 06:49 AM
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I dont see a boiler bypass.. The boiler may be struggling to get to temp..

[ATTACH=CONFIG]58984[/ATTACH]

Here is bypass link.

Comfort Calc



Bypass Piping
When installing a cast iron or steel boiler we need to protect the boiler if any of the following applications. If any of the following conditions do exist, the potential of premature boiler failure may occur due to thermal stress or corrosion from flue gas condensation (sweating).



1. When the boiler is smaller than the amount of radiation in the system.

Yes in your case

2. When there is any cast iron radiation in the system.

Yes in your case

3. If there is any radiant in floor heat in the system.

no

4. When the return water is cool enough to cause the boiler to condense and corrode.

Possibly/probably


5. If the water temperature in the boiler cannot get to an average boiler temperature of 140f in a reasonable amount of time.


Possibly/probably but we are not there.
 
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Old 11-18-15, 06:51 AM
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You have to watch the boiler on a call for heat and note the temps of the boiler. Let us know ...

The old boiler had more mass and possibly warm start as you stated so the issue did not rear its head...

[ATTACH=CONFIG]58985[/ATTACH]
 
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Old 11-18-15, 10:37 AM
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Ok well it's clear that the boiler was not installed properly since no bypass exists. I've just spend a good amount of time reading various things on line about bypass's and why they are needed. In fact the life of the boiler even depends on it.
I will call the people back and insist that they install a bypass.
One thing I don't understand is how does a bypass make the overall comfort in the house better as was pointed out in many different websites. The statement was made but no real explanation as to why comfort is increased.
 
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Old 11-18-15, 10:58 AM
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Also I don't have a specific time (in minutes) to report on how long the boiler takes to rise up in temperature, but I will say that it seems VERY long!
I wanted the family to keep the old boiler in place and just replace the circ pump, but they insisted on having a new boiler installed! I hope this situation is easy to rectify!
 
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Old 11-18-15, 06:36 PM
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Others will chime in but I would assume you need a boiler bypass opposed to a system by pass.

One thing I don't understand is how does a bypass make the overall comfort in the house better as was pointed out in many different websites. The statement was made but no real explanation as to why comfort is increased.

Because the boiler will come up to temperature properly and it will not take hours to heat the home. Basically you will feel it get hot and cold more often in the home when the boiler kicks on and off from the t stat..


What they will need to do is move the pump on your boiler higher.
Cut a tee below the pump.
From that tee tie into the supply above the temp gauge.

Dont forget two valves need to be added.
one on the bypass and one between the gauge and the tee on the supply side.

As shown here pic below...

( Then what you do is see how the boiler performs like that. Both valves open.. The bypass alone should fix the issue. But if the boiler still needs help you close the supply valve slightly to slow the flow through the boiler . This will cause the boiler temp to rise faster)

[ATTACH=CONFIG]59014[/ATTACH]
 
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Old 11-18-15, 06:42 PM
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Figure 16 page 23 here...

http://www.weil-mclain.com/en/assets...ilerManual.pdf


And gauges should be placed as shown. 4a,4b, and 8 ( 8 is the one thats there now but your piping should be done exactly as shown...
 
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Old 11-19-15, 05:13 AM
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Generally, warm start systems send out large quantities of very hot water.
One would think this would be good for comfort, but it's actually not. These large quantites of 180 F water will heat the rads up quickly, but since the water is so hot the rads then over heat the space due to their surface temp being higher than required for the given room and outdoor conditions.
Think if it this way, you have a corvette with a 800 HP engine. What happens when you put it in gear an put your foot into it to get up to 40 MPH ? Ince you hit 40 MPH you will always overshoot because you used to much power to get to that speed, now you have to let off the throttle completely to avoid a big ticket.
If you used less throttle to get up to 40 you could have lifted off and hit 40 MPH with out overshoot.
What happens when you add too much energy to something too fast ends in overshoot, where it exceeds the setpoint. This is then followed by undershoot because there has been an abscence of energy for too long.
The larger the mass if the heat emitter the bigger the overshoot and undershoot.
They make very sophisticated controls, called PID controllers that sense load rather than temperature to cycle the heat load.

Using a boiler bypass and cool start boiler will allow the thermostat to stop the energy before it gets too much overshoot. And eventually as the outdoor temp drops and the load of the house increases, the heat will stay on longer and longer and the over/undershoot will decrease to steady state.
 
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Old 11-19-15, 08:31 AM
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Well I spoke to the installer yesterday and I explained the problem.
I causally mentioned the bypass and he said it is not "really " need on a single zone system. He mentioned he would do a bypass but first he would try raising the boiler temperature.
Based upon what I have read and processed, raising the boiler temperature will not do a darn thing.
I have trust in the experts here and faith in the numerous bypass articles I have read online to know that a bypass is needed. I will push for the bypass. This problem needs to be rectified before the really cold weather sets in. If nothing else, I want to see the longevity of the new boiler extended as far as possible. I guess you can say at the moment I am not happy with the choice of installer
 
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Old 11-19-15, 09:10 AM
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I causally mentioned the bypass and he said it is not "really " need on a single zone system.
Really? Ask him to show you documentation stating that.

Then show him the install manual..

at the moment I am not happy with the choice of installer
Believe it or not there are many pros out there that are not even aware of bypasses or let alone follow manufactures install instructions on new piping schemes like primary secondary piping..

Page 24 here verifys why you need boiler bypass and not a system bypass..

Top right of page 24 where it says " DO NOT"...

http://www.weil-mclain.com/en/assets...ilerManual.pdf

He mentioned he would do a bypass but first he would try raising the boiler temperature.
Raising the temp will do nothing IMO. If the boiler is struggling to get up to temp whats raising the temp going to accomplish?

Radiators hold vast amounts of water.. Too much water for the boiler to heat.

As I said the new boiler has only 2.1 gallons of water . Page 65 above. Of course its going to struggle to heat up 50 plus gallons contained in your system piping. Hence why you need a bypass..


Also the boiler bypass is called the poormans outdoor rest.. Ideally, and others will mention it here, the ideal piping scheme is primary, secondary piping as shown on page 21..

But you may have a fat chance of them piping it like that...
 
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Old 11-19-15, 10:07 PM
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I wanted the family to keep the old boiler in place and just replace the circ pump, but they insisted on having a new boiler installed!
That is also the recommendation you received here. At least now you have the right to say, "I told you so!"

Heed well what Mike and the others state.
 
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Old 11-20-15, 02:53 PM
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Well the installer seems hell bent on avoiding doing the bypass.....
He called me today to say that he needs to check the "economy" setting knob on the boiler. He said "he may have forgotten to adjust it".
Is there any merit to "adjusting" this knob? What does the economy setting do? How does adjusting it effect boiler performance?

However I won't be satisfied until the proper bypass is installed. If I need to be a difficult customer, I will be. It's not like we got a really cheap price on this boiler, $4,800 seems to be the going rate anyway.
To say that I am frustrated would be an understatement!

Zack
 
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Old 11-20-15, 10:59 PM
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Well, of course the guy is resistant to adding the bypass as he will have to "eat" the cost of doing so. Stand firm, and if necessary threaten to sue on the grounds that he did NOT install the boiler in accordance with the manufacturer's instructions. There is NO way to compensate with any kind of control adjustment.
 
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Old 11-21-15, 05:24 AM
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That economy setting is a time delay is all.. Page 30 in the link below.. That will circulate the water before firing the boiler to try to get any remaining heat out of the boiler..

Do as Furd states below..
 
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Old 11-21-15, 08:49 AM
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I just timed the boiler it took 25 minutes to go from 73 degrees to 136 degrees. I gave up counting at that point. I guess that seems rather excessive I assume?
 
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Old 11-21-15, 11:18 AM
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I just timed the boiler it took 25 minutes to go from 73 degrees to 136 degrees. I gave up counting at that point. I guess that seems rather excessive I assume?
Yes.. .
 
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Old 11-22-15, 05:44 PM
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Can you say boiler bypass required? Of course you knew that was going to be the response. Make sure the bypass water flow is cold to hot. When he is done the water temp in the bypass should be the same as the return. If it is the same temp as the supply it is backward.
 
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Old 11-22-15, 06:36 PM
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Can you explain what you mean clearer? I want to make sure the guy does the bypass correctly.
I know this is a hard question to answer, but a bypass "should" solve these issues, and this does not point to an undersized boiler?

Thank you for all of your help!
I will hopefully get this situation on the right rack, thanks expert guidance!

Zack
 
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Old 11-22-15, 06:46 PM
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Bypass needs to be piped as the install manual shows as we discussed..

Now refresh my memory so I dont need to read..

The cga 4 is a 88k btu boiler.. ( probably over sized I bet)

Whats the sq ft of the home?

How many rads in the home? You need to measure a section from the rads and tell us how many sections per rad to determing heat output.

Are all rads the same type?
 
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Old 11-22-15, 07:12 PM
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Old 11-22-15, 07:20 PM
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The size of the house is 2,054 sq ft (according to zillow).

The home has 10 cast iron radiators and 1 baseboard heating the garage.
I will measure the length of each radiator tomorrow.
 
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Old 11-22-15, 07:42 PM
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A normally insulated home at 2100 sq ft would need about a 52K BTU boiler...

IMO you have more heat output in rads then needed..

You can probably heat the home with lower boiler temps.... BUT.. Lets see what you got..

And lower water temps do not mean your boiler struggling to make temp...
 
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Old 11-23-15, 05:24 PM
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a boiler bypass is NOT going to allow the system water temp to climb up any faster. That is a function of the boiler BTU load BTU and flow rate.
What a boiler bypass is going to do is allow the boiler to operate at a high average water temp, under less flow. The idea is to try to get most of the boiler out of temp range where the flue gas condenses.
with a house full of cast iron rads, it's not a question of if you need a bypass on a cast iron boiler. You NEED one. Will it kill your boiler in a few short years... NO

it will affect combustion, your chimney, and will likely build up lots of soot that todays tech's don't seem to know how to clean up. I would be more worried about a plugged heat exchanger, or eroded liner in the short term that a rusted thru core.
 
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Old 11-23-15, 05:29 PM
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I think I have been using the wrong terminology the entire time when describing the radiators....I have been saying that it has cast iron radiators. I think what I should be saying is that it has radiant radiators. These are the exact type of radiators that the house has.....Radiant Baseboard Radiator | U.S. Boiler Company

Was I wrong? Does this make a difference in how to proceed?
 
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Old 11-23-15, 07:37 PM
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They are cast iron radiators so nothing changes. For bypass piping see this link Comfort Calc
Scroll dow a bit to see bypass piping.
 
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Old 11-23-15, 08:17 PM
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think what I should be saying is that it has radiant radiators. These are the exact type of radiators that the house has.....Radiant Baseboard Radiator | U.S. Boiler Company

Was I wrong? Does this make a difference in how to proceed?
No!!!!!!!!.........................................................
 
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Old 12-19-15, 11:39 AM
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Update.....
I have been going back and fourth with the installer over the bypass, he not wanting to do. Well when I gave him the actual temperature numbers, he is going to be there next Saturday to do the bypass!

Today was the first real cold day we have had so far this season, and I had a chance to get the real numbers.

It took 1 hour and ten minutes for the boiler to reach 180 degrees from a cold start of 75 degrees.
When the boiler was at 180, the return water temperature was just barely 140 (closer to 138).
I hope the bypass cures this issue once and for all!

Thank you everyone, I will give another update next week.

Zack
 
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Old 12-19-15, 12:44 PM
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Let us know and take pics please...
 
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Old 12-19-15, 05:48 PM
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I would also wonder why a 40f delta-T in the system. Water moving a bit slow?
 
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Old 12-19-15, 06:17 PM
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Won't the bypass help/fix the Delta-T issue?
 
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Old 12-19-15, 06:39 PM
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Won't the bypass help/fix the Delta-T issue?
Yes.... ....................

Its a 007 taco pump right?

If you have delta tee issues after a 3 speed pump will improve that... worry about the boiler temps first....
 
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Old 12-19-15, 06:58 PM
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Yes it is a Taco 007 pump.
 
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Old 12-27-15, 02:30 PM
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Well the bypass is done according to the Weil-Mclain manual. What do you think of the job they did? Was it done properly? It was very warm today, so we could not tell much in terms of heating ability. I will let the pictures speak for themselves.......

Zack
 
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Old 12-27-15, 02:33 PM
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Here are a few more pictures.....
 
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Old 12-27-15, 03:55 PM
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Looks good. Are you throttling those valves for a reason? I would run it with all valves open. Let us know how the temps at the boiler do.


What did the guys say? Seems we may have taught them something huh!!!!
 
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Old 12-27-15, 06:08 PM
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I am glad it was finally done as the instruction manual stated. Yes, they were in awe of the bypass. They mentioned that it sounds like a great idea.
As far as throttling the valves, they did that because they were playing with the water temperature in an attempt to achieve the "valve adjustment" directions on page 22 of the manual.
I will basically be on my own here with respect to valve adjustment, so I would appreciate some pointers.
So you say I should open both valves fully? What impact will that have on the water temp? What is the ultimate goal in terms of adjusting the valves?
The bypass is interesting because it seems to go against the goal of raising the return water temp. In reality it actually lowers it a bit, right? The WM manual notes that it is acceptable if the temp drops (#2 on page 22 in the valve adjustment section)
I just really want to make sure my family is comfortable when the really cold weather gets here!
Thank you everyone for all the pointers, it is much appreciated!

Zack
 
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