Two proposals, different design


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Old 04-03-13, 02:23 PM
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Two proposals, different design

Have two proposals for the same 85% gas fired hot water boiler, with different design specs. The house has two Slant Fin baseboard zones, each about 75 feet. The cost is about the same and either contractor is OK with me.

It comes down to this choice:

1) Two Taco 007 pumps and a Taco SR502 controlling panel.

-or-

2) One Taco 007 pump and two Taco 557 valves.

Which would be better?
 
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Old 04-03-13, 04:42 PM
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Hi Sanders,

Which would be better?
Well... it's kinda like the chocolate vs vanilla, or Ford vs Chevy debate.

Either way will 'gitter done'. There isn't really a clear cut 'better'.

Running two pumps might arguably use a small amount more electricity. The 007 is a very reliable pump. If it did break down, replacement parts are about $75 for a new 'cartridge assembly'. If the pumps are installed with ISOLATION FLANGES (which you should insist on!) it will mean that pump repair can be done very quickly without having to drain the water from the system. It is something that a homeowner with some repair skills could accomplish DIY.

Zone valves are a bit less reliable than pumps. This isn't to say that you should shy away because of this, replacing a zone valve head is a 10 minute job that is easily DIY. Zone valve power heads are about $75 or so, same as the pump cartridge. The actual valve BODY rarely goes bad.

Why is the contractor suggesting the 557 series valve? This is a 'high head' heavy duty valve that is not necessary for residential applications. It won't 'last longer' because of this though. It costs about twice as much as the 572 valve which has the same basic specs. I believe that it uses the exact same power head.

The 557 is a ONE INCH valve. 99.99% of residential systems use THREE QUARTER inch valves. Is there a reason he is spec'ing one inch valves for your job?

Have either of the contractors performed a HEAT LOSS ESTIMATE of your home? Not just a GUESS, but an actual calculation?

Virtually EVERY boiler installed in the past is OVERSIZED for the heat load. At least twice as big as needed. Sometimes 3 or 4 times larger...

Tell us how many square feet your home is, and what make and model boiler (with BTUH rating if you know it) they are going to install.

Don't pull the trigger until you know that your boiler is not too large for the home, you will pay for the mistake for a LONG time!

Tell us WHY you are replacing the boiler also...

Please read this:

http://www.doityourself.com/forum/bo...nt-boiler.html

Also, know that you can perform your own heat loss estimate. An educated consumer ... you know the drill!

Read this:

http://www.doityourself.com/forum/bo...alculator.html

In a couple of hours you can do this yourself and know the heat loss of your home.
 
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Old 04-04-13, 06:25 AM
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To answer your questions, it's the smallest boiler in the series being chosen. I want it to keep the house warm when it's -5F with howling winds and, if anything, I'm thinking I'd want a bigger one but three installers all came in with about the same size system and I'll accept that. Two of three installers the utility recommended took house measurements, not to the inch, but enough for a basis. I'll accept that; it's not a complicated home.

One contractor proposed keeping the existing control system with the single pump and two zone valves, and probably just wrote the wrong item number. Not concerned. The pump is a few years old, one head is aged the other not. It works OK.

3) The other installer is telling me that one pump isn't enough to handle the load (two baseboard SlantFin zones, each about 75', first floor) which is what prompted my initial question. He's making me think I don't know what the system should be like - in his words "it's wrong". His proposal includes "... valves on the inlet and outlet sides of the components..." so I assume that means isolation valves.

I am replacing a circa 1983 boiler which visibly seeps from a cast iron joint when it's cold, and I don't want to rely on it.

The dilemma comes down to keeping the existing single pump design which has worked fine or switching to the two pump design I'm told it should have. I have conflicting professional opinions and don't know enough about it to make an educated decision. Compounding that, I don't know if design differences between the old and new boilers warrant the change in pump design. And that's not something that one can just click around online to learn about.

If both are acceptable, which is preferable or does it really not matter?

Thank you.
 
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Old 04-04-13, 09:28 AM
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You really need to answer these questions trooper asked.

Tell us how many square feet your home is, and what make and model boiler (with BTUH rating if you know it) they are going to install.
Additionally make and model of old boiler?

IMO I would go with one pump and two zones valves.

Going with an oversized boiler causes short cycling and wastes fuel. I did not look at your design temps but -5f seems extreme. I did a quick look up and saw 5f being the lowest for MA.

NJ is 10f and I cant remember last time it was that cold.22f was lowest this year.... 10f was in 2006 I believe for a week, but besides that I cant remember being below 20f. And if so its not for long... Few days max.
 
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Old 04-04-13, 10:08 AM
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design temp for Boston varies from 0F to 9F in different sources.
 
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Old 04-04-13, 12:45 PM
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In the first residential hydronic heating system I designed, almost forty years ago, I used Bell & Gossett zone valves. These had a "heat motor", essentially a little heater and a wax pellet to actuate the valve. I had nothing but trouble with these valves and soon replaced them with White-Rogers motorized valves. The W-R valves had a synchronous motor with limit stops that would turn 1/4 turn to open or close the flow, with the motor stopping via limit switches in either the open or closed position. These valves worked flawlessly for some thirty years as far as I know. (The house was torn down after the thirty year mark.) The only "problem" with the W-R valves is they required a three-wire thermostat, something not common today.

I've been retired eight years now and prior to that I spent over thirty years in the design, construction and operation of commercial and industrial boiler plants so I don't have a lot of information on what is currently used in the residential field. However, my experience with those B&G valves has forever soured me on heat motor actuated valves. I think that at least some of the Taco valves use a heat motor. The other big player in zone valves, Honeywell, uses a synchronous motor but unlike the W-R valves the Honeywell valves work against a spring and simply stall the motor when the valve is open. I don't like that practice either.

So my opinion would be to go with the zone pumps.
 
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Old 04-04-13, 12:50 PM
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It gets cold along the shore of the Assabet River, and sometimes the open wind is fierce. There have been sub-zero mornings in years gone by.

89MBH from a Burnam ES24-B. No specs one the existing boiler. There's about 1180 SF on one level, 9' ceilings, 11 windows, 2 bay windows, 3 outside doors (includes 1 to the unheated garage), 3" wall insulation, deep attic insulation, no basement insulation. Would like to add some heat to the basement someday, possibly sooner than later if the new boiler's a lot more insulated than the existing.
 
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Old 04-04-13, 12:51 PM
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Furd,

There are W-R 2 wire zone valves out there:

1361-102 - White Rodgers 1361-102 - 3/4" Sweat Zone Valve (Two Wire)

This valve also has a huge CV number and tiny EFP.

But as you I think I favor zone pumps for the sake of simplicity and reliability.
 
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Old 04-04-13, 01:31 PM
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Apples v. Apples

I'm facing a similar dilemma and when it comes down to it I think its just a matter of preference. Lots of folks will tell you that zone valves have developed over the years and are highly dependable. Others will tell you something totally different and that zone circulators are the way to go. At the end of the day I think it comes down to system design, in-that a poorly designed system will shorten the life of either option you pick.

I decided to go with zone circulators. The reason being is that in a zone-valve setup, the single pump and zone valves are constantly operating -- as with any machine, the more time it spends under a "load" the more maintenance it will require. Zone circulators allow you to have some system components rest when not needed.

Again, I'm not saying zone valves are the wrong way to go--I'm certainly no professional--simply suggesting that its a matter of taste.
 
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Old 04-04-13, 08:06 PM
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Obsessing over this too much, for a quick resolve....

For a quick resolve, with the new boiler, would a single 007 pump operate within an acceptable flow capacity for +/-150' of Slant Fin finned baseboard heat, or would two pumps work better sharing the load for that length?

Forget about the zone valve question for now. Choosing one or two pumps is the last choice and the controls can be done around that.

So, one or two? Or a coin flip?
 
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Old 04-04-13, 08:29 PM
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OK, you think we're obsessing too much, fine. Take the information you've gotten so far and make a decision then. We're unbiased without profit motive and are only trying to help you NOT make a mistake.

As I said in my first post, it comes down to Ford vs Chevy. Take your pick.

installer is telling me that one pump isn't enough to handle the load (two baseboard SlantFin zones, each about 75', first floor)
Total bullpoop.

He's making me think I don't know what the system should be like
I would shy from this contractor.

would a single 007 pump operate within an acceptable flow capacity
Yes. You said it yourself:

keeping the existing single pump design which has worked fine
 
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Old 04-04-13, 08:38 PM
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"OK, you think we're obsessing too much, fine."


No, no, a hundred times no. That's me obsessing too much, not those here. Very sorry if I got that across wrong, it's not at all what I meant.

I think you're right. I'll, as you put it, shy away from the contractor who claims what's there now is all wrong. It's worked fine and only his comments made me think it needs two pumps.

Thank you.
 
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Old 04-04-13, 09:11 PM
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That's me obsessing too much, not those here
Sanders, that's pretty funny! really! you don't think we're obsessive...

Do remember though, there's nothing inherently 'wrong' with two pumps. In many cases there are fine reasons to go with multiple pumps. From what you've told us, I simply didn't care for the way he presented his 'reasons' to you. People you hire should never insult your intelligence.
 
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Old 04-05-13, 08:19 PM
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Another reason or proper sizing a boiler. Had a job site that had chimney condensation issues. The boiler was gas, chimney lined and later insulated. When efficiency goes up stack temp goes down.
The chimney had 3 exposed walls outside. Condensed on every cycle.
The problem was the boiler was oversized. The runtime is 1.8 minutes on average. The boiler does not in enough to heat the upper chimney liner and it condenses.
Boiler got changed to proper size after a heat loss, dropped a 4" liner inside the new 5" liner. A funny thing happened after proper sized boiler got installed. Problem went away.

Another job site, boiler drastically short cycling, hard lockouts on temperature. Boiler was piped with wrong size pipes, wrong flow due to improper pump size, improper near boiler piping. Re-piping and new pump fixed all the above except short cycling. This boiler is a 500,000 btu for apartment building. This boiler can also be de-rated. It is now operating at 60% of input and running fine.

Might as well add my two cents on the pump vs zone valve argument. I could give a rats but about the electric use when the boiler sizing is wasting way more fuel that the amount of electric can affect. The problem that I have with separate pumps over one valves is the (cast iron) boilers have changed. They have gotten physically smaller. The ratio of water volume to flow, amount of cast iron plays a big role here. The new boilers smaller yet when properly sized, may end up with too much flow when sized with separate pumps. The older larger water volume boilers had more water which had less rapid temperature changes. Every boiler has a minimum and maximum water low. For cat iron boilers divide the DOE output by 10,000 to get the maximum low and half of that for the minimum flow.
 
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Old 04-06-13, 06:07 AM
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rbeck, with a proper p/s piping, adequate flow thru the boiler shouldn't be a problem attributed to recircs vs zone valves.
 
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Old 04-06-13, 02:37 PM
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That is correct as far as boiler flow goes if using p/s. Many systems are not p/s. Many systems have entirely too much low. If the heat loss is 60k and the boiler is say 60k. The boiler and system should have 6gpm. Use three pumps for three zones and your flow could easily be a 12 GPM system flow which means very low system delta-t.
 
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Old 04-07-13, 12:34 PM
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rbeck wrote "the new boilers smaller yet when properly sized, may end up with too much flow when sized with separate pumps. The older larger water volume boilers had more water which had less rapid temperature changes." which makes me flounder again.

If you were getting into a new cast iron boiler with 90k BTU output, with two zones would you recommend the one pump (for both zones) or two pump (one pump for each zone) design or something else? Each zone has about 75' of typical baseboard, there's nothing exceptional about the house and the electrical use doesn't matter.

The heat loss calculations were 62,082 and 66,600.

Is obtaining a ▲T of 20 ideal?
 
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Old 04-07-13, 04:31 PM
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The system would require a total low of 6.6 and the boiler can operate between 4.5 - 9 GPM. In this case you should be ok as long as the to pumps running together you exceed 9 GPM. Size the pumps properly and you should be OK. I would do zone valves but that is me. They have become much more dependable but always have lasted quite awhile. I also am not a fan of the heat motors. With proper flow rtes your delta-t will only be 20f at 180f water temp unless you your variable speed pump.
 
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Old 04-07-13, 06:36 PM
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Sounds good, thanks.

How can I determine gallon flow of a single speed Taco 007 pump serving 75' of finned baseboard on a first floor?

There will be about 8' of pipe leading to the beginning of the loop, and about 20' of pipe in the basement returning the water to the boiler.

I saw the chart showing head and have no idea what that means. Would be happy to decipher it but there was no key or explanation.

The installer should be handling this, I know, but am of the impression he just wants us to accept what he preaches and not explain everything. Glad there are places like this board for unbiased helpful information.
 
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Old 04-07-13, 08:03 PM
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Is that all the baseboard and only one zone? 75' is that cover or element?
75 x 600 = 47,000 btu's. that means the boiler should not be bigger than about 50,000 btu's. the proper size would even be smaller Shan a proper het loss is done. You stated the heat loss was 66,000. If that is the case and you only have 75' of radiation in the home it should never heat when winter hits. I see many many homeowners try to do their own heat loss and miss the mark. This is why I never suggest someone not familiar with heat losses doing their own. This is too big of an investment to mess it up. If you have two zones of 75' my apologies cause you are probably close.
If you only have a total of 75 ft of radiation in the home your heat output is about 47,000 which means the flow would be about 4.7 GPM for a system delta-t of 20f. That is 0.2 above the minimum the boiler should have. If your total is 75 ft I will assume that it is equal which I am sure it is not, it would be 23,500 btu's which is 2.3 GPM which is not enough flow for the boiler. So separate pumps would allow the boiler to operate better but wy over pump the zones which means a very small delta-t in the zone. This of course is based on the baseboard amount not a heat loss.
You asked about calculating flow, use the delta-t from the boiler. Measure supply and return temps and deduct the return from the supply.
Flow= DOE output btu/490*delta-t
Example.
Delta-T = 20f, boiler DOE output = 80k, 490 assuming plain water-no antifreeze
Flow = 80,000/490 * 20 (some use 500 to make math easier)
Flow = 80,000/9800
Flow = 6.6 GPM
Good for boiler low delta-t in system, worse if two zones.
 
 

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