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Joined on December 29, 2008

Last Post on April 23, 2014

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Biggest Issue with ModCon's

@ December 15, 2013 8:00 AM in What is the most effective way to handle a MODCON

Here in the great USA. Fixed speed boiler pumps. They are the main cause of short cycling most of the time, the reason for elevated stack temps and high boiler return water temps when zoning.

Get variable speed boiler pumps controlled by the boilers logic to match its flow with the modulation rate of the boiler and they go away. The attached chart is provided by one mfg as the modulation rate in comparison to efficiency in its boiler. I don't know anyone else that publishes this.

Based On Other

@ December 14, 2013 3:51 PM in Triangle tube not reaching setpoint

Posts he has participated in its a PT110.


@ December 14, 2013 3:29 PM in Triangle tube not reaching setpoint

Its time to speed up that boiler pump. What the heat loss of each radiant zone and the baseboard zones?

Going back to your original post. Boiler supply 140 Return 108 - 32 Degree Delta-t

(Speed 1 Flow Rate is 6.5 or so x 32 x 500 = 104,000 btu/hr. Boiler Heating Capacity is 99,000 btu/hr. The 6.5 may be a little off, estimating off a graph.. I'd say the boiler is in high fire..

Deleted Duplicate

@ December 14, 2013 3:26 PM in Triangle tube not reaching setpoint

There's The Problem

@ December 14, 2013 11:14 AM in Triangle tube not reaching setpoint

Baseboard is on the last zone, slab is taking all the flow rate (ie, btu/hr) and the board zone is starving. Like I said 360 btu/hr per ft at that .5gpm flow rate - How many feet of board on that zone and is 360 x footage = btu/hr enough to get you to setpoint at design temp based on that zones heat loss?

Pull your triangle install manual page 82. On speed 2 the pump curve crosses the HX curve at at just about 9gpm.

I'm really Confused

@ December 14, 2013 8:44 AM in Triangle tube not reaching setpoint

You stated that you were piped pri/sec. With the slabs only running you state that the boiler supply and system supply are the same temp. That would mean your slabs alone are taking just about the entire capable flow rate provided by the boiler pump. The reason I know is that your boiler return water temp is elevated by 5 degrees above your system return based on the temps you posted when just the slabs are calling.

You then posted the numbers when both the baseboard zone and slabs are calling. Your again posted that the boiler supply and system supply are the same temp. The boiler pump is a fixed speed pump. The boiler pump cannot just create more flow. If the system needs more flow you would be mixing return water temp with boiler temp at the pri/sec tees and that water temp would not be the same as the boiler supply temp and you are posting that it is.

I ran the math, that slab is taking 6gpm. The boiler pump on speed 1 only provides a 6.5gpm flow rate. So your only moving .5gpm to the baseboard? IF that is the case the bb output at 150 degree water is only about 360 btu/hr per ft.

(B Flow Rate) - (S Flow Rate)*B Temp + (S Return Flow Rate)*SysRtnTemp/B Flow Rate = Boiler Return Temp

(6.5 - 6) *105 + (6 * 73)/6.5 = 89

Are the radiant slabs the first zones and the baseboard the last?

So a B2HA19

@ December 13, 2013 5:51 PM in Friday the 13th Boiler Failure

Is the better choice. Down to like 12 input.. Viessmann has a program for displays. Rather nice one.

Still Waiting

@ December 13, 2013 5:48 PM in Triangle tube not reaching setpoint

On the answer to my water temp questions. They are very important.

Didn't You

@ December 13, 2013 3:35 PM in Low-Loss Header: am I understanding this correctly?

Just have this boiler installed? Suggest you speak with your installing contractor. To answer your question. The boiler pump speed 2 and don't know what your gpm and head requirements are for the system side so can't tell you what speed to put the system pump at.

Why Not

@ December 13, 2013 3:31 PM in Friday the 13th Boiler Failure

A new 200? Turn down is way lower..

Taco I-Worx

@ December 13, 2013 11:34 AM in 6 Heaters - need one programmmable control

Simple out of the box stuff and can do it all from your office computer

Doesn't Matter

@ December 13, 2013 8:36 AM in Low-Loss Header: am I understanding this correctly?

You can run the boiler on a different delta-t then the system and in Viessmann's case you must since the max flow rate across the HX on the Vitodens 100 and 200's -19/26/28/35 is 6.2gpm

In the boiler control when you scroll the information via "I" button - Common Supply Temp is your low loss header temp.


@ December 12, 2013 3:34 PM in Triangle tube not reaching setpoint

I don't even want what the boiler is saying. I would like to know what the water temp is on the boiler supply entering the supply closely space tee and the boiler return back at the return closely spaced tee. Same goes for the system side. Water temps at the pri/sec point of boiler supply and return as well as system supply return.

You Didn't Need

@ December 12, 2013 3:32 PM in Variable Speed Pump with a low head loss system

To pipe with a low loss header. Could have piped direct. Since you did, best option for a system pump is a B&G Vario.

Your Missing

@ December 12, 2013 10:26 AM in Triangle tube not reaching setpoint

Things here. You are piped pri/sec must the info below

Boiler Supply Temp =
Boiler Return Temp =

System Supply Temp =
System Return Temp =

Let's Take This Slow

@ December 12, 2013 9:01 AM in Triangle tube not reaching setpoint

Boiler Supply Water Temp = ?
Boiler Return Water Temp = ?

System Supply Water Temp = ?
System Return Water Temp = ?

Your piped pri/sec so you should have 4 different temps unless the secondary side flow rate has exceeded the boiler flow rate. If that is the case then Boiler Return Water Temp would Equal System Return Water Temp. What type of pump are you using as a system pump?

Tell Him You Want

@ December 11, 2013 7:22 PM in Gas boiler choice

A ESC and call it a day.

What's The Size

@ December 9, 2013 6:30 PM in Navien ch 240

Of the home have to do with it. The question is, What is the hot water demand and what is the heat loss of the home. You know better HO1..

Different Times

@ December 6, 2013 1:23 PM in Gas Conversion Help.

Tim, agree with you but times are different. It also falls in with the PVC venting debate. Kind of the same thing isn't it?

HB Smith

@ December 6, 2013 10:48 AM in Gas Conversion Help.

Is approved for conversion since its offered with a gas power burner and has the testing. Will a gas conversion burner work when properly installed and set up. Sure will and very well. The issue comes down to liability. Not approved so the liability falls onto the contractor.

I'll Save You the Phone Call

@ December 6, 2013 7:48 AM in Gas Conversion Help.

Here will be their response.....NO!!! Installation Manual speaks for them. Been down this road many times. Also keep in mind that any warranty left on the cast iron will be voided.

Boiler Parameters?

@ December 4, 2013 6:40 PM in Navien ch 240

Not sure what you mean. My posting was really referring to the secondary side not the boiler/primary side and was at design conditions. Maybe I should have been clearer on that.

I'm surprised with the new unit they haven't incorporated a system side supply sensor to assist in overcoming the water temp drop that happens on the secondary/ system supply when piped with either their manifold kit, two closely spaced tees or a low loss header. In reality it doesn't matter what the boiler supply water temp is, it's the secondary side that needs to deliver to the emitter an x water temp not the boiler.

Homeowner, if you were referring to my post you are mistaken. I'm absolutely correct. Boiler only makes about 5gpm and if I need 12gpm on the system side the 7 has to come from the system side return. There are no Criss Angel's in the boiler room. Notice I didn't say anything about btu/hr and I didn't say you couldn't get more then 50K Btu/hr out into the system side. What I said was at what water temperature and that is critical.
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