I already have another question for the gurus out there.

I have been studying and monitoring my system but something seems off about it.

Here are the main components:
* Taco 705-2 Mixing Control / Outdoor reset with Outdoor Sensor, Supply Sensor and Boiler Sensor
* 1 boiler pump
* 1 injection pump
* 1 Taco SR506-EXP for the following:
* 3 pumps for radiant circuits
* 2 pumps for high temp baseboard circuits
* 1 pump for DHW

Here is the manual for this control: [URL=http://www.taco-hvac.com/uploads/FileLibrary/PC_705-2_(102-098).pdf]http://www.taco-hvac.com/uploads/FileLibrary/PC_705-2_(102-098).pdf[/URL]

My system is similar to Drawing 2 and 3 on pages 6 and 7 of this manual.

However,my system differs in the following ways.

1. My installer installed the boiler pump upon exiting the boiler, prior to the high temp circulators. This seems odd since this boiler pump is only on when there is a mixing demand. Do these circulator pumps allow flow through when off? If not, how will the high temp circulators create a flow through the boiler when the boiler pump is off? Is this a problem?

2. Drawing 3 on page 7 shows a PC705-2 (mixing control) controlling the radiant loops and a PC700-2 (boiler reset) controlling the high temp loops. Are seperate controls required with a mixed system (radiant + high temp)?

3. There seems to be no check valve on the return side of the high temp loop.

Ultimately, it seems like my boiler is constantly shutting down through the boiler aquastat (set to 190 degrees) even though I have high temp zones calling for heat. It almost seems like these high temp zones are only able to circulate through the boiler when the burner is on. If there is no mixing demand, it seems like the high temp zones are not circulating through the boiler, rather, they are circulating through a close loop through the Tees near the injection circuit.

It also seems like my boiler takes longer than normal to cool down, even when high temp zones are circulating. I imagine this may be because my high temp circuits are not flowing through the boiler when there is no mixing demand for the radiant loop.

I know I'm rambling. I wish I could post a diagram to explain better.

Any thoughts?

You are right a drawing would help

Generally if you have a primary secondary piping arrangment you need to have the primary loop pump operate when any of the zone pumps call. this includes the mixed as well as high temperature loops.

Sometimes an indirect is piped off as a paralel loop, and in this case the boiler or primary loop pump would not have to run.

There are lots of ways to pipe hydronic systems. We would need to see a drawing including check valve locations, etc.

Hopefully, soon, we will be able to post pic at this site??

It is possible for the boiler to shut off on high temperature with a zone or load calling if this load is smaller than the boiler output.

Fairly common, in fact, unless you have a modulating boiler.

hr

I managed to borrow some space on my company's website to store some drawings.

In doing some quick comparisons, it seems the Taco 700-2 is identical to the Tekmar 256 and the Taco 705-2 is identical to the Tekmar 356. I guess Tekmar must make these controls for Taco.

In reading Tekmar's application brochures and manuals, it seems that you would need both the 256 and 356 in combination for a system with both mixed zones and boiler zones. It seems like just the 356 would not be enough in this case. Is this correct?

Please refer to these PDF drawings with notes for a better explanation of what I'm referring to in my first post. You will need Adobe Acrobat 6.0 or later.

http://www.highwaytech.com/downloads/tacodrawing2.pdf

http://www.highwaytech.com/downloads/tacodrawing3.pdf


The Taco 705-2 variable speed injection mixing control manual can be viewed at the following link:
[URL=http://www.taco-hvac.com/uploads/FileLibrary/PC_705-2_(102-098).pdf]http://www.taco-hvac.com/uploads/FileLibrary/PC_705-2_(102-098).pdf[/URL]

The Taco 700-2 boiler reset control manual can be viewed at the following link:
[URL=http://www.taco-hvac.com/uploads/FileLibrary/PC700-2(102-097).pdf]http://www.taco-hvac.com/uploads/FileLibrary/PC700-2(102-097).pdf[/URL]

I hope this helps.

Thank You


[This message has been edited by neophyte (edited 02-17-2005).]

[This message has been edited by neophyte (edited 02-17-2005).]

[This message has been edited by neophyte (edited 02-17-2005).]

[This message has been edited by neophyte (edited 02-17-2005).]

[This message has been edited by neophyte (edited 02-17-2005).]

[This message has been edited by neophyte (edited 02-17-2005).]

Is the high temperature pump piped exactly as the DHW is in this diagram? If so it is not a secondary loop from the boiler (primary) loop. It is in paralel. Yes it does need check valve protection on BOTH lines, as shown.

Same with the DHW. Typically when a DHW loop is piped that way it has priority which shuts down the boiler loop pump, allows all flow from the boiler to the indirect for quick recovery.

Also the boiler pump in that diagram MUST run when the low temperature VS mixed zones are calling. Those closely spaced tees need flow, and higher temperature across them to make it all work.

If the piping is the same for the high temperature as the DHW, I'm not sure that would work properly, need to see more info.

Mike at tekmar, who's drawings you are actually looking at, regardless of the OEM name is an expert at this. Very helpful and easy to talk to. Fax or e-mail him and an EXACT actual piping drawing. It may need a minor pipe reconfigure to correct.

hr

The high temps are piped the same as the DHW. The second drawing, "tacodrawing3.pdf", actually depicts the way my high temp pumps are piped. I believe the Grundfos pumps that my installer used have built in check valves.

In terms of the DHW priority, it would be a bad thing if it shut down the boiler pump the way it is currently piped. I guess I need to have my installer move the boiler pump after the high temp pumps and add a check valve to the return feed.

Also, after reading more about these controls, I'm almost convinced I need both controls for my mixed system. I think the Tekmar 356 can only be used for a low temp system with just one high temp priority zone (DHW). I think the Tekmar 356 must be used in conjunction with the Tekmar 256 if I have multiple high temp loops.

I need to approach my installer with this information but I want to make sure I'm on the right track before I do so. I just wish my installers could get this stuff right the first time around without me having to do this research.



[This message has been edited by neophyte (edited 02-17-2005).]

I had a local radiant company do an inspection on my system. They confirmed some of my suspicions and then some.

My installer put the boiler pump in series with the high temp loops instead of in parallel as it should be. He also had it wired wrong so it was only coming on when the burner was running. It should be on any time there is a mixing demand.

There were some problems with the injection circuit as well. All but three of the pipe lengths pre/post the "T" fittings were far too short and did not follow the rules of injection piping. They were supposed to be 9" but three of them were only about 1".

He also had a check valve in the injection pump and on the return side of the injection circuit. From what I was told, this is not a good thing at the lower pump speeds.

Finally, I contacted Mike at Tekmar, as HR suggested, about the controls. He confirmed my suspicions on this one as well. He said the Taco PC705-2 (tekmar 356) cannot be used by itself on my system. It must be used in conjunction with the Taco PC700-2 (tekmar 256). As is wired, any time the high temp loops are calling, it will cause an injection demand when it is not required.

There were other items as well. It's amazing how these little things can so greatly effect the operation of the system.

Most of these things can be fixed relatively easily. Hopefully, my installer owns up to them.

[This message has been edited by neophyte (edited 02-25-2005).]

I outlined all of the above points, plus a few more, in a letter to my contractor. Several days later he called me back and agreed with all of them. He is coming by next week to correct everything and make it right.

All contractors make mistakes. The real test of a contractor is how they deal with them.