Hey experts. I'm looking for your opinion on which boiler control is better. It'll be going on a biasi b-10/5 with a reillo f-5 burner. I have a smart 40 indirect hot water maker. Also I'm thinking of using the taco zone valve controller. Any thoughts? I want to use the boiler in a cold start mode with dhw priority
Thanks
greg

 

If you are giong to use the Taco ZVC then there is no question but to get a ZVC-EXP and use the PC700-2

 

i am no expert....just a homeowner but i just installed a very similar set up.
buderus g-215 with riello f-5 and an indirect for DHW.

i used the TACO EXP and pc 700-2....very simple to use and seems to be doing a great job.

i just added the post purge card which simply plugs onto the board of the EXP. very easy and user friendly.
good luck.

 

I looked hard at both. Decided on the tekmar 260. If you add the indoor sensor, it is really really good. Way better than the PC-700.

The guts of the PC-700 are made by tekmar.

Both are good.

 

Thanks for info. I'm still torn. the the pc-700 with the post purge card and the priority overide seam pretty comparable to the 260. I think they'll mate better with the zone valve controller. I think my biggest question is with the dhw priority. For the 260 it won't accept a zone for it. So I'd have to put in a second circ pump. Not that big of a deal but still an added expense.
xiphias what factors swayed you?

 

The reason I say use the PC 700, is because it is made to go with the ZVC EXP .......far less wiring headaches.......plug and play

 

Factors that swayed me:

-260 has more bells and whistles for DHW priority (e.g., priority length based on outdoor temperature -- if it's super cold out, then it won't let the building cool off too much).

-Does a good DHW post purge; also mixing purges depending on target supply temp, etc. that help get useful leftover BTUs into the DHW and the space heating.

-By the time you get the PC-700, the PC600 and PC605 cards, you are right there at the cost of a 260, and the PC-combo doesn't have all the functionality.

-The 260 can accept an indoor sensor. This _really_ makes this control sing by constantly tuning the supply temp to hold the indoor temp using the coolest-possible water. (Having the indoor sensor also seems to affect the DHW priority in a good way, because the sensor can actually see what happens to the building temp if there is a long DHW call.)


Notes.
At the time I bought the control, I was rather ignorant of whether the indoor sensor would gain me much. Did a bit of research and planning, and decided it would be a good thing. It's better than good. It's great. Inexpensive, too.

The PC700 is based on a reset ratio, which in theory is a lesser way of doing outdoor reset compared to tekmar's "characterized heating curves." In practice, at least in this house at the water temps it needs, there doesn't seem to be any difference. Also, with the indoor sensor, the reset curve is being constantly shifted to hold the indoor setpoint anyway.

I would not be at all concerned about interfacing the Taco ZVC to the 260. It's done a lot. I have a Taco SR connected to my 260. Works great.

Nor is there any downside to having a dedicated circ for the indirect DHW. Depending on what indirect, you might actually need a different circ anyway. There won't be any discernible difference in electrical use between 2 circs and 1, since when the DHW is on, the space heating is off.

If you do isolation flanges on the circs (and you should), if one or the other ever fails, you could just swap. For example, if the space heating circ fails at 2am on a Saturday, pull the indirect circ and put it in the space heating. You'll get through till you can get to the supply house for another circ.

These days, a circulator costs about the same as a good zone valve.

If this were my system, I'd do the ZVC and the 260, use zone valves on the space heating, and wire a dedicated circ for the indirect directly to the 260. And definitely figure out a good location for the indoor sensor. Got mine on feebay. Paid for itself in about 2-3 months due to lower water temperatures used across the board, reducing fuel use.

A big advantage of the indoor sensor is that you get an automatic boost to recover if you use an overnight setback. Not so with a "standard" reset curve approach where it might take many hours to recover a couple degrees.

There is another recent post on this forum that talks about potential ways to fake a 260 into thinking you have a pump but it's actually a zone valve, and thus get all the DHW priority features, etc. If you do go with all zone valves and the 260, check it out. It would probably work.

 

Thanks for the advice. You've swayed my I was leaning towards to taco just for added interoperability(big word for a fireman) but it sounds like that won't be a problem. My next question is what size circ pump do I need? I have a smart 40 for dhw. I got a deal on it cause there is a crack in the plastic!!!!
Thanks
Greg

 

The manual

http://www.triangletube.com/PDF/Ind_...t%20manual.pdf

says you want 7-9 gpm. You'll have to figure out the head loss of the piping between the boiler and the indirect, etc.

Taco 007 might do fine. Or the Taco 00-R 3 speed, or the Grundfos 15-58 3-speed.

 

You can zone the DHW with the 260, but you will lose the post purge feature by doing so. Examples are shown in the PDF file, available online, for the 260. Add the second circulator.

Pete

 

Pete, I agree that the 2nd circ for the indirect is the right way to go, but there may be a way to fake the tekmar into thinking a ZV is a circ. Speculated (and how!) on that here

http://forum.doityourself.com/showthread.php?t=348289