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Replacing boiler question?

wrxz24wrxz24 Member Posts: 285
Hi all,

I am about to have my CI boiler replaced with a new TT wall hung.  I have a question about the size of the return piping.  For my current boiler, the return piping is an inch and a 1/4 and for the TT 110, the return is 1 inch.  My question is this, can I just keep the same near bolier piping 1 1/4 ( p & s) with 5 zones and reduce it to inch.  I also am adding a 1 inch dirt separator to the new piping. 

One of the zones is for my indirect.  I know the TT has a separate DHW hook up.  Do I just redo the piping to the indirect and eliminate that zone from the near boiler piping.  The near boiler piping is all black iron.  Thanks in advance 


  • Aaron_in_MaineAaron_in_Maine Member Posts: 313
    edited April 2013

    Yes the domestic needs to come off that tapping. Because the board shuts off the primary pump on a call for domestic. Been there done that. The 11/4 is fine I would do 1 inch for your primary loop.
    Aaron Hamilton Heating
    [email protected]
  • wrxz24wrxz24 Member Posts: 285
    A picture of primary

    So I should convert the black pipe to 1 inch or can I just reduce it.
  • HenryHenry Member Posts: 726
    Pipe vs Boiler pipe sizing

    This is the biggest mistake we encounter with mod-con boilers next to improper venting. Those that don't do the math mistakenly believe that the proper size is the boiler connection sizing. It is so far from the truth. Keep your 1 1/4 sizing including the same size strainer. You reduce only at the boiler connections.
  • wrxz24wrxz24 Member Posts: 285
    I already purchased a ..

    1 inch dirt separator...should I return it and get a 1and 1/4 one?
  • Paul48Paul48 Member Posts: 4,256

    Something doesn't seem right with the piping?
  • wrxz24wrxz24 Member Posts: 285
    I'm all ears...

    What doesn't seem right? I want this right before the new install. What questions should I ask the installer?
  • Paul48Paul48 Member Posts: 4,256

    I'm not seeing P/S. I see 3 zones pumped supply, and 3 pumped return off antlers?
  • wrxz24wrxz24 Member Posts: 285
    Here are more pics

    The upper pumps are for my radiant. The lower ones are the baseboard and indirect. Can anyone confirm that existing piping is correct/incorrect?
  • heatpro02920heatpro02920 Member Posts: 991
    edited April 2013
    Holy Upside down pictures Batman...

    So you have 6 or 7 zones? How many sq feet is this home? What is the BTU loss on the smallest zone?

    I would swap them circs for something with delta t {Bees if they are in spec with your needs}, and use an 15-55 as you primary pump {I am having great results with them on the TT's, my new go to tt pump setup is Alpha primary {110 has a 3 speed inside it you need rotated flange, I would just put a nipple and set of flanges and put the pump outside the cabinet}and BB secondaries, worx goo'ud, but I have only installed a pair of 60's a few 110s and a couple 175 {one in my home} no 250s or 399s as of yet}......

    Now as far as piping goes, just have the installer follow the manual and you should be in good shape {as long as there are no misprints, lol} I would put the pumps on the supply personally. Since you are going with a strainer maybe just jump into a and not worry about sizing, buy a 1 1/4 spiro therm and pipe it all 1 1/4.... Im starting to warm up to these....

    What are these zones going to? Radiant, heat coils, baseboard????

    I would have who ever pipes the system redo that, so all the pumps are on the supply, and get rid of that 3/4" return/supply bridge....

    If you let us know what they are going to we can let you know the best way to do it, maybe someone may even draw you a picture...

    Of course you will need some drains, I use dielectric unions, and isolation flanges on the circs, as well as make sure all other components are isolatable, if you are using an indirect the 110 has a separate port for its supply and then you will need check valves, plus checks in each zone if you are not using the internal or existing units...
  • Paul48Paul48 Member Posts: 4,256

    The TT can be pumped through like that, as opposed to P/S, provided any single zone meets the minimum flow requirements for the HX . The pumps on the return offer no advantage. How are you balancing the split loop?
  • heatpro02920heatpro02920 Member Posts: 991
    Im thinking with

    that many zones unless the houses is HUGE, they must be smaller, so I would think P/S piping over direct?
  • wrxz24wrxz24 Member Posts: 285
    edited April 2013
    House size

    Around 3400 sqft. This includes a zone for a bonus room above the garage and the garage floor is heated as well. The first floor of the house is all heated slab. The upstairs is baseboard. So including the indirect, I have 6 total zones. However, one of the zones is for my garage which I keep at a balmy 45degrees in the winter.

    Are you saying I should get rid of the 007 pumps?
  • heatpro02920heatpro02920 Member Posts: 991
    edited April 2013
    Since you are changing the boiler and repiping anyway

    I would go with bumble bees on the supply...

    I would need to see how your radiant was piped, it must be getting cooler water than the bb and indirect...

    OK, I did a similar install, the house was split between radiant and baseboard with an indirect... The first floor was radiant {retrofit} second was bb {couldnt retro because of ceilings}, they had 6 zones 3 radiant and 3 baseboard....

    I piped it with 2 circulators {alphas} and 6 sentry zone valves. 1 circ did the radiant with 3 zone valves and the other did the 3 baseboard loops.

    The wiring is where it gets different.... Instead of using a zvc-406 I used a zvc-403 on the low temp zones and a zvc-404 on the high temp zones, and I wired the end switches from each separately to the CH1 and CH2 circuits, I then connected the zvc-404s extra priority zone t-stat connection to the low temp zones endswitch and then onto the boilers ch2 circuit , so they don't call at the same time. So when a low temp zone calls the high temp relay is shut down on priority. So the result is the 2 panels can never call at the same time, because on the trimax control you can set up 2 separate curves allowing you to run one zone at 180 and one at 110 if you want.. BUT when they both call it will revert to 180 and overheat your radiant zones.. So wiring it this way stops that from happening... The downside is the 6 zones can never call at once... So I thought this may be a problem, but the house I installed it in had a heat loss of 67K and the 110 was a little over that... I thought they may have a problem with their second floor not getting heat because the first floor running constantly, in which I had a few ideas to fix it, but they never had an issue, the system warms the entire house, they actually said they noticed no temp differences... I told them {I know them pretty well, they go to our church} that it was experimental and if it caused a problem I would take care of it... But they like it, their programmable t-stats are set to actually turn down the first floor zones at night and turn the upstairs up... I had another trick up my sleeve if it did let the upstairs zones get too cold, I was going to make it so if the second zone called while the low temp was running it opened the zone valves and ran the circ but didnt close the end switch until the radiant was satisfied, so the base board would have at least gotten the low temp water... But heat rises, the house was well insulated and it worked out well, we had a cold winter with no complaints, I expected them to say it dropped a couple degrees here and there, but they said it never did...

    And as for the drawing above, it woul change because you have an indirect and low temp radiant... the indirect will be piped off of the primary loop and the 110 has a separate tapping for the indirects supply... you will also need a check valve in there...

    What is your actual zone count radiant and baseboard? and I am curious to how you are getting the cooler water to your radiant?
  • Paul48Paul48 Member Posts: 4,256

    I would consider combining your baseboard zones into one. I cringe when I hear someone say they have a single room as a zone. The boiler needs load to operate efficiently. Running on ODR it's not the kind of heat you are use to. It's just comfortable, even heat. Let the mod/con do its thing.
  • wrxz24wrxz24 Member Posts: 285
    1 zone is for main...

    The other is for 16 x 32 bonus room, that will be a lower temp setting. Thanks for all the advice, keep em coming.
  • heatpro02920heatpro02920 Member Posts: 991
    I agree Paul

    The days of a t-stat in every room are over, I like 1 zone per floor {or 1 zone for bedrooms and one for living space, some houses have special circumstances like guest rooms that are only used once a year, sun rooms, ect... My house has an 1100 sq ft guest suite with 2 bedrooms a parlor and full bath, obviously I zoned that off from the rest of the floor, no sense keeping it 70 year round when we use it for 2 months a year {mostly in the summer}.

    So OP what is the real zone breakdown 1 for indirect , 1 radiant slab garage, 1 radiant slab living space, and 3 baseboard?
  • Paul48Paul48 Member Posts: 4,256

    The goal is to provide just enough heat to the structure to compensate for the temperature outside.The whole structure becomes an emitter, of sorts. The more you chop the house up into different desired temperatures, the more you complicate control strategies, and sacrifice efficiency.You make the boiler short-cycle by running micro-zones.
  • wrxz24wrxz24 Member Posts: 285
    edited April 2013

    I have 2 zones on first floor. 34x 44 ft space. One zone does the master bedroom and bathroom (16x18 bedroom and 14x 10 bathroom. ) the other zone is for the kitchen dining, living, (breezeway which is 12x24) The other radiant zone is the garage floor(28x32) The upstairs has 2 zones, the 34 x 44 is all one zone and the bonus room the other(16x32).

    I have mixing valves for the radiant. Return water can go back to the system mixing with boiler water. The highest I go is 110 and lowest at 90 depending on the weather. I control these manually. The floor s 4 inch slab. I have a 12 degree drop on the radiant manifold. I have 180 degree supply and 140 return temp.

    I think I could go lower on the baseboard.
  • Paul48Paul48 Member Posts: 4,256
    Heat Loss

    What are the heat losses by zone?
  • wrxz24wrxz24 Member Posts: 285
    Not sure

    The whole structure has a 90k for -9 design temp and 68 indoor. This includes the garage which I will keep at 45-50. I have the info on my computer at home but I'm away so I can't tell you now.

    The problem with combining zones is that I like to keep my bedroom cooler than the rest of the house. The bonus room won't be used all the time. I was thinking of replacing just the two circulators for the largest zones that seem to run the most of the time. The main radiant and main baseboard seem to run the most, temp is set at 68 downstairs all winter and 66 upstairs.
  • Paul48Paul48 Member Posts: 4,256
    I was wondering

    I know most folks like their bedrooms cooler, but how does that work with the bath tied in? They are usually polar opposites as far as required temperature.
  • wrxz24wrxz24 Member Posts: 285
    edited April 2013
    Bathroom is tile

    So it is ok. The bedroom is Berber carpet and that is where the tstat is. The bathroom is pretty comfortable.

    So am I looking at tearing the old piping out and starting new or with some slight changes, can I replace my smith 150,000 btu boiler with the tt 110? The installer acted like it wouldn't require many changes. He is estimating for 14hrs start to finish.
  • Paul48Paul48 Member Posts: 4,256

    heatpro can speak about this, but I just don't see the need to be pumping all the zones in your situation. The garage is almost like an afterthought, and minimally heated. From your description, it's modern construction, as opposed to an old drafty house.You have 2 primary zones, with all the others lower temperature.
  • wrxz24wrxz24 Member Posts: 285
    So should I?

    Combine the downstairs into one zone and upstairs into one as well? Could I still have separate t stats? Keep the garage separate. If I wanted my bedroom cooler, I could keep the mixing valve at a low temp? The other mixing valve would be for protection if all zones were calling. Thanks again.
  • SWEISWEI Member Posts: 7,356
    combining zones

    properly involves careful consideration of occupancy patterns and sources of external heat.  For occupancy think guest rooms, workshops, etc. which are used infrequently.  For heat sources think solar gain, wood stoves, cook heat, or even large groups of people.  Any space which can receive heat from these is a candidate for a thermostat (as high limit device.)  Balancing valves are a must when merging existing zones - plan to add them if they are not already present.
  • heatpro02920heatpro02920 Member Posts: 991
    edited April 2013
    For master bath setups

    I always pipe the bathroom first with 20% more element than the bedroom{per area}, for example when I built my house, I have a hydro air that runs the master bed and bath, the bath has the same amount of duct terminations as the bedroom when the bedroom is 6 times the size of the bathroom, but there is so much stone in the bathroom and such a huge tub I guessed I would be about rite, and it works out, the bathroom is always a little warmer than the bedroom...

    For the op as far as your system it sounds like you need to get a good company out there and get some ideas, I hate to gues with out actually seeing what there for my self and performing heat losses and looking at layouts, there is a lot to it...

    I would go with a tt wall hung, and I would pipe it how I drew for you, but for your radiant zones, try to see if the contractor can do it with out using mixing valves. A separate control and plate exchanger could be an option with a 3 way valve letting you use return water...
  • wrxz24wrxz24 Member Posts: 285
    taco sr6 relay?

    Thanks again for all the advice.  one more question, i currently have a taco sr6 relay.  Can I use this when I swap out my 150,000 btu boiler with the TT 110?  Thanks in advance. 
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