re-using 1955 cast iron baseboards

loueber

Hi guys. Hope you can give me a bit of in sight.
So, here is my dilemma. I purchase a 1957 ranch house in Boston. 1 level. Full basement. It currently has the original Cast iron baseray baseboards. The natural gas boiler is from the 90s (was an original oil boiler). The house is one large plumbing circuit with the outputs ( sorry for not knowing the exact term) that goes to each baseboard in each room. The system has one water circulator at the boiler outlet. Looks like mid 2000s circulator. The system currently works. However, I am rehabbing the house and will be changing the boiler to a 95 to 97% efficient unit soon. I would LIKE to keep the CI base boards because I am assuming they are more efficient tham copper aluminum finned baseboards?. ( plus I like the nostalgic look of them.)
Ill be doing most of the plumbing work myself, and will leave the main boiler replacement to you guys, the pros, for install. But here is my questions.
I want to zone different areas on zones.. Im never in the bedroom until night time. And the bathroom doesn’t need to be very warm. Nor the kitchen unless its dinner time.
This is what I was thinking to do IF I had copper aluminum base boards. But not sure if it would be the same for CI base boards.
Run pex tubing from the basement furnace to each individual zone. Zone 1- master bedroom and Mas Bath. Zone 2- second bedroom and second bath ( or no bath at all. It’s a small bathroom) zone 3 living room and dining room, zone 4 kitchen (using under counter kick panels perhaps?) zone 5 for basement one day. Each zone will have its own circulator pump.
Is this a feasible scheme? Or since im using CI baseboards do I need something special, like lower rpm circulator pumps? Or a special thermostat since I want to use a high efficiency new boiler? the house has a great insulated attic, and when i gut to the studs ill be insulating the walls.
The only reason im doing all the plumbing work myself is money constraints. But ill need a pro to install the furnace and do the final hook up to the pex etc.
Any thoughts?
Thanks
Louie

Jamie Hall

No reason at all not to use the CI baseboards. Also, not particular reason why you can't zone them and plumb them as home run or reverse return or whatever. Should work fine. You may need different pumps...

Ironman

If you install a mod/con (95% efficient) boiler, it will be low mass and will short cycle if divided up into too many or too small zones. Short cycling will reduce the efficiency and put the boiler in an early grave.

Your current boiler is high mass and can tolerate zoning much better. I'm not saying you shouldn't go with a mod/con, but I am saying don't zone the system up so much.

Hydronic heat is slow response and setting the temp back a few degrees in some rooms will produce very little energy savings.

If you go with a mod/con, get someone who really knows hydronics and have them setup the outdoor reset curve correctly. You'll get far more savings AND better comfort from that vs. zoning.

Also, make sure you use O2 barrier heating pex, not plumbing pex.

NY_Rob

Keep the cast iron radiators... they're the best by far!

By creating five "micro zones" you will probably cause your mod-con to "short cycle".... which is not good for efficiency or for the equipment.

If you're dead set on "micro zoning" each zone gets a zone valve not it's own circulator- you would need 5 zone valves, 5 thermostats and one circulator.
Maybe consider 2 zones vs. 5?

Mod-cons don't use setback, so no reason to keep a few rooms cooler when you're not home. You'll probably waste more energy trying to warm them when you want to then if you had just maintained them at the same temp as the rest of the house.
The other thing to keep in mind is that mod-cons heat with 140F or cooler water vs 180F water coming from your current system, so heating a cool room "on demand" like you want to do for your kitchen takes hours vs. min to get a few deg. temp rise.

j a_2

Couple things to consider
1 What about hot domestic water
2 how are current appliances vented
3 what is the gas pressure like in your area
4 can the new sidewall vented boiler be vented within the code

I agree zoning is not the best idea for your situation, yes People tend to like cooler bedrooms, but when accomplishing a heat loss we normally size up 20 percent..for bathrooms...

Me I would avoid the mod con, keep the cast iron, and skip the rebate issues

EBEBRATT-Ed

Cast Iron base board is the best so I would definitely keep those.

Most important is an accurate heat loss. Buy the smallest mod con you can that will provide the heat you need and a boiler with the best turn down. Install a large enough buffer tank to give the boiler decent run time without short cycling

loueber

Im so glad I reached out to you guys.
Read every ones reply. Thank you.
Again, its not that I think I can do everything myself, im simply on a very limited budget and the thoughts of running any new lins would save a bit of cash for me, and effort for the burner installer..
Sizing the unit, and the ultimate choice for mod/con or not will definitely be left up to a pro once everything else is done. but it seems that a mod/con may not be a best choice from what I read from you guys . it is a small house, and not the greatest insulated.
Your thoughts on having multi circulated zones for such a small house are well taken. Especially since its only a 1 level house. And the fact that the CI will take much longer to heat up really makes no sense to do so.
Continued thought: since the living room has the front door entrance, and the kitchen has the back door entrance, cold air would be rushing in, and those 2 rooms would have a faster heat loss then the bedrooms in the back. So, NY_Rob says to use “zone valves” and thermostat instead of circulators. Would putting the 2 bedrooms in the back which is away from the entrance doors be a good choice to have a zone valve for the bedrooms? This will break the system into basically 2 zones. And no longer 4 or 5 zones which I originally thought. Living room/kitchen zone 1 and bedrooms and baths zone 2. But ill be using zone valves instead (im assuming those are attached directly to the baseboard where there is currently an old fashioned knob on each baseboard. Which need to be replaced anyways cuz they are bit rotted. ) since it has such slow heat up time, and you mention there wouldn’t be much energy saving, my only reason now to zone the 2 bedrooms separate from the living room is the front and back doors.
Zone valves and thermostat would work ok for that?
The system looks like a “1 pipe” system. Not a reverse return 2 pipe. The main line has the break off line for each baseboard which connects back to the same main line after the baseboard. Seems like each room t’s off of the main circuit line.
Ironman mentions using 02 barrier pex.. BUT, if im not going to have multi zones, then I can simply keep the current steel main line, which has coper break out lines to the baseboards. since im going to use zone valves in the 2 bedrooms instead.
Considering JA’s thoughts…
1- domestic hotwater currently uses a separate boiler. But im replacing that with instant hot water system.
2- my current heating system vents directly into the cinderblock chimney in the center of the house. Its not a fireplace chimney, since the house has none. Its specifically for the furnace. Im guessing if I did not use mod/con, I can re-use the same venting right?
3- gas pressure? I have no idea. It was previously oil heat but was converted back in the 90s to gas when they ran the lines from the street.
4- not sure about code for sidewall vent either…I guess that would ultimately be determined by a pro. But, it seems that a mod/con may not be my best choice in my scenario from what im reading.

I appreciate everyone’s thoughts. It seems that ill leave all the piping the same, with the exception of putting the bedrooms on a separate zone valve so they wont heat up too much when the LR and Kitchen calls for heat when the front and back doors open and close. And everything else will stay the same except a new boiler, which i may not go with condensing. You guys are great.

NY_Rob

Lou, is this how you believe your current system is set up?

EBEBRATT-Ed

you can stay with a cast iron boiler vented into the same chimney. If the system heats well you can leave the piping as is and install thermostatic radiator valves in the bedrooms only to keep them cooler. This will save you some expense and with a small house it will work fine. What you have is a "one pipe monoflow system"

NY_Rob

If you do indeed have the system in the above diagram... that's great because as Ed mentioned above... just install Thermostatic Radiator Valves in the bedrooms and you're done! No need to repipe or install zone valves, etc...

Moving on to the boiler....

If you go with a mod-con, and plan to use the existing chimney you have to install a liner inside the chimney as the mod-con releases acidic condensate in it's exhaust that will damage the chimney over time. The liner will add about $1K to the cost of the job. If you can direct vent the mod-con through a sidewall, then no need to reline the chimney.

If you do go with a mod-con, then add an Indirect Water heater to it for your domestic hot water supply vs. an instant type water heater. Many of the pros here advise against installing the instant water heaters for many reasons, but if you are going with a mod-con the indirect tanks are a great fit for them.

bob_46

Louie if you look at the tees for each baseboard one of them should look different than the other . One may have a logo on it, those are monoflow tees. Its not a good idea to use any kind of valves on the baseboards. Anything that restricts flow through the baseboard adds to the pressure drop along the main and may cause downstream baseboards to have reduced flow. You mention old fashioned knobs, it would be interesting to see a picture of them.

j a_2

To OP what are you calling a instant water heater/?...Me I would go with a small pure pro boiler from f w Webb and a 40 gallon indirect...and call it a day...Can't talk costs but it's very much budget minded and will last a long time

loueber

Im on a lot of forums for many different topics, but I have to say this is the best and most informative out of all of them. I work in animal rescue, and also part time State work as an auditor, so needless to say I have to do a lot of things my self. I enjoy it though. SO.
NYRob,Yes, my system does indeed look identical to the diagram, utilizing baseboards though, that diagram is of radiators it seems. I know it doesn’t matter. Also, there is a longer feed line going from the main pipe to the bb. Not that that matters either. But its identical to that.
Bob, yes, the “t” on each outlet does indeed look different. the inlet to the bb side, is different then the t on the outlet side which connects back into the main line. ill get a picture of both this weekend. The way I understand it is that one of the t’s is some sort of venturi that balances out the pressure to keep the flow going? (Which now leads me to another question ill ask at the end of this post.) If those are monoflow ts, as you say, there still is however, valves at the inlet ( or outlet) of the bboards. I DO have a picture of the knobs! Im hoping that since there is a knob, and what I think the previous owner did, was adjust each room by opening or closing each individual knob. Which is what a thermostatic valve would do right?
J A, what I mean for instant water heater is either gas fired or electric instant tank-less hot water systems. Its only me and my fiance, and only one shower is used at a time. So I figured a medium instant hot water system would be sufficient instead of a separate 50 gallon tank water boiler that is there now.
Ok, so, things are looking good and it seems MY work will be minimal and potentially be just to install thermostatic valves if indeed they will work on my system. And have pro install either mod/con or not. I don’t want the extra expense of lining my chimney so unless I can have it installed on the wall, then id probably just sick with CI boiler.
Now, my other question that now comes up is this… assuming that the monoflow ts are utilized for pressure changes on the line… I may have another issue.
I plan on taking down a small wall between my kitchen and small den. Along the wall is a baseboard. I wanted to remove that baseboard, as well as the small one in my small bathroom. I planned on simply capping off the line that goes from the t to each bb. But im guessing doing that would change the pressure for the bbs down stream right? So for me to remove any baseboards, im guessing I need to remove both t’s, before and after the base board, and simply place a union in its place. Is that accurate?
Here is the picture of to valves on 2 different bbs in my house.

Ironman

Those are just shutoff valves, not TRVs.

Yes, you should remove the Monoflo Tees if you remove the BBs.

Also, you can forget about any zoning unless you re-pipe with separate mains.

As far as a CI boiler goes: you WILL still need a liner on new boiler due to its higher efficiency and lower flue gas temps. Wherever the chimney passes through an unconditioned space, the liner should also be insulated.

loueber

Can i simply replace the shut off valves with a TRV?
I guess it would be a good idea for a new liner anyways, since its built in 1957.

NY_Rob

loueber said:

I plan on taking down a small wall between my kitchen and small den. Along the wall is a baseboard. I wanted to remove that baseboard, as well as the small one in my small bathroom.

If you're removing the radiator in the bathroom.... it's going to get cold in there wintertime.

You also plan on removing radiator between the kitchen and den? How are you planning to make up for the loss of heat radiation in that area?

With 180F supply water (170F Avg. Water Temp) your cast iron baseboard radiates about 430BTU's per liner foot. Multiply the total length of sections you plan to remove by 430 to see how many less BTU's you'll have to do without.

Ironman

loueber said:

Can i simply replace the shut off valves with a TRV?
I guess it would be a good idea for a new liner anyways, since its built in 1957.

Simply, no. Is it possible? Yes, but probably more effort than you'll want. TRVs cannot be installed inside the radiator enclosure. You'd need ones with remote sensors.

Jamie Hall

On the TRVs. I'd be a bit wary. Unless the TRVs have the same or less head loss as the existing shutoff valves when they are open, even if they are open the water -- being lazy -- is going to go through the main line. Monoflo systems are sensitive to head loss in the side heating circuit.

loueber

NY_Rob said:

loueber said:

I plan on taking down a small wall between my kitchen and small den. Along the wall is a baseboard. I wanted to remove that baseboard, as well as the small one in my small bathroom.

If you're removing the radiator in the bathroom.... it's going to get cold in there wintertime.

You also plan on removing radiator between the kitchen and den? How are you planning to make up for the loss of heat radiation in that area?

With 180F supply water (170F Avg. Water Temp) your cast iron baseboard radiates about 430BTU's per liner foot. Multiply the total length of sections you plan to remove by 430 to see how many less BTU's you'll have to do without.

Its a very small bathroom. i will supplement with a small electric heater of some sort. To me, as long as the BR doesn't get below 50 degrees im ok with that lol.

so the wall between the kitchen and den is 10 feet. that has a baseboard ( that was the one in the picture that was white.) There is ALSO a baseboard that runs along the outer walls of that part of the kitchen, AND the outer wall of the den perimeter. Ill do the math as you suggest, but im guessing it may be fine since the outer walls all have BBs. 10 ft x 430 is 4300 but loss?

loueber

Jamie Hall said:

On the TRVs. I'd be a bit wary. Unless the TRVs have the same or less head loss as the existing shutoff valves when they are open, even if they are open the water -- being lazy -- is going to go through the main line. Monoflo systems are sensitive to head loss in the side heating circuit.

that would make sense, seeing how the water goes up to the BB via a simple diverter t. It probably would make sense to replace the shut off valves. i think in one room the knob is broke right off.

NY_Rob

loueber said:

...the wall between the kitchen and den is 10 feet. There is ALSO a baseboard that runs along the outer walls of that part of the kitchen, AND the outer wall of the den perimeter. Ill do the math as you suggest, but im guessing it may be fine since the outer walls all have BBs. 10 ft x 430 is 4300 but loss?

The loss of 4,300BTU's between two rooms in not insignificant.
Maybe some of the pros here will weigh in on that?