Adding a Radiator on a Gravity System in the Basement

TheUpNorthState88 · January 6

Hello everyone,

This has been an idea floating around in my head recently after realizing with the help of my new thermal imaging camera that the former piping that previously was connected to an indirect water heater to my boiler still gets hot. I’ve been wanting to find a permanent heating source for this half of my basement which includes my small workshop area and maybe a future “poor man’s man cave,” nothing fancy. Because of the radiator piping and the height of my basement, I could never finish the basement. I already have to duck my head to get around some of the pipes lol.

So here comes my question, is it possible to connect a cast iron rad to this former water heater connection seen in the photos below to my 1937 Ideal Boiler No. 7 (model: W-731-O)?

My boiler is in excellent operating condition (I pride myself in doing its care and maintenance myself) and it is not going anywhere anytime soon. What is drawing me to this so much is the fact I would NOT have to touch anything related to the piping to the rest of the house. It’s literally low hanging fruit and a direct connect to the boiler that’s simply capped off right now.

My home is heated fully by its original gravity hot water system (home built 1909). No circulators and in the attic is my expansion tank and where I fill the system with water and I even have a Honeywell Heat Generator No. 1 (seen in pic).

Looking through the Ideal Fitter catalog section for No.7, this was an add on option $$ to pipe in domestic hot water so I can confirm at one point in my home’s history the original owner (lived here 54 years) used the boiler for both heating and domestic hot water. Owner 2 (lived here 60 years) would have probably been the one to make the jump over to a freestanding water heater (family of 7, five daughters 😃).

The thing I’m lost on is whether this would work since the system is all gravity and this would be in the basement at the same level as the boiler. I would love to rescue a nice Rococo rad (like the rest of the house has) and pipe it in here.

I value all the expertise here, and appreciate the thoughts, opinions, do’s, donts, and any your experiences with basement radiators, and etc. Mr. Holohan, if you happen to see this post would love to hear your thoughts/ a story around basement rads you might have.

Thank you all for your inputs! It’s ok if you choose to call me crazy for even thinking this. 😆

***The thermal pics were after the boiler had been off for two hours or so.

delcrossv · January 6

You need some vertical height so there can be a density gradient for circulation. Maybe a high wall mount or ceiling mount, but i doubt a floor mount rad would circulate without a pump. A tall wall mount would give a good gradient for circulation. (mimicking a tank)

Jamie Hall · January 6

As @delcrossv says, without a height differential you won't get much circulation — but what I would do is find (beg, borrow, steal) a nice watertight old radiator and a small pump — needn't be much — and pipe it up to just circulate from the boiler through the radiator. Put a thermostat on it to control the pump (if the pump is line voltage, which is likely, just get a cheap 120 volt thermostat from the BigBox — no relays or aquastats or anything fancy like that) and wire it up with an on/off switch as well. It will be easier if you have a way to thread pipe — but some big box stores will thread whatever you need for you.

Don't be tempted to do it in PEX. There will be times when the boiler water is hotter than PEX can take!

And then relax and enjoy you man cave.

Jamie Hall · January 6

I might add — that won't affect the rest of the gravity system at all, and you don't need any more expansion tank volume for it.

EBEBRATT-Ed · January 6

Yes you can. What you have sticking out of the boiler with those two pipes is a "Tank heater" which used to heat domestic hot water. Similar to a tankless heater. The tank heater used to heat a water tank off the boiler.

If you want to use gravity you will have to have your radiation above those two pipes and all piping must be above the two pipes. You will need an expansion tank and a fill valve at a minimum.

If you want to drop the pipe low you can install a circulator pump.

mattmia2 · January 6

https://forum.heatinghelp.com/discussion/comment/1832406#Comment_1832406

So those are just connections in to the boiler for a sidearm heater with the coil in the water heater, not a coil inside the boiler?

bburd · January 6

The coil is inside the boiler. It has much less heating capacity than a tankless coil because it's meant to heat a separate storage tank.

EBEBRATT-Ed · January 6

@mattmia2

The coil is in the boiler. Its similar to a tankless. The two pipes shown are the domestic water. You would hang a big HW storage tank close to the ceiling and connect the two pipes to the tank.

You needed enough height to make it work. The water in the storage tank would circulate through the tank heater by gravity or you could pump it if you had to.

mattmia2 · January 6

So as long as it is a relatively small load(which basements usually are) they can just connect a circualtor, relief valve, expansion tank, and prv and use that to heat a hot water loop in the basement.

Make sure it wasn't abandoned because it was leaking before you get too far.

PC7060 · January 6

Agree with @Jamie Hall you will need a pump if you use the domestic taps off the boiler.
Is there anyway you can tap into the main distribution lines of gravity system? If so the gravity flow generated by the high temp water (160-180f) moving through radiators on the upper levels will definitely pull water through a radiator at basement floor. I have two piped into my system that worked very well in gravity configuration.

In 2020, I converted to a low temp system using a modcon boiler with a small alpha2 circulator on low (8 GPM / 8 watts). The basement rads located 6’ below the trunks work just fine.

delcrossv · January 7

https://forum.heatinghelp.com/discussion/comment/1832451#Comment_1832451

IIRC the coil is in the tank. it's just a tap with a scoop inside the boiler. See the OP's boiler manual pics. The fitting looks specialty, like a diverter fitting. @Jamie Hall 's way is simplest: little pump, no expansion tank required because it's common to the boiler proper.

bburd · January 7

I had an Arco Severn boiler from 1947 with a tank heater like that threaded into the rear section. When I disconnected it, I found three tubes connecting the upper and lower tappings. Domestic water circulated through the tubes, which were surrounded by boiler water.

EBEBRATT-Ed · January 7

@delcrossv

There is no scoop in the boiler. The tank heater is just like a tankless heater coil. They used to have a plain steel hot water storage tank that was removed. The water circulated by gravaty between the tank heater in the boiler and the storage tank. Cold domestic water goes in the tank heater and hot water comes out.

EBEBRATT-Ed · January 7

Similar to what I attached below. You could install one in a boiler (if you had the tapping) and pump domestic water through it to a storage tank or install it in a storage tank and pump boiler water through it (like an indirect)

In this case the OP wants to repurpose one to use to heat a basement heating loop. They are just called tank heater because thats what they were used for. There just a heat exchanger

tacopdftmp-250107040453.pdf

Adding a Radiator on a Gravity System in the Basement

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