Complete Revamp of Heating System, Removing Radiators

Old 11-28-16, 11:38 AM
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Complete Revamp of Heating System, Removing Radiators

I have a hot water boiler, maybe 8 years old. It has NO ZONES in a 1200 sf house. I have five radiators and then "some pipe" which I assume was supposed to work as a radiator. I'll try to explain that ... in a now "closed in porch" there are four runs of 3" pipe down the cold wall. It does not provide sufficient heat to that room.

OK, I want to improve on this. I love the radiators but they take up space and make remodeling the house difficult. As an example, in the kitchen how can I put cabinets down a wall that has a very large radiator.

So, I want to zone the new system and have in my mind to replace the radiators with baseboard units ... still hot water. In the kitchen my thought is to put them into the "toe kick" of the cabinets. I am building the cabinets myself and will provide the extra space in the toe kick.

I want to get this done in the spring when I can shut the system down ... or, is this possible to do during the heating season? I think I can cut into the existing "feed line" to the radiators, and use PEX to feed a manifold that has the proper switches on it to activate the individual zones, and run PEX from there out to each baseboard. Seems 1" PEX is right to use.

Overall, first question ... am I crazy to try this?
Old 11-28-16, 01:06 PM
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Completely crazy or just a little crazy?

For most DIYers, I think this would be a "stretch" project. Not because of the plumbing or carpentry skills required, but because of the heating system design knowledge required to get enough heat in the right places, while operating the boiler safely and efficiently, especially when converting to a zoned system.

You can get in the ballpark by assuming you need the same BTUs from convectors that you have in radiators, and if you go with zones that gives you some leeway because each zone will have it's own thermostat.

Good luck with your project!

Last edited by CarbideTipped; 11-28-16 at 03:00 PM.
Old 11-28-16, 01:51 PM
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As the previous poster alluded to, there is a significant design component to hot water heating. For example, 1 " pex has a certain maximum flow rate, which in part determines the BTU's that will be pushed through. 1 " pex is likely larger than what you need, but again. You need to design. You almost certainly only need 1/2 " pex from a manifold to each emitter. Piping to a manifold is likely 3/4 ", as you have a 1,200 sq. ft. home.

You can get a rough idea of your BTU output for each room by gathering the radiator EDR (google how to do it). But it also depends on flow rate, your Delta-T.

I personally would keep the radiators - you can always move them, since you would be using pex to pipe, however using pex with old radiators is work, as opposed to piping all new to new baseboard emitters. Using pex with a manifold is a common solution for both baseboards and radiators.

I've never heard of putting baseboard radiators under cabinets, but have heard of hot water coils with fans designed to go under cabinets.
Old 11-28-16, 05:14 PM
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Depending on several variables zoning a 1200 square foot house might be a mistake. My house is 1500 square feet, all on one level, and I would NOT want it zoned. The possible downside to zoning is you end up with what are called "micro zones" that cause the boiler to short cycle unless you have a large amount of water in the system.

Using baseboard convectors under cabinets would not be a good idea in my opinion. Baseboard convectors work by having the cooler room air enter at the bottom and then the air rises through the fins being expelled out the top louver. Anything that impedes this air flow will be detrimental. Fan forced heaters are often used under cabinets but the fan can be noisy and is also one more thing requiring maintenance.

Regular PEX piping cannot be used as it allows oxygen to diffuse through the tubing walls and that will cause corrosion of any steel parts of the system. You need to use an oxygen barrier PEX tubing that is considerably more expensive and somewhat less flexible.

I personally detest cast iron radiators. I suspect that your porch with the pipe radiator is woefully UNDER radiated so baseboard convectors would probably be a big help. Your boiler is likely oversized but in some circumstances that is not always bad.
Old 11-29-16, 06:50 AM
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Furd: The possible downside to zoning is you end up with what are called "micro zones" that cause the boiler to short cycle unless you have a large amount of water in the system.
A major advantage of of hydronic systems is that one hot water boiler supplies a number of zones. Burner only fires when water temp drops below setting. The burner is not controlled by zone thermostats, but by water temperature/btu loss.

Furd's “micro zones” is a new one and linking it to short cycling leads to fuzzy thinking. The boiler is responding to building heat loss, not whether it is from a small or big zone. Water capacity is not a significant issue in systems that typically run less than 75% of time.

Oil burner short cycling, often described as more than 3 or 4 cycles per hour or less than 4 minute cycle, is carried to excess by many leading to inefficient systems. A 60,000 btu/hour boiler firing for 4 minutes is less efficient than when run twice for 2 minutes. Any difference in MTBF is negligible. In air condition systems, short cycling can be a major issue.
Old 12-07-16, 05:50 AM
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Anything that impedes this air flow will be detrimental.
Never thought of that!

I would prefer in-floor radiant heat in the with a tile floor ... problem is the floor is springy ... the tiles would crack.

I was going to "sister" in joists to tighten it up, but it is a huge project in the basement. As it is right now I can not get joists up there to sister them, too much piping and wiring in the way ... of course if removing all this piping and going with PEX to feed the heat out as well as return to the boiler, I could have that much out of the way to sister the joists ... I guess.

How about putting blocking between the joists every few feet? Same is is done anyway in most floors ... except not in this one. Would that be effective enough to tighten the floor up from being springy and not crack a tile floor?

Did I mention this house was built in 1925?

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