Recessed (In Wall) Convector Box Replacement/Upgrade ???

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Old 10-07-11, 04:41 AM
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Recessed (In Wall) Convector Box Replacement/Upgrade ???

Hey Guys,

I have a 50s cape with recessed hydronic connvectors in wall. Lats year I cleaned the convector fins up very well for an increase in heat output.

I'm still strugling with heat outut.

I think the biggest problem is the diameter of the feed lines going from the central loop to the perimeter of the house. It is a monoflow system, and the feeders are old narrow gauge pipe. The main loop and monoflow T's are newer.

I am about to start a basement remodel, which will give me complete access to the piping. I'm wondering if replacing the old piping with new piping (larger diameter) and possibly replacing the actual convectors for something non 1950s era would help with the overall heat output of the system?

Are newer convectors available? Are they more eficient? Are there fan boosted convectors? Would increasing the flow to the convectors help with heat output?

I still do not have any insulation board behind the convectors, which is another option for upgrade.

I'm open for suggestions, as I would an increase in heat efficiency.

All help is greatly appreciated.

Many Thanks,

Bryan
 
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Old 10-07-11, 03:25 PM
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I doubt the piping is too small if you are on a monoflo. What is the diameter of the monoflo loop? What is your heatloss and what is the maximum oupt in btu's of your convectors?

Moving the water faster through the pipes may help, but someone else more knowledgeable will have to comment on that. Adding more convectors and insulation will help.
 
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Old 10-07-11, 03:50 PM
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There's usually not a heckuva lot of difference between the 1 GPM and the 4 GPM ratings on the baseboards or convectors.

Even 1/2" pipe can support 15K BTU of heat load, and I doubt you have any convector cabinets that big! In other words, if the piping from the monoflo to each convector is 1/2" you will be fine.

You can get a general idea whether or not there is adequate flow through a convector by simply doing the 'ouch test' on the supply to and the return from the convector. Grab a hold of the supply... get an idea of how hot it is. Now do the same on the return. Is the return still hot? lukewarm? cold? If it's 15 or so cooler on the return, your flow is fine.

3/4" pipe can support a heat load of approximately 40K BTU, and 1" can support appx 70-80K BTU.

What size is the main loop?

Have you done a room by room heat loss analysis of the home?

Compare that to the output of your convectors.

There are of course new convectors available, and there are also things like 'panel radiators' too... but the first thing you need to know is whether or not you have enough HEAT EMITTER capacity to counter the HEAT LOSS. Without knowing how many BTU you need to heat a space, you can't determine the size of the emitters you need.

And still... the cheapest fuel that you can buy is INSULATION and CAULK !
 
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Old 10-07-11, 05:53 PM
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Hmm. I'm wondering if there could be air trapped in the convectors. Given that it is a mono flo system, maybe it wasn't properly bled.
 
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Old 10-07-11, 06:21 PM
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Very possible! The ouch test might help to determine that.

Bryan, are there air vents inside the convector cabinets?
 
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Old 10-11-11, 08:34 AM
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Hey Guys,

Sorry for the delay in response, as I was traveling this weekend.

I will look into the pipe diameters, but I'd say the main loop is probably 3/4 with maybe 1/2 branch lines to the convectors.

I'm not sure about the BTU ratings for the convectors. They are original late 40s vintage, most about 24-30 inches long. There were at one time vents in the cabinet, as indicated by the pull-chain hole, but they have since been removed.

The pipes leading to and away from the convectors are hot. I have not measured the temp differential from input to output, but I can not hold either pipe for long before the pain sets in....

My main complain is that it seems the homes heat does not cut it. It takes forever to bring the house up to temp, and it does not stay there long. On the coldes days of winter, it can barely keep up without constant running of the burner.

Would you guys want me to report back with the exact pipe dimensions?

What else can I do to help diagnose the issues???

Thanks again,

Bryan
 
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Old 10-11-11, 08:37 AM
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Here is a link to an old thread with pics of the convectors. They are all approximatley the same size...

Link
 
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Old 10-11-11, 09:28 AM
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When designed properly, it is supposed to run continuous on the coldest day of the year. When you say it barely keeps up, does the temperature of the house fall? How much does wind affect your situation? On these days, about what is the outside temperature and what temp is the thermostat set to?

It sounds like you set the thermostat back at night or during the day when you are gone. If so, ho far back to you set it? With a boiler properly sized, it will take a long time to bring the inside temperature up from a set back. I actually abandoned my set backs when I had my new boiler installed. I found the house to fell far more comfortable when I did.

It may be the case that you could use a touch more radiation, but we won't be able to know if we can't figure out the ouput of your convectors. I don't have anything about you style of convector that would provide that info. Maybe someone else can get things pointed oin the right direction.
 
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Old 10-11-11, 09:39 AM
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I usually set the temp at 68-69F during hours when we are home, and then the thermo sets back to 64 when we are away and at night. I would think the rate of temp change is about 1-2F/hour during the cold winter days.

On the coldest days of winter ~0F, I keep the heat set at 68, and the system runs pretty much contunuously.

Would it be best to keep the system at 68 constantly, and defeat the automatic thermostat?

I'm not sure about how wind affects the condition, as I have never been conscious of it...??? Id say I would check, but that is still a few months away.

Thoughts?

BK
 
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Old 10-11-11, 11:13 AM
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I asked about the wind because of my experience with my home. My second floor is poorly insulated and on windy days, the warm air is blown right out of the house.

I would say things sound be sized just about on target. Do you do a set back when you experience the coldest temps? If not, I would try it out for a week or two to see how things go. You may be happier with it like that. If 68 is too warm for you to sleep with, maybe we can figure out a way to cool off just your bedroom.
 
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Old 10-11-11, 11:29 AM
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I'm not sure if how accurate this will be, but I found some BTU info for similar cabinets that you have. There are tables for BTU output in this link. I believe you take the number in that chart for the corresponding style and size and multiply it by 1,000. So if you figure out the ouput of your convectors, and do a heat loss calculation on your home, you should get some idea of what is going on with your system.

What is your high limit set to on the boiler? Is it 180?
 
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Old 10-11-11, 04:41 PM
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Droo, I think you forgot to post the link... Bryan, do take a look and see what the high limit is set on your boiler.

If the pipes in and out are both hot, then you certainly have flow in the convectors, but there still could be air trapped in them which would decrease the BTU output.

There were at one time vents in the cabinet, as indicated by the pull-chain hole, but they have since been removed.
That chain would have been for a DAMPER to control the room air flow through the cabinet. What I meant was an AIR BLEEDER valve to purge air from the convectors.



See that thing on the left side sticking up? That's an AIR VENT. The top of it may be square and require a 'clock key' to open and close, or there may be a screwdriver slot.

Before you try to open it, please take a close up (use the macro function on your camera) because I want to make sure it's not one of those 'automatic' types that I despise.

But what you would do with that if it's the manual type is open it and vent any air that has collected in the unit. Hopefully they all have them installed.

Would you guys want me to report back with the exact pipe dimensions?
Probably not necessary, I can see from the pics that it does appear to be 1/2" to each cabinet, and that is fine. If the main loop is 3/4" it may be a bit on the smallish side, but it depends on how many convectors and how many BTUs are on that circuit.
 
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Old 10-11-11, 05:14 PM
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Old 10-11-11, 05:28 PM
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Hey Guys,

The convectors all have bleeders, and they are bled each pre-winter to insure no air is trapped in the lines. I open each screw-driver slot until all the air is out and I see water running from the output. You guys helped me out with this last year when I was having some air issues. Last year there was ample air, and this year ther is very little and all the convestors seem to be passing water...

The high limit is currently set at 180F.
 
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Old 10-11-11, 05:30 PM
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Yes, I would think those ratings would be pretty much the same. Thanks Droo!
 
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Old 10-12-11, 08:29 AM
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Originally Posted by bryankloos View Post
The convectors all have bleeders, and they are bled each pre-winter to insure no air is trapped in the lines.
If your system is pressurized all summer, no air should get into the system. Bleeding air should only be necessary if you open the system for maintenance or if your air removal device(s) aren't functioning.
 
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Old 10-12-11, 08:32 AM
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This is a good thing, given I have virtually no air in my system this year... It was opened last year, hence the need for bleeding...
 
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Old 10-12-11, 07:20 PM
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Address the heat loss in the whole house. That is thing 1. Get a real energy audit from a real building diagnostics company. Blower door test with thermal IR. It is the best money you will spend.

After the test, get a good insulation/sealing company to do the whole house, or as much as you can afford, following the needs identified in the audit. In MA, you can get a bunch of incentives, rebates, tax credits, etc. Start here:

DSIRE: Incentives in MA : Massachusetts Homeowner Incentives for Energy Efficiency

After that, if the heat is still not adequate, then you need to think about other options. But for the moment, it appears the system is bled and functioning, so address the building before throwing money at the boiler, convectors, and controls. Think of insulation and air sealing as fuel you only pay for once, and it works essentially forever to increase efficiency and comfort.
 
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