Do high output baseboards make a big difference?

MSmithHH

Hey folks,

My house was built in the late 80's. I've got a ton of large first floor windows throughout, most of which have been replaced, and my family room is 2 stories, again with lots windows. I'm in the North East and in the cold months, the house is cold. The heat might be set to 70, but it's often only made it up to 64 at best on the cold days (even as low as 59 on the coldest days). I've got a new efficiency boiler, which is sized correctly and plenty of baseboards. So, we're faced with a decision. Change the fireplace in the family room to a wood stove insert (which I think should have a significant improvement) or replace the baseboards with high output baseboards. I don't have a great spot to put a new wall unit in, so that's not really a good option and likewise for adding mini-splits.

The least disruptive solution and potentially cheapest, would be high output baseboards, but would it actually make that big of a difference? Or would it just be that I can hit 66 instead of of 64, but still not approaching that desired 70? If so, I think I'm best off with the insert. Thoughts?

Thanks

Zman

A couple quick things to check:
Is the boiler temp output set as high as possible to get the max output to the heaters? 190 degrees?
Are you getting adequate flows to the radiators? What is the temp difference between supply and return pipes?

If you need to make upgrades, it would be best to do a room-by-room heat loss calc and then design the heaters to meet that load rather than guessing.

MSmithHH

Hmmm....Thanks. Will check those. Honestly don't know the answers. We did heat loss calcs when the system was installed and picked the boiler based on that. I've got a great company that installed it and does service it yearly so I'm pretty sure it's tuned, but will double check. Would be nice if it was simply a flow issue or a setting issue.

If we assumed though that it's tuned correctly, do high output baseboards make significant impact or relatively minor?

EdTheHeaterMan

You can check the water temperature to see if you can get more heat from the existing emitters. You can also check the specifications of the existing radiation, Many of them are available on the web. For example Haydon is a popular brand that I used to install. Here is the spec sheet for the most popular model 750



You can see that the flow rate and water temperature can change the output.

Compared to the high output model 1000, there are several pipe sizes available along with the larger dimensions. The larger dimensions allow for more air flow for convection air currents to move more heat into the space. You can get up to 33% more capacity as seen in this spec sheet.



690 BTU to over 1000 btu per foot is actually greater than 1/3 more heat. Is that significant? Just make sure there is 3 more inches available below the glass to replace the emitters.

You may want to make that room a separate zone with its own thermostat

Jon_blaney

It the company is so great, why are you cold.

bburd

There is good advice above. One important point has not been mentioned:  If a heat loss calculation shows that the existing radiation is undersized, does your boiler have enough capacity to supply the additional heat that high output baseboard can emit?

The math is simple: Multiply the number of feet of finned element in the existing baseboards to remain by the Btuh output at the average supply water temperature you are using (Usually about 600 Btu/foot for standard baseboard); then do the same for the high output baseboard.  Compare the total to the net IBR output of your boiler.

Jamie Hall

In answer to the basic question -- they make a difference ONLY if the boiler is able to feed them enough heat in the first place.

Now if the boiler was correctly figured and sized in the first place, then switching to high output baseboards would let you get more BTUh per foot of baseboard at the same water temperatures as the regular ones.

How do you know if the problem is inadequate boiler output or inadequate baseboard? Several ways to approach this. First, and simplest, is to simply note what the boiler output and return temperatures are. Is that output temperature as high as it can be? It can go up to 180 usually. If it isn't up to 180, why not? Crank it up and see if you are comfortable. Second, also simple to note, is does the boiler run continuously on a call for heat, or does it come up to whatever temperature it is set for and shut off, while the circulation continues to run? In that case, there are three possibilities: either there isn't enough flow from the boiler to the system to transfer the heat which the boiler can produce, starving the system, or there isn't enough flow in the system to transfer the heat to the baseboards (the return temperature will be low in this case), or there isn't enough baseboard to absorb the heat from the boiler at the water temperature being used.

The very first possibility up there is the most likely: the boiler isn't set to produce hot enough water. Fortunately, that should be easy to fix, and with a high efficiency boiler is very likely, as to get the high efficiency from the boiler the installer will have set it to run at as low a temperature as he or she thought would do the job -- and it is pretty simple to change the settings on the controller (usually...)

I can comment further if you can find out what the boiler output temperature is set for, what it actually reaches, what the return temperature is, and if the boiler runs continuously.

Changing out the baseboards for high efficiency will only be a help if the boiler itself has enough power. If the boiler does have enough power, you can let it run at a lower temperature with high output baseboards -- but I doubt very much that the gains in efficiency in the boiler will offset the cost of the changing the baseboards.

HVACNUT

My first question is, did you have this problem with the old boiler?
What's the make and model of the boiler?
Do you know the approximate square footage of the heated space?
You mentioned a "new efficiency boiler". Is there outdoor reset? It could be as simple as an adjustment to the curve.

EBEBRATT-Ed

@MSmithHH

Something is amiss. You have a good company, plenty of baseboard and the right size boiler................But you are cold.

Get them back and have them find the problem

Either your water temp on the boiler is too low, the boiler isn't large enough (doubtful) or you don't have enough radiation.

This is assuming the system is pped right and has the correct circulator

MSmithHH

Ok, got some answers...I think.

So since we had an indirect water tank attached to the boiler for hot water, while a hot shower was going, the boiler was calling for heat (screen was red). At that time, the boiler said:
Target: 190
Supply: 149
Return: 128
Outdoor: 43
Input: 1 2
Pumps: 1

But when a shower wasn't going and the house 58 degrees while set to 68, the boiler was not calling for heat (screen was blue, however zone lights were on so it was still sending). At that time the boiler said:
Target: 168
Supply: 167
Return: 161
Outdoor: 17
Input: 2
Pumps: 2 BC

To be honest...I don't know how to interpret those numbers. Perhaps someone here can give me some insight? Should I be trying to raise the target temp so that it's always 190?

As to the baseboards, there's no brand/model markings I can find on them. The inside fins are warm to the touch. Perhaps interestingly though, the upstairs ones at the same time which are on a different zone when the temp was 65 but set to 68 were cold to the touch.

For the previous boiler...not sure...replaced it when we moved in. But other homes in the neighborhood built at the same time by same contractor have had similar complaints and they added gas fireplace inserts or mini-splits with success.

Any thoughts on all this? Thanks!!!!

EBEBRATT-Ed

Sounds like you need some combination of:

Higher water temp
more baseboard
larger baseboard

You answered you own question

The house is 58 degrees, the stat is set for 68 (your 10 degrees off set point)

Your boiler is back down to low fire and you need heat!!

How do I know this?

Your boiler target temp (the temp the boiler is being told to get to) is168. Your boiler is at 167 it's doing its job.

Your supply temp of 167 and return of 161 (same temp in and out of boiler basically) means the burner is barely firing like a pot on the stove simmering.

This first thing to do is the simple thing. Raise the target to at least 190. But you may not be able to get their. Some mod cons are only set up to run about 175 max (its the Europeon way)

The real question is did the baseboard heat the house with the old boiler & now it won't with the new boiler?

Doesn't sound to me that your service company is on the ball

MSmithHH

I took another reading about 90 minutes after the past as a point of comparison. House is currently 61 degrees and set to 68. New reading is:

Target: 166
Supply: 162
Return: 155
Outdoor: 20
Input: 2
Pumps: 2 BC

So the target temp dropped by 2 degrees for some reason. But not sure what that actually means, so....

Thanks

MSmithHH

@EBEBRATT-Ed

There's definitely a lot of baseboard. It covers the length of most exterior walls of the house and it's a 4k sq ft house, so there's a lot of linear footage. Funny that the target dropped on that last reading. Maybe because outdoor temp jumped slightly? The target though seems to be self-regulating, so if I adjust the target temp won't that mess with its self regulation?

Ok, and I think I see what you're saying in regards to the baseboards. Supply and return only have 7 degree difference, and sounds like I should be seeing a higher difference (like maybe 15?), meaning my baseboards either aren't releasing enough heat, or there's not enough of them.

In regards to the old boiler, I was only here for 1 season with it, and not sure if that was a warmer season or not. It was cold, but not sure it was this cold.

Thanks!

fentonc

I believe your boiler has an 'outdoor reset' control, which sets the 'target' temperature based on the current outdoor temperature (the higher the outdoor temperature, the lower the target temperature, since it should be easier to heat the house as it gets warmer outside). You can see that the outdoor temp was 17 and the corresponding target was 168, and then the outdoor increased to 20 and the target correspondingly dropped to 166.

It sounds like everything is 'working' properly, in the sense that your thermostats are continuously calling for heat, and the boiler is easily reaching the target temperature and maintaining it there, it's just that the combination of target temperatures and baseboard you have isn't actually enough to keep up with the heat loss for your house. Adding more baseboard (or higher output baseboard) would help increase the heat output, but you should just be able to change the 'outdoor reset curve' (basically the relationship between outdoor temperature and target temperature that the boiler uses) for your boiler so that it uses a higher target temperature for a given outdoor temperature, thus increasing the heat output of your existing baseboards.

MSmithHH

I see. That makes sense. Thanks. It's a Weil Mclaine WM97+100CT. I'll break out the manual and see how to do that and give that a shot.

ratio

MSmithHH said:

Ok, and I think I see what you're saying in regards to the baseboards. Supply and return only have 7 degree difference, and sounds like I should be seeing a higher difference (like maybe 15?), meaning my baseboards either aren't releasing enough heat, or there's not enough of them.

This is where I'd start looking at. First, anything blocking the airflow around the baseboard? Next, are the fins clean of e.g. pet hair etc.? After that, the heat-emitting part of the baseboards is the finned part of the pipe. It's not going to be identical to the length of the baseboard itself, measure it while you're cleaning the fins. It's still possible that you don't have enough emitter length to get the necessary heat output for the water temp you're sending to the BB.

fentonc

It looks like the relevant settings are on page 78: https://weil-mclain.com/sites/default/files/field-file/wm97-ct-manual_1.pdf

EBEBRATT-Ed

I looked at the boiler manual quickly. The manual reset high limit is 200F. They say a target temp of 180 is what they recommend for baseboard.

It also say target non adjustable if the boiler is a COMBI

fentonc

Just as a test, to adjust the outdoor reset curve, I think you would want to increase the value of the "MIN OUTDOOR" setting:

MIN OUTDOOR means the outdoor temperature at which the target
temperature reaches its maximum value (MAX SUPPLY).

Basically tell the boiler to run the water temp up to MAX_SUPPLY when the outdoor temperature is warmer - if you set it to 50F or something, I think it would effectively disable the outdoor reset curve since every time it was below 50F outside it would just use the max temperature. You mainly want to see if there is an achievable target temperature that *does* let you meet the thermostat value when its cold outside (without needing to add more baseboard).

MSmithHH

EBEBRATT-Ed said:

It also say target non adjustable if the boiler is a COMBI

I have a separate hot water tank (which looks like a standard water heater) that the boiler is responsible for heating. Think they called it an indirect tank. The definition of a COMBI, sounds like what I have, but others on the interweb seem to be calling my setup different than a COMBI.

fentonc said:

Just as a test, to adjust the outdoor reset curve, I think you would want to increase the value of the "MIN OUTDOOR" setting.

Will do! Will report back. Thanks

Jon_blaney

There is a comment in here somewhere about "cold" baseboard. Why?

Jon_blaney

Are the thermostats set for a given temperature or do you change them up and down or use a set-back?

sjchalela640

Maybe isolate your indirect when you have a couple hours and see if your house gets to temp. Could have a possible issue with a fixture 

MSmithHH

The thermostats are on a fixed schedule.

Not sure why some baseboards are often cold. Even the ones actively heating aren't what I'd call hot, but I'm not sure how hot they should be so maybe it's normal. I can touch them no problem though

The indirect is only heating when the screen is red on the boiler and mostly only happens after a shower.

Jon_blaney

Still not clear to me. Set to one temperature all the time or does is change over the day?

MSmithHH

Apologies. By fixed schedule I meant that at 7AM the temp is set to 68 degrees on the first floor. At 2PM it raises to 70 degrees. I also have the preheat setting so it attempts to bring it up to temp earlier so that it's ready. At 8:45PM it's set to 60 degrees.

Jon_blaney

I believe this schedule is much of your problem. The thermostats are yes/no switches, circulate or not. The water temperature is set by the outdoor reset. The system is designed to replace expected heat loss and maintain a steady temperature. If you lower the temperature, the system will only provide enough BTUs to maintain that temperature. There is not a function to recover all the lost BTUs from the setback. The temperature should be set and left alone. You should have constantly circulating water at a temperature set to meet heat loss. This is unlike an old fashion system with large excess capacity where there are always BTUs available and circulation is intermittent. The fireplace gas log others use, proved the makeup BTUs.

Check that you are getting circulation in all zones, set the thermostat to fixed setting and leave them alone. Get some space heaters to get the inside temperature up to set point.

Adjust the thermostats in each zone consistent with use, no up or down. Make sure the reset curve is matching your conditions.

Jamie Hall

As @Jon_blaney said, the combination of a setback -- any setback -- and outdoor reset is just wrong, no nicer way to put it. The whole idea of outdoor reset is to set the boiler so that it matches the structure heat loss -- just barely -- and so runs all the time. If you now raise the interior house temperature without changing the reset curve, the boiler is never going to make it -- it was running all the time anyway.

Ditch either the outdoor reset or the setback.

Jon_blaney

A 10 degree setback is to big regardless.

EdTheHeaterMan

MSmithHH said:

Apologies. By fixed schedule I meant that at 7AM the temp is set to 68 degrees on the first floor. At 2PM it raises to 70 degrees. I also have the preheat setting so it attempts to bring it up to temp earlier so that it's ready. At 8:45PM it's set to 60 degrees.

Unless your thermostats are communicating with the outdoor reset (ODR) control (with the WM Boiler they are not) you should not use setback. By communicating I mean that the the thermostat sends a signal to the ODR that it is in recovery mode and will automatically raise the boiler target temperature during the recovery period. Your thermostats are most likely just ON/OFF temperature switches with no communication capability.

Ditch the setback or disable the ODR. I would opt for the ODR and disable the setback. I believe the continuous operation modulation saves more than setback.

MSmithHH

Wow...very enlightening. Thank you! Two follow up q's:

1) What's interesting (to me at least) is that from the time it turned on at 7AM to the time it turned off at 8:45 PM, it never made it to temp. It was still up to 10 degrees colder even at 8PM. Is that expected?

2) Should I do this for rooms that I don't have an issue with? Like my master bedroom which is on it's own zone, I have it set to 60 at 8AM and then 68 at 8 PM. This room gets up to temp and is not being heated all day. Seems to work fine. Is it better for the system though if I just set it to 68 degrees 24/7? Similarly for my attic, I'm not in there at all on the weekends and just use it as an office during the week. Should I still be heating it 68 degrees continuously?

Jamie Hall

With regard to 1). No, it's not expected, and it's not right. It's possible that higher output baseboards might be able to put out enough heat with lower temperature water to improve things, but to make up that much setback in an hour or so you need a lot of heat -- and you will need to raise the water temperature. For a daily setback, 10 degrees is, in my view, excessive and, as @EdTheHeaterMan said, you will probably do better with just the outdoor reset and no setback. However, if you do want the setbacks, kill the ODR and run the boiler temperature at whatever it takes to heat the spaces in a reasonable length of time.

Now if there are spaces which you don't use for several day (number 2 here), you may find it practical -- and it will save some fuel -- to turn them off or down if you will not be using them for a couple of days. Similarly for the master bedroom -- though I wouldn't go down to 60, since it has its own thermostat a setback may work. If you run up the water temperature (see 1), it will recover more quickly.

Jon_blaney

As my son would say, "pick one and go with it", then we can help you fine tune your system.

MSmithHH

Welp, a big THANK YOU to everyone here. First I removed the setback from the thermostats. Kept it like that for 48 hours. It helped a little, but only a few degrees...but still clearly a necessary step. Then we changed reset curve and have it hit 180 degrees at 30 degree outdoor temp. Also adjusted it's perceived outdoor temp because it was slightly off. Within hours there was a tremendous difference. For 2 days now, my whole house has been fully up to temp, which has never happened, and in every room. It feels hard to believe that my heating bill won't rise dramatically, but I'm accepting that I don't know what I don't know Anyways, not gonna need that fireplace insert, and doesn't appear that I need new baseboards either.

Thanks again everyone!

Jon_blaney

Thanks for letting us know how it worked out.

kevinhoffman

a fireplace insert may not be a bad idea for emergency heat ,power outages seem more frequent these days

CMadatMe

From the readings you posted you seem to have a proper Delta-T when making DHW but a very small (improper) Delta-T when in heating mode. In other words all that seems to be happening is that btu's are taking a train ride but not getting off at its stops. Sounds more to me that there is either a piping or pump issue. I'd assume the indirect is piped on the boiler side of the closely spaced tee's/low loss header? Do you have pics?