Are these two Hot Water Baseboards the same?

CoalBoilerGuy

I'm wondering if the "Sterling Heatrim Plus" and "Design Line Synergy" hot water baseboards are one and the same?

And if they are different, which is to be preferred?

motoguy128

Both companies are owned by Mestek. But comparing heat output per foot at the same temp and flow rate, they are slightly different, so I’d guess it’s not the same element or enclosure. They are within 10% output, so nearly equal. Synergy is 913@180F, 4GPM. Heatrim is 850 at the same conditions.

CoalBoilerGuy

I was going by their outer housing dimensions, which appear pretty much identical. You are probably correct in that they use different fin tube elements.

The reason I'm inquiring is because I recently switched to a NG fueled mod-con boiler and my 1964 era baseboards that appear similar to something like a modern Slimline 30 series are not giving me the Delta-T I need to push my boiler into condensing territory as frequently as I'd like. These two seem to have outputs that would improve my condensing situation, hopefully without breaking the bank. I have 4 zones, each with right close to 40 feet of HWB.

Does anyone have a price comparison between them? That would be my motivator if I decide to pull the trigger and get it done. I'm in N/E Ohio.

Jamie Hall

The other way to get the delta T is... reduce your flow rate. Don't have to change any elements. Don't have to hassle with that.

What do you have for flow control on your system?

Alan (California Radiant) Forbes

Have you tried reducing your heating curve? Maybe a supply water temperature (SWT) of 130F will still heat the rooms on a mild day and a 145F SWT will do the work on a cold day. With a 20° ΔT, your boiler will condense.

I just don't know if that will keep your rooms warm.

CoalBoilerGuy

Jamie Hall said:

The other way to get the delta T is... reduce your flow rate. Don't have to change any elements. Don't have to hassle with that.

What do you have for flow control on your system?

I have an Alpha circulator, and it is delivering as little as it can.

CoalBoilerGuy

Alan (California Radiant) Forbes said:

Have you tried reducing your heating curve? Maybe a supply water temperature (SWT) of 130F will still heat the rooms on a mild day and a 145F SWT will do the work on a cold day. With a 20° ΔT, your boiler will condense.

I just don't know if that will keep your rooms warm.

I'm going to need at least 165 degree on the supply side when it's really cold outside.

Jamie Hall

CoalBoilerGuy said:

Jamie Hall said:

The other way to get the delta T is... reduce your flow rate. Don't have to change any elements. Don't have to hassle with that.

What do you have for flow control on your system?

I have an Alpha circulator, and it is delivering as little as it can.

It's called a throttling valve. A valve (except a gate) doesn't have to be either on or off, you know.

But... changing the circulator to a nice delta T one is going to be a lot cheaper than changing all your baseboard. And save money while you're at it.

CoalBoilerGuy

Jamie Hall said:

CoalBoilerGuy said:

Jamie Hall said:

The other way to get the delta T is... reduce your flow rate. Don't have to change any elements. Don't have to hassle with that.

What do you have for flow control on your system?

I have an Alpha circulator, and it is delivering as little as it can.

It's called a throttling valve. A valve (except a gate) doesn't have to be either on or off, you know.

But... changing the circulator to a nice delta T one is going to be a lot cheaper than changing all your baseboard. And save money while you're at it.

It is a single circulator and 4 zone valves system. Are you suggesting throttling back the flow to all 4 zones?

hot_rod

Really no sense in throttling until you know what the rooms or zones require. The load calc would give you the required BTU per room, then match the fin tube output chart to that delivered amount of heat at the lowest SWT.

Delta T on any system will change as the load does. You may see a 20 or wider delta on cold start, it could narrow to 5 just before it shuts down.

Delta will be 0 when the zone is satisfied

Here is a snapshot of how heat transfer from a fin tube.

HVACNUT

What size is the boiler and what's its lowest firing rate?
Is outdoor reset being used?

CoalBoilerGuy

I've lived in this house for almost 21 years, and for the first 10 of them it was heated exclusively with a 13.5 KW (46,062 BTUH) resistance boiler, and for all but 2 days within those 10 years it did fine in keeping the house warm, wherein it struggled a bit on those 2 days only. Thus I have a very decent handle on my homes heating demand. What I will need in order to condense most often will be baseboards that deliver at 145 degrees of supply the same output as do my current baseboards at 165 degrees of supply. The resistance boiler maintained water at 165 degrees on the supply side. Failing only to do so on the aforementioned 2 days in 10 years.

hot_rod

You are on the right path to lower SWT to leverage that condensing boiler. Remember 80% or more of the heating season you are below design conditions, so setting up the outdoor reset will helpmkeep the boiler condensing as much as possible.

How many feet of baseboard don you have that the 46,000 boiler was feeding? That will get you some ballpark numbers to see how low SWT you could run.

CoalBoilerGuy

There are three zones for the house proper, with 38 Ft. of HWB for the combined Living room, Dining room, and Kitchen zone, 43 feet of HWB for the 4x bedrooms zone, and 40 feet of HWB for the 'finished' walk out basement/family room zone (which sits below the Living/Dining/Kitchen zone). There are then 26 feet of HWB for the garage zone, whereby the garage sits directly below the entire bedrooms zone, and is T-Stat regulated at only 47 degrees in the winter.

The current HWB's are all of the "conventional" ballpark 550-580 BTUH for 180 degree supply water type (with this including the 1.15X gross/net factor). Call it ballpark 450-480 BTUH for 165 degree water (with this including the 1.15X gross/net factor). Copper piping throughout the 1964 built house.

CoalBoilerGuy

HVACNUT said:

What size is the boiler and what's its lowest firing rate?

Is outdoor reset being used?

The current "low mass" NG boiler (~1.1 gallon capacity as I recall) is 80,000 BTUH on the input side, with 14,000 BTUH input at the lowest turn down. AFUE is 87% when not condensing, and "up to" 95% when condensing. Outdoor reset is activated and in use.

I have a 30 gallon buffer tank on the system as well.

Jamie Hall

You do have problems, don't you? For one thing, your boiler is almost twice as big as you found years ago it needed to be. That probably can't be helped, but... it's not helping.

But at least you have a buffer tank. That's something.

There will be very few days when you need 165 degree feed water to the radiation. What is needed, then is to control the buffer tank temperature -- and thus the boiler temperature -- with outdoor reset. If you don't have that, you will not be operating as well as you could be. Throttling all four zones will increase your delta T, true, but unless you have outdoor reset and use it, your whole system assumes that 165 feed temp -- and even with the higher delta T you won't get the condensing you'd like to have. Does your boiler have provision for outdoor reset? It should...

CoalBoilerGuy

Jamie Hall said:

You do have problems, don't you? For one thing, your boiler is almost twice as big as you found years ago it needed to be. That probably can't be helped, but... it's not helping.

But at least you have a buffer tank. That's something.

There will be very few days when you need 165 degree feed water to the radiation. What is needed, then is to control the buffer tank temperature -- and thus the boiler temperature -- with outdoor reset. If you don't have that, you will not be operating as well as you could be. Throttling all four zones will increase your delta T, true, but unless you have outdoor reset and use it, your whole system assumes that 165 feed temp -- and even with the higher delta T you won't get the condensing you'd like to have. Does your boiler have provision for outdoor reset? It should...

My boiler is running off of outdoor reset. It is condensing now, but I would like this to continue deeper into next winter.

I believe the outdoor reset is modulating the boilers supply temperature, as there is only the outdoor reset sitting outside on the north wall, and the boiler, and there is no aquastat on the buffer tank.

The boiler is running at low temperatures and it has its own circulator, so there are actually two circulators on the system, the boilers internal circulator which loops the boiler through the buffer tank, and the Alpha which feeds the zones off of the buffer tank.

When a zone valve opens on a T-Stat call both circulators start up, and the flame comes on in the boiler. It saw first fire on April 1st.

dopey27177

I think if you control the circulating pumps with the outdoor reset t stat in the house to control the boiler operation with the aquastat set at 180 for boiler temp.you will do a little better than what is recommended.

The delta T is the measure of the BTU drop at the outlet of the convector or zone. For most instances this irrelevant data.

Your burner or heating element always chases the desired boiler water effluent. The controls do not care what the delta t is. On cold days the delta t is wide, on warm days there might not a measurable delta t.

Your heating efficiency is dependent on the on off of the circulating pumps response to the desired indoor temp.

Jake

CoalBoilerGuy

Are you suggesting to move the outdoor reset to the aquastat tapping (sealed probe well) on the buffer tank somehow?

Jamie Hall

Well, actually, no. The efficiency of a mod/con boiler is determined -- within the range of non-condensing to full condensing -- solely by the temperature of the boiler. If you set the aquastat at 180, you might as well get a nice cast iron standard boiler.

Use the outdoor reset to control the boiler target temperature. To add to the efficiency, use a delta T control on the pump.

Sorry.

CoalBoilerGuy

Earlier I mentioned that this is a single circulator system. That is incorrect, as the mod/con boiler has its own internal circulator which also comes on at a T-Stat heat call, and serves the purpose of looping the boiler through the buffer tank and back to the boiler.

My main problem in ascertaining Delta-T is potentially due to poor temperature monitoring instrumentation. I have remote barbecue grill temperature sensor probes taped to the surfaces of both the supply and return lines (post the buffer tank) garnering surface temperatures (which I presume are likely to be some factor below the actual internal 1-1/4" copper pipe temps). Presently, with two of my four zones calling for heat, and thereby two zone valves open, and both circulators running, I'm reading surface temperatures of 129 degrees F. on the supply side and 122 degrees F. on the return side via the two probes of the barbecue grill thermometer. The boiler itself is being maintained at a steady 140 degrees F. as seen on its digital display, and it is presently 46 degrees F. outside.