Help with System Upgrade

Lynnwill

If anyone gets time please help me choose a proper system upgrade.

My system is a converted gravity type. Typical dual 2" mains and 1" to 23 cast iron radiators, 1055 total EDR. My heat calc says approximately 100MBH at 5/74. The boiler is a 9 yr old Burnham Series 2, rated 84%AFUE, 164/136MBH in/out. There is a small radiant zone and an indirect Alliance AL53L indirect water heater. There are a Tekmar 260 controller and a TACO 2 zone relay. My system is on/off. The large mass of water entering the boiler with results in 90-120 degree boiler temperatures. Obviously no good for a non-condensing cast iron boiler. The heating is uneven with warmth, a cool down then back to eventual warmth - kind of like an air system with longer cycles. I have changed the DWH circulator to a Grundos Alpha and the main zone circulator to a TACO VT2218. My goal with repiping is constant circulation of the main zone with indoor temperature feedback. Local professionals do not seem to agree on how to implement this. One contractor would do P/S and keep the existing controller with limited repiping (highest bid?) - the other would do away with existing P/S and add controls/mixing.

I have attached an existing, proposal #1 and proposal #2 drawings. Both proposed drawings include mixing, outdoor reset, boiler protection and a Tekmar 403 controller. Mixing would be with an actuator. One plan is P/S on the main zone and one is direct. I would set the boiler minimum at 140 degrees and full reset at the mix temperature. With indoor temperature feedback i should have constant circulation on the main heating zone. With only only one main zone do I even need P/S?

I understand I am asking a lot. Any comments are appreciated. Thanks if you have the time (or interest).

Paul48

Without looking at everything, you need to know how to properly set up the thermostatic mixing valve.
http://www.caleffi.com/sites/default/files/file/38476.pdf

Snowmelt

Id be installing a bypass for the low temp application. i would also install a primery / secounday with a whirling seperator.

SWEI

Lynnwill said:

My system is a converted gravity type. Typical dual 2" mains and 1" to 23 cast iron radiators, 1055 total EDR. My heat calc says approximately 100MBH at 5/74.

At 95 BTU's per square foot, your radiation will only need 140°F water on a design day. The other 97.5% of the time, it can use even cooler water. This practically screams mod/con boiler to me. What are your fuel bills like? Side note: a 74°F air temp from a radiant system is quite warm.

The boiler is a 9 yr old Burnham Series 2, rated 84%AFUE, 164/136MBH in/out.

At that age and with that much oversizing, I would question the utility of spending that much money on added valves and controls and give serious consideration to a boiler upgrade.

Lynnwill

SWEI

I could not agree more on the mod/con idea. My home is older (1930) in a neighborhood of older homes. My wife WILL NOT let visible steam plumes leave the side of the house. No mod/con uses a chimney. I like the house and want to continue to live here without eviction (wife)!

I also agree that 74 degrees is high. I am near Philadelphia. If I use 14/72 for calcs. The total heat loss with those settings is approximately only 75MBH. There has been all new double pane wood windows and insulation added over the last 9 years.

My fuel bills are very high and the comfort level leaves something to be desired. That is why I am looking at piping alternatives. BTW... I think a differential pressure bypass valve should be added to the proposals to allow additional flow through the boiler if only the radiant is callings for demand. That allows a 3-way actuated mixing valve in each scheme.

SWEI

Not sure if Dave Yates services your area or not, but Jim Pompetti looks very close.

icesailor

Don't be surprised if your investment in high tech equipment doesn't give you the ROI you expect. If "5/74" means 5 degrees OAT and 74 means 74 degree IAT, you are maintaining old folks temperatures in Nursing Homes. That's rather toasty for inside comfort. Unless you have an extremely drafty house. That drops your 100.000 BTU heat loss. If you are trying to maintain 74 degrees, you end up with a very unevenly heated house. 70 to 68 degrees is a more reasonable temperature for comfort. Especially in a non drafty house.

You have radiant already installed? They used to advertise that as only needing lower temperatures like 68 degrees for comfort. If you have rooms with radiant, that won't maintain 74 degrees easily, those rooms suck heat from the older rooms with extra available heat. Its how it works.

I'm not Negative Nick. I'm just telling it like I have seen it.

I did work for years in a nursing home. They kept the temperature at a minimum of 74 degrees because old folks can't regulate their temperatures.

Lynnwill

Icesailor

I appreciate your comments!! You are correct. My temps are old folk approved. It is the most important reason for the proposed upgrades. ROI will be a secondary benefit. I find that at 74 or even 75 degrees the house becomes comfortable. Otherwise I may as well have a forced air system. The rads get warm, then cool completely, then get warm again. At the old folks temp setting the rads tend to stay warmer and heat is more even. Exactly what a rad system should NOT do. It seems my "proposal #2" may be best. I also see no compelling reason for P/S for essentially one zone.

Lynnwill

Hatterasguy

Do you think I can eliminate the boiler pump shown in "proposal #2"? I could end up with two pumps in serial connection otherwise. I agree that I should be able to connect directly to the 4-way valve and not go P/S on the single main zone. Lastly, should I even be concerned about the small radiant zone and resultant system flow? With indoor temperature feedback, constant main zone circulation (more or less) and reset, it seems that it should not be a problem (no need to add differential valve).

I will look into the chimney containing the mod/con piping but I also do not want HVAC guys on my 10 year old pitched slate roof.

SWEI

Lynnwill said:

My temps are old folk approved. It is the most important reason for the proposed upgrades. ROI will be a secondary benefit. I find that at 74 or even 75 degrees the house becomes comfortable. Otherwise I may as well have a forced air system. The rads get warm, then cool completely, then get warm again. At the old folks temp setting the rads tend to stay warmer and heat is more even. Exactly what a rad system should NOT do.

With constant circulation and properly tuned ODR, you will get that wonderfully even heat at whatever temperature you choose. When you get it right (which can take a bit of fiddling) the thermostat becomes just a high limit control.

Paul48

You put a new slate roof on? If that's true, I don't even want to guess how much that cost you. Thirty years ago we got $100 a tile to repair.

SWEI

Hatterasguy said:

Actually, after reviewing it extensively, and perusing both Taco and Tekmar, it does appear that you need p/s on one side. The preferred side seems to be the boiler side.

I've yet to see a cogent explanation as to why this is necessary for a boiler with low HX head loss. Did I miss something?

Lynnwill

Paul48

A tree fell on the house. Insurance claim - loooong story. Yes there is a full and complete new Vermont slate roof (green and some red) on the house. That is why I do not want anybody up there. I am sure there are some small houses that cost as much as the roof but it should last 100 years

I am trying to absorb the comments by Hatteras. I can not be more thankful for the careful time taken to review.

Paul48

Lynnwill.........You didn't respond to my posting the directions for the thermostatic mixing valve. I posted that, because your depiction of your existing in floor radiant mixing valve is not right.

Lynnwill

Paul48

I did see the post. The existing radiant floor 4-way mixing valve is by "Infloor" model TC62D. I did screw up the drawing connections however -- incoming supply at left (with flow check), outgoing supply on top, incoming return at right, outgoing return to system at bottom. Sorry for the mistake.

Paul48

No...Sorry I bothered you. You drew it as a 3 way in one drawing. We see them installed like that, all the time. Good Luck

Lynnwill

Hatterusguy

Does the attached come closer to what you have seen?

Lynnwill

Of course I meant Hatterasguy

Lynnwill

Thanks for the help. It is mind blowing to get real help and comments from serious, experienced professionals. I look forward to getting this done. 1 degree and 3 degree overnight temperatures are expected this week. The modifications may have to wait a little bit !!!

icesailor

Lynnwill said:

Icesailor



I appreciate your comments!! You are correct. My temps are old folk approved. It is the most important reason for the proposed upgrades. ROI will be a secondary benefit. I find that at 74 or even 75 degrees the house becomes comfortable. Otherwise I may as well have a forced air system. The rads get warm, then cool completely, then get warm again. At the old folks temp setting the rads tend to stay warmer and heat is more even. Exactly what a rad system should NOT do. It seems my "proposal #2" may be best. I also see no compelling reason for P/S for essentially one zone.

Regardless of what the OP does or doesn't do, or what is in place, the radiators should NOT be getting warmer and colder when the thermostat is set for 74 degrees, and the room only gets to 64. The thermostat should be keeping the circulator running for as long as the call is going on. The description is of a system that has something taking priority over the radiator heating zone. Radiators should never get cold on a call for heat. That's why the OP is cranking the system so high. It feels cold and drafty when the pump is off.

This sounds like it might be a case for an entire new heating system to solve the issue of a conflicting control. Or why some of us Plumbers/Heaters hate undersized boilers with multi-zone controllers with priority switches turned to ON. We turn them OFF so they don't interfere with the heating in mixed systems. Is this the same system/OP with a house with 10'+ ceilings? Radiant works splendidly with really high ceilings. Especially when the floor isn't big enough to get enough tubes in it. Heat flows to cold. The heat from radiators flows to the cold rooms with the radiant floors. Sometimes, you need to close doors.

In my opinion (minor of course), the marriage of a low temperature radiant system into a high temperature system can lead to a divorce. Or an amicable separation if you stop giving priority to things that don't need it.