Gas and Oil Home Heating Furnaces - Weil Mc Lain Ultra Boiler Install

Hi All


I need some advise on the primary/secondary setup. Is a second circulator requied on the primary side and how do I wire it into the boiler, should both circulators run at the same time? The exisiting system is a converted gravity feed setup with one circulator and a 2 diaphram expansion tanks, the house is two story with heat loss calculated at 58,000 BTUH (25% overload).
Recent improvements are r-30 attic, r-13 sidewalls and vinyl 2 pane replacenent windows. When I do my startup can I reduce the boiler water temp from the default 190 to save on fuel? The radiarors are the old style 5 tube and are rated 3 1/2 times what is called for in each room.

The boiler is an ULTRA 105 with a dedicated 40 gallon domestic hot water attached.

Do you use a seperate circulator for the indirect water heater? Or do you use a zone valve? You will need either one or the other for the primary/secondary. If you use a circulator and a flow check, the reverse aquastat will prevent you from removing all the hot water from the boiler. I also recommend a bypass loop on the boiler. That way you have an even temperature throughout the boiler and do not have to throttle the return from the main loop too much. You can probably reduce the high limit temp from 190 to 160 and the low should stay around 130 to be able to provide domestic water in the indirect without too much of a preheat. What stage of the installation are you at now and what changes are you planning?

I will be using a circulator for the DHW and 2 flow checks one after the DHW circulator and one above the DHW tee in the boiler system supply but before the system circulator. Three circulators will be used in the complete system.

I have just begun my install and am getting the units in position. I opened the boiler up and inside were installation instructions and they do show provisions for additional circulator hookups.

Do I need the bypass loop even with the pri/sec connection?
Weil Mc Lain shows the boiler circulator below the pri/sec connection on the return line to the boiler. How would I pipe the bypass if needed?

My present boiler is fed by 1 1/4" copper but the new boiler connections are 1". Should I continue with the 1 1/4 or is 1" OK to plumb to the new installation from where the old one is terminated.

Thanks for your expertise your help is greatly appreciated.

You can stay with 1" pipe. It will handle all the btus your boiler can make.


I would strongly recommend the bypass loop. You can always close the bypass valve all the way and forget you ever installed it, but if you don't install it, you're limiting your options. If you install the boiler circulator as shown (which I think is a good idea in a primary/secondary system, you would add a tee under the circulator (on the boiler side) and another tee as the first fitting off of the top of the boiler. That would create a loop where some cold return water can be diverted around the boiler and prevent the circulator from cycling on low limit. Then with the bypass full open and a system full of cold water, start throttling the bypass a little at a time until the low limit cycles and then open it slightly. You may also need to throttle the boiler supply (or return) to the big loop. The boiler should meter in as much hot water as it can make without cycling. The benefit of the secondary loop is that all radiators will warm at about the same rate and heating will be even. They also do not need to get to 200 degrees at any time.

As a matter of preference, I use zone valves. It seems odd to have 3 circulators and then have to throttle valves to prevent too much circulation. Two circulators and 2 zone valves would work nicely too but you are on the right track.

Be sure you plumb in the boiler supply and return to the secondary loop on the same side of the secondary circulator, not on opposite sides as might seem logical.

Ken

Your question on why i'm using 3 circulators. there is one downline of the pri/sec connection on the supply side another on the return side below the pri/sec and one for the dedicated DHW. You suggest installing the bypass below the first fitting above the boiler. Will this affect my DHW circulation? They show DHW tee's as the first fittings.

Weil Mc Lain shows 2 flow checks one above the DHW tee on the supply side of the boiler but below the pri/sec connection and another between the DHW circulator and DHW unit. Would it help flow to place an additional flowcheck in the return line from the DHW unit, between the DHW unit and the boiler return line tee?

Thanks for your help!!!!!

Each loop usually requires a circulator, flow check and a thermostat to control the pump. Having 2 flow checks on one loop would be no benefit. I wish I could draw a picture for you. One pump just moves water around the secondary loop and that one does not need a flow check or a control. I would suggest slaving that pump to the pump on the boiler. That one will only run on a call for heat and so will the secondary loop pump. You would have to pay special attention to piping to have the boiler pump and the dhw pump take advantage of the bypass loop.

The install is coming along very nicely but I have several questions about component placement. The DHW tank is plumbed into the boiler and the boiler runs are in place up to the pri/sec connection. Will it make very much difference if the pri/sec is placed horizontal along the (low) ceiling? I did not have enough room above the boiler vertically with the bypass and boiler circulator located in that area. The existing setup has two 3 gal. diaphram tanks one on the supply side and one on the return I would like to maintain this setup. Weil Mc Lain shows the regulated fill valve and air separator and backflow preventer on the supply side and this fits the layout pretty good any suggestions?

I don't have a good understanding of the throttling of the bypass what do you mean by low cycling?

Thanks for the help.