draft regulator

sidney r. bray

My Weil McLain HE 5 boiler has a hairline crack in one of the middle sections..they (weil mclain) suggest replacing the entire block (1987 model) or getting a new boiler..Does anyone have any success sealing these type of cracks with a certain product (we tried a product called seal master, but to no avail). Also, the Manual J Heat Loss method for calculating the proper size boiler, has anyone ever heard of it vs sizing your sq.ft. of radiation & piping?? It sounds to me like you wouldn't have to size your radiation and piping under this method, if you do, your oversizing your new boiler (per cast iron radiator manufacturer). I have mostly the older style free standing cast iron radiators in my home with three baseboard (base-ray) radiators for my hot water radiator system.

zeke

Do I need a separate draft regulator for a HW heater that is sharing the vent with the furnace? Also, is it advisable to install an interlock switch that will cut off the furnace on a call for hot water firing. The HW vent is 6" and the furnace vent is 5"

Empire_2

Q:?

What is the size of the main vent pipe and the actual size of your 2 appliances? What type of fuel are you burning?. Measurements would also help.

Jim Davis_3

One would have to assume these are oil fired. The best way to control all oil equipment is with its own draft regulator. If the flue size is smaller than 8" it is not big enough for both appliances and they shouldn't even be operated until this situation is fixed. 8" flue or bigger, no switch is required.

zeke

draft regulator

Thanks for the responses. The units are each oil fired and each has a 0.75GPH rated nozzle and 105,000BTUH output, making a combined total of 210,00BTUH firing rate when both are on.Also, they each enter the chimney stack 1 foot apart, with the 5" vent( the furnace) below, having the regulator on it. I couldn't get a dimension for the chimney, but at the cleanout it looks like about 7" square.
Jim, if you think I need a larger dia chimney is called for this, why wouldn't a simple relay cutout on the HW electrical panel work, so that only one unit is "on" at the same time?
I forgot to mention that the original HW heater(this a replacement and was installed without the damper) had a similar rating with a 5" vent and I never had a problem.

Jim Davis_3

Adding a switch to lock out one can be done. Chimneys can offer a lot of room for discussion as far as their capacity. Most are rated by BTU's versus area of chimneys attached or common vented. But most charts assume perfectly smooth materials and no deteriation. One way to see if the chimney is actually adequate is to test the draft above the barometric when one appliance is running and then both. If the draft maintains or increases the chimney is adequate for at least the conditions of that day. If the draft drops then the chimney is inadequate. No matter how many rules we write, inanimate objects perform however they choose.