Need quick advice, please

[notahandyman]

We discovered swelling bricks around the base of our chimney in the basement and called someone out to give us an estimate and possible cause. Our furnace was replaced a year ago and rerouted directly outside through the wall, rather than through the chimney. We were told at the time a new liner in the chimney wasn't really possible because of the age and size of the flue, so he went direct. Now, we're getting swelling bricks at the base of the chimney and it was determined that the vent on the water heater (vented through the chimney) is not the correct size for the BTU's being used. As a result, the water vapors aren't getting enough suction to pull them all the way up and are falling back down, causing moisture at the bottom. Also, he found deposits on the inside of the HWH vent and put a lighter to the edge of the vent. There was no pull on the flame toward the center of the vent, so he said we're not getting the CO2 vented properly.
His recommendation is to put a liner (HomeSaver Ultra Pro) in the flue and change the size of the vent on the HWH. His charge for this is around $2000. This would also include the repair to the mortar and brick and a raincap on the top.
He also told us the furnace guy lied about the liner just so he can route the furnace direct, which in the end costs more money.
Does this sound legitimate to everyone? He's scheduled to come out Sat. to do the work.

Thanks for your help.

[LazyPup]

Your second contractor is absolutely correct.

Any flue, whether it is a flue pipe or chimney relies upon the hot gases in the flue to create a thermal lift, which we commonly call the 'Draft". The rate at which the hot air rises depends upon the temperature differential between the ambient air temperature and the temperature of the flue gases. In a nutshell, the hotter the flue gas, the faster it will rise.

When your burner is firing the hot exhaust gases from the burner could heat a flue to the point where it creates an excessive draft, which would then result in sucking outside air through the combustion chamber having the same result as fanning the fire. If left unchecked that would result in dangerously overheating the burner, tank flue and the chimney or flue pipe system. In order to prevent overheating the flue naturally aspirated water heaters are required to have a "Draft Hood". The base of the draft hood is open to atmospheric air so that as the hot gases rise in the flue it can draw in some outside air to prevent the flue from getting too hot. (on a furnace flue they have a draft relief damper on the flue stack. For residential furnaces the draft dampers are generally gravity controlled by a built in weight, while on a larger commercial or industrial furnaces the draft damper is thermostatic controlled and power driven)

The Mechanical Codes are very strict in regards to the size, length, pitch of horizontal run, ratio of horizontal to vertical length and overall height of the vertical rise on flue pipes.

When the water heater burner is firing we generally have no problems with flue draft however; during those idle periods between firing the only heat being supplied to the flue is the slight thermal energy from the pilot flame, a small amount of thermal energy being radiated into the water heater flue from the stored hot water in the tank plus a very minor amount of heated room air that gets in through the combustion chamber or the draft hood.

If the size of the flue pipe is too big, or especially when a water heater is vented into a masonry chimney the rising flue gases cool too quickly and their is not enough thermal rise to lift the combustion bi-products to the top of the chimney. This causes a number of problems. 1. The water vapor in the flue gases will condense on the walls of the chimney or flue pipe. 2. It does not carry the carbon-monoxide out of the structure and 3. There is a very slight amount of sulfur-dioxide in the flue gases that will combine with the water vapor and form sulfuric acid, which will then eat away at your flue pipe or chimney.

In order to insure a proper draft the Code states that the diameter of the flue pipe must be equal to the diameter of the collar on the top of the water heater draft hood.

When connecting to a chimney the International Residential Code stipulates that the total cross sectional area of the chimney may not exceed 7x the cross sectional area of the flue pipe. (Under the Uniform Plumbing Code the cross sectional area of a chimney may not exceed 4x the cross sectional area of the flue pipe.

In my humble opinion your heating contractor elected to take the lazy way out, at your expense, whereas the second contractor is being totally honest in regards to what should be done.

[notahandyman]

Thanks very much, Lazypup! I appreciate your quick reply. We have a friend who thinks this price is too high. But when I consider what could happen if we didn't notice this or let it go in hopes of a cheaper price, I think this is a fair price. This includes the liner, mortar repair, new vent and chimney top (and labor, of course).

Thanks for your reassurance that this is the correct action to take!

[notahandyman]

another question

The repairmen came out yesterday and did the work to our chimney. I won't bore you with details on how the day went, but let's just say I won't be referring them to anyone any time soon!
Anyway, my question is, I was told one of the things they did was put some insulation inside the chimney around the vent. Can you explain this to me and how much they were to use? What's it's purpose and how much is normally used for this?

Thanks in advance for your time!

[HayZee518]

purpose of the insulation is to keep the flue warm. without it the air surrounding the flue would be cold. it all has to do with establishing a draft as hot or warm air rises and creates an upward air flow for the exhaust. the workers houldn't cram it in tight but a certain amount of loose tamping is better than really ramming it down.