Reverse flow through hot water boiler

DaveGateway

Have a gas fired hot water boiler with baseboard loop, single zone. I want to reverse the water flow through the system by flipping the circulator pump around 180 degrees (currently located on the return). Other than relocating the high limit control, what else must I do?

Would greatly appreciate your collective input.

ScottMP

Why ?

what are you trying to accomplsh Jack ?

More info please.

Scott

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DaveGateway

I was afraid that someone would ask that question! It's the customer's idea. He thinks that by reversing the flow he will loose, or at least lessen, the expansion noises that he hears inside of his walls. Unfortunately, we inhereted this job. We've already explained that it probably won't make any difference, but this gut is a real hard head.

jackchips_2

There are

two good ways to decrease the expansion noises.

You can go to constant circulation to decrease the temperature swings or find where the noises originate and eliminate them.

If he insists, you may want to at least put the circulator on the supply (pumping away-do you own the book yet?). Although if the problem is out in the system (pipes rubbing somewhere, hangers to tight, etc,) it won't solve the problem.

This is the simple response, others will probably give you more detailed information.

Good luck.

DaveGateway

Yeah, it is a system problem. From the sound of the noise the installing contractor probably forced a 3/4" pipe through a 7/8" hole(s). The only way we could improve on the real cause of the problem would be to open the walls and some of the ceilings. Unfortunately, we're left treating the symptoms and not the cause.

Someone told this customer that reversing the flow would solve the problem. We tried to talk him out of it but, like I said, he's a real hard head, but he's willing to pay. I'm just concerned that if I do reverse the flow that I won't create another problem.

Thanks for your input.

ScottMP

Jack

The rpoblem is the temperature is the same ( or near enough ) that from the return or from the supply your going to get expansion. Its not flow its temperature difference.

Jacks on the right track. Constant circ or outdoor reset which would lessen the temperature of the supply water is the only route, besides opening walls.

If he dos'nt understand, let him hire some one else because once you touch it, you own it.

Good Luck

Scott

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Carl PE

How about?

Instead of messing with the boiler, which I think is probably not a good idea.. why don't you switch the supply and return piping to reverse the flow through the system?

Make sure your checks and zone valves are all headed the right direction, though..

ALH_3

Control

A tekmar 256 or 260 may help, but most likely wont eliminate the noise without opening the walls and ceilings like you say. There is a slim chance that the return is better isolated from the wood than the supply line. I'd re-pipe rather than flipping the pump.

Tekmar 256 Data Brocure

Tekmar 260 Data Brocure


-Andrew

Weezbo

i'd defer.....

if you have some weak lttle boiler it may have built in flow regulator or some such gizmo...if its an iron boiler the location of the pump ,piped correctly at the boiler wouldnt make any difference any way ...making a bypass with an i-series S setpoint control would keep the tempered water comming back a consistent temp for boiler protection,if you dont have constant recirc it will stand alone powered by the boiler pump(in conjunction with a call for primary pump,)that way any call for heat will open the zone And the I-seriesS and work sorta like a circuit setter while protecting the boiler.noises in the "Field" are more often than not due to poor installation practises or lack of squeakers etc...Reducing the temps into the "field"can quiet the shock factor also depending on the header size there are lots of various stradgeies to do that..still there are no Magical Boxes to solve all expansion noises.different systems have their own seperate anomalies...

Paul Brockfeld

Do not reverse the flow thru a Weil-McLain Boiler

You don't say what brand of boiler you're dealing with but if it's a Weil-McLain, I do not recommend trying to reverse the flow thru the boiler. One of my contractors (I'm the boiler salesman for a wholesaler in St. Louis, MO) accidentally reversed the flow thru a Weil-McLain CGa series boiler on a baseboard loop system. He did not pay attention to the flow arrow on the pump and installed it backwards. The system made so much noise it would wake the homeowners at night. Once we switched the pump to flow the correct way thru the boiler, the noise went away.

Joe@buderus

If the boiler is a Buderus Boiler, we do have a concern with switching the supply and return (depending on model and design). If the boiler is a Buderus please call us at 1-800-283-3787 and we can assist.

Because we do a lot with outdoor reset, I would suggest pursuing this course. It will create less noise, be more comfortable and could save money in fuel cost.
Good Luck!

ScottMP

Carl

What good will come from reversing the flow ??

Scott

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Carl PE

Probably none. But, it sounds like that's what the guy wants.

Anyway, I thought I'd propose it as an easy way to show him that changing the direction of the flow isn't going to solve his problem.

I think we all have a pretty good idea what the problem is here and how to actually fix it, but sometimes you have to humor the guy signing the ticket.

bob_25

reverse

for what it's worth weil mclain has a book titled "Nomal Flow Versus Reverse Flow In Cast Iron Boilers" supplement to section IV of engineers reference manual. Form No. EM316 R1. In short don't do it. bob

Unknown

What about those expansion fittings ?

They look like a copper accordion . Anyone ever use them and do they work ? My baseboard makes some music too .

Weezbo

Ron, they do indeed work on 1 1/4 commercial slant fin

i always find a place for them:) they are just that good:)i'd even recommend their use. however in the reverse the flow will solve everything the homeowners insisting our man do there isnt a magic bullet to cure it. you can lower supply temps on the tri aquastat then this then that then another ...he inherited the job and naturally the homeowner figures What do He know?anyway...kinda deal.a long time ago some guy insisted i do such and such and i said well...you pay me to do your idea and if that dont work you pay me to do mine...it urinated the guy off when it took me hours to do what i had suggested and took nearer half the day to frick things up even more listening to his estranged advise:)buh its only money it is best to leave it alone when you are being told that you dont know What You are doing ....because face it if we were so smart What on Earth are we doing there in the first place:)

Robert_12

noise

had to fix simular problem before no way to get away from it but can be reduced 80%. out door reset and if you don't have any zone valves run pump all the time. if you have zone valves figure what zone is doing it.and where if possible work silicone(arisal) around the pipe or some kind lub around it. have made the zone master with other zones slaves with pump on all the time.

S Davis

Tekmar 262

Why not use a Tekmar 262 it has a feature called soft start that raises the supply temp slowly and will help with most of the expansion noise.
It has worked on a couple of problem jobs I have been asked to fix.

S Davis


Apex Radiant Heating

Carl PE_2

Clarification

I re-read my post, and it doesn't make as much sense as I thought it did.

What I was suggesting was to leave the near-boiler piping alone. DO NOT reverse the flow through the boiler itself, but switch the SYSTEM supply and return.

Does that make more sense?

Yes, I know it's not going to fix the problem.

Mike Reavis_2

Because you live here, in the good old USA you can do this.

You can also be hauled into court, atempting to explain why you decided to put your knowledge above that of the design engineers at the boiler makers lab. Way to much liability. just my opinion.

Mike