Question # 3 for Glenn Harrison and others

Unknown

This is a Self Generating System (Powerpile or Thermopile are other names for this systems). It uses a 750 millivolt pilot generator. This is a steam system. The customer claims that when they get up in the morning and turn up the thermostat the boiler will not come on. This has been occuring for the last week or so. The outdoor temperature has been hovering around zero to 10 degrees during the night and into the early morning. When the technician arrives at 10 AM in the morning the boiler is running and making steam. He feels the customer is perhaps doing something wrong and tells them the system is running and everything is okay and he leaves. The next morning the same problem occurs. This time when the tech arrives around noon it is running again. He decides to take some millivolt readings:

His readings

Open circuit 710 Millivolts

Closed circuit (controls calling) 410 mv's

Closed circuit (controls Jumped out) 250 mv's

TH reading 175 mv's

Thermostat TS-86 115 mv's

Pressuretrol 0 mv's

Low water cutoff 0 mv's

30 feet of 18 gauge wire 60 mv's

Pull in on gas valve 315 mvs

Drop out is 95 mv's

He checks his gas pressure at the inlet of the gas valve 7" W.C. at the outlet is 3.5" W.C. He cleans the pilot and
he leaves the system running. It has now come in again this morning. They claim it was off when the got home last night at 6 PM and has been off all night.

You are the tech who has been sent on this no heat call, what would you do?

J.C.A._3

I wish.....

They would make an "On Watch" type system for gas boilers, with all the different variables programmable.

But, I guess I would be checking the size of the gas piping, thinking that during the overnight call, it may be enough to keep the pilot lit, but with all the other calls for heat in the neighborhood may be keeping it on the edge.I would also check the controls in the "train", concentrating on the LWCO . (plugged pigtail with enough restriction to let the steam in, but not the pressure out).

Again, just a guess, cause I don't (or never will) know enough. Chris

paul lessard_3

Is the pull in#

A little high?

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Unknown

I want to wait

and give everyone a chance to try this one so everyone be patient.

lchmb

How about the gas regulator freezing up at night?

Unknown

No high pressure

regulator on this job. The gas pressure is low pressure in the mains. Normal pressure in those systems is between 7" W.C. to 10" W.C.

S Davis

Water

Water in the main coming into the house freezing at night?
Now that I think about it the pilot would go out so guess again!

S Davis


Apex Radiant Heating

Kal Row

to a hammer everything looks like a nail....

let me guess - this too is about gas pressure.

why is the outlet 3.5 - lets see - everything is ok during thet day when the neighborhood is not using and the pressure is up – usually water in the local lead-in

though if pressure at test port would be good and the pilot is properly adjusted, the open pile should be 750mv - 410 closed is a bit low, 500+ is the norm

if he cant fix the gas supply problem:
there is a new GV from RobertShaw the 7000mvlc that pulls in at 100 and out at 15 - how's that for a dangerous suggestion

Rookie_3

Powerpile test

multi-tester settings, black lead minus and red lead positive, pointer set on 1200 M.V. range......connect leads to PP terminals on the gas valve, with the T-Stat NOT calling for heat reading should be 540 M.V..
Turn T-Stat up closing the control circuit. Connect leads from the tester to TH. TH. terminals on the valve. The maximum reading should be 160 M.V., if not the valve is no good.
If the readings on PP and TH. TH. on the valve are the same, one of the controls on the control circuit is open. check the readings on each control and when you get the same reading that you got on PP on the valve that is the one that is open.
The T-Stat is the only control in the circuit that should read higher than 10 M.V..
On a T86A the readings may be as high as 90-100 M.V..
Magnet drop out should be MAX. 90 or less.

don_47

The

gas company forgot to add propane to the natural gas to
keep the pressure up when it gets this cold,or either they
did and this could be the reason for the intermitted problem.

chuck shaw

i would try to make arrangements,

with the homeowner, to get there at a time when things are not working....6PM for example, and do gas pressure tests etc. then. Nothing like trouble shooting a fault, in the conditions when it happens.

Tim, if I were to approach it this way, what would I find for gas pressure?

Chuck

Unknown

The reading of 500 MV's is

too high what you are reading is the drop through the pilotstat and that is not necessary unless you are having pilot outage.

I find that many people do not know how to correctly troubleshoot powerpile systems. The 410 reading is actually too high. If you chart out the 710 mv's against the 410 it will show you that.

That Robertshaw valve to the best of my knowledge is designed for use only on decorative appliances. It should not be used as a replacement for central heating valves.

Unknown

Chuck Shaw & others

good idea Chuck but really not necessary with the information given. However to answer your question the pressure at 6 PM would possibly be low.

Unknown

Dan your way of testing

and getting 540 is actually testing the pilotstat on the gas valve it is not testing the valve coil.

All readings taken with a millivolt heating system should be with the thermostat calling. The only time you want to shut the thermostat down is to do the check on pilotstat and that is only if you have a pilot outage problem.

Your 160 MV reading does not add up. Here are the numbers

TS-86 115 to 135 taken right from Honeywell engineering sheets

30 feet of 18 gauge wire 60 mv's

Max 10 mv's per control max so that is 20 Total should be between 175 to 205 any thing less than 175 is good.

The rest of your readings do not take the valve coil into consideration.

But anyway based on your readings what is wrong?

Unknown

Good guess Don

but this particular utility does not use Propane but LNG for peak shaving. The mix is fine.

Years ago when we used propane it solved the lack of gas problem but sure created other problems.

Glenn Harrison_2

Let me try...

If I understand the way your taking readings, You take your open circuit reaindg of 710 milivolts, and subtract the 410 mv closed ciruit reading, which leaves you with 300 mv. You are saying the valve opens with 315 mv, so you are running a little short so sometimes the valve won't open.

Another way I look at it in case I'm misinterpeting your readings, is that if I remember correctly, 315 mv to open a valve is to much anyways, so the coil is weak and the boiler needs a new gas valve. I have seen valves open with 200 mv.

Unknown

Glenn No adding or

subtracting. The only correct way to troubleshoot powerpile is to chart out the readings with charts provided by Honeywell.When it is charted out the 710 OC to 410 CC (controls calling) matched to the high pull in the valve coil is weak.

You are correct as was Paul Lessard earlier that the Pull in reading is high. Powerpile valves should pull in between 179 to 320 mv's.

Here is the solution to the problem:

With the extreme cold weather the gas pressure during high usage times (early AM and around supper time) will be reduced. The pilot is on line pressure so the pressure to the pilot is reduced. This causes the Open Circuit reading to drop during this time. Minumum open circuit for these systems is 540. As the drop in MV's takes place and the valve coil being weak. Not quite over the maximum pull in
range which is 179 to 320. What happens is the the valve can not open. When the pressure goes back up there is enough increase in MV's to cause the valve to open.

Solution is to install a new gas valve. The pilot was cleaned and the generator is putting out enough MV's so this should solve the problem even if the pressure drops down.

Kal Row

yeah - the 7000mvlc was a bad joke..

if a downdraft blew the whole show out, at a 15mv drop out, it might just take a while for the valve to close and leave a dagerous amount of gas in the box

my experiance is week on mv system hence my hi CC voltage recolection.
i wonder though - what the legality is, of just retrofitting the whole system with the new honewll 95xx smart valves - with HotSurfaceIgnition and flame rectification, seems to me, that such a system would be more forgiving to gas pressure fluctuations

Kal Row

yeah - the 7000mvlc was a bad joke..

if a downdraft blew the whole show out, at a 15mv drop out, it might just take a while for the valve to close and leave a dagerous amount of gas in the box

my experiance is week on mv system hence my hi CC voltage recolection. i wonder though - what the legality is, of just retrofitting the whole system with the new honewll 95xx smart valves - with HotSurfaceIgnition and flame rectification, seems to me, that such a system would be more forgiving to gas pressure fluctuations

Kal Row

how responsive are a Gas co's to \"their\" pressure problems..

you teach a lot of people from all around - wonder if you have a feel about that in various locals - i think service people are reluctant to call them - just in case they forgot to dot some I or cross some T, and have the gas co just lock it down for inspection - once you bring them in, they go looking at everything connected to the gas line (as well you should have) - i personally like their input - in my area they are way too lax - they ok lots of things thay shouldn’t (a better way to spell "they" - English spelling is illogical - some, home)

Unknown

Kal it depends

on the type of pressure problem. Isolated cases tend to take a while to get them to arrive. If however they have an entire area affected they do show up pretty quickly. The problem is that many gas companies are pushing equipment sales and even giving equipment away to get folks to sign on. This tends to put very high demand on the older low pressure cast iron systems in extreme weather conditions. All of your major metropolitan areas of the northeast will experince this. Ken Secor tells me that it also happens in NJ. There does not seem to be anyone putting a halt to massive marketing of natural gas as the fuel of choice when in fact the utility has continuing problems in certain areas. We may also be looking at shortages in natural gas itself in the very near future which will push the price even higher. I am against the production of electricty using natural gas to me it is a waste. Coal should be the fuel of choice for that production. With modern "scrubbers" and environmental protection available coal is not the demon fuel it once was. We have two very large coal plants near me and they have no pollution problems at all.

Unknown

Kal SmartValve cannot

be used as a retrofit system. It does not matter anyhow because pressure problems affect every type of system. One is no better than the other in those situations. A drop in pressure will pull the flame away from the flame rod and the system will shut down and then keep going thru attempts to relight until the pressure comes back up.

Unknown

Well those are my three

questions that I often ask folks about gas systems. All in all you Wallies did pretty good, but I sort of expected that. If you found your self totally lost on the three questions then you probably need some training.

I will do some more of this some other time.

By the way I bookmarked the three posts on the questions so if anyone wants to see them in the future I will have them.

Rookie_3

What's wrong?

Couldn't tell you Tim!!! I do oil not gas. I pulled out a data sheet from a night course I had taking on gas heat that I thought might help you out on the powerpile. The readings off that came from an instructor that was employed by Boston Gas(Keyspan)I guess I was wrong assuming they new what they were talking about?

Rookie_3

Kal Row

mega-dito on gas-elec generation, what a huge waste!!!!!

i can only see it for emergency backup only - and even then, the deisels are cheaper - so the power density is smaler and you need more of them, so what - are we that tight on space? besides more "egg baskets" is safer than one huge gas turbine - dont get me started on a power rant!!

Unknown

Dan, that is interesting

as I actually did a lot of training for Keyspan Home Energy Services (Not the gas company but the service company). The ex Boston gas employees all used that method of troubleshooting which I believe came from Robertshaw. It has however proven inconclusive as a fool proof method of diagnosis and troubleshooting for Powerpile.

I taught all of them the Honeywell method using Honeywells charts and information and they found it to work much better. We used that method for years a Providence Gas Company and it worked with out a glitch.

Glenn Harrison_2

Thanks for taking the time, Tim.

I always appreciate testing of my knowledge, so I know where I'm at, and where I need to refresh the memory, or get more training. Always glad to learn something new.

Thanks again. Keep up the great work you do.