LAARS MASCOT FT 140 k model

Mez

I have 2 units of the mascot ft 140k boilers ( side by side). I have an issue with heat for one unit. 

The domestic hot water DHW works fine, however there is no heat. When you call for heat the unit turns on and you can see the flame inside the exchanger, however there is no circulating hot water. 

I had this issue last year with the other unit and it was the 3 way valve. However last year the unit displayed an error msg, which isn’t the case this time. 

There is only one zone on this unit supplied by a webstone circulating pump. The pump seems to work when compared the to the other unit. 

I included some pictures below. 

Couple additional info, The baseboard doesn’t have any relief valves, could air in the system cause this. 

Could the 3 way valve be the issue even though no error msg, or even the unit internal pump.
any help will be appreciated. Thanks


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Ironman

I was working on the exact same model boiler yesterday.

You need to confirm whether or not you have flow in the house loop before assuming that the 3 way valve is bad.

Mez

And how can you do that. I checked the  circulating pump electrical and it get power when I call for heat. 

Ironman

With a heat call, feel the temp of the system supply and return lines a few feet past the boiler. There should be about 15-20* difference after it's been on for a while.

Then feel the supply and return coming out of the bottom of the boiler before the manifold. They should be about the same as the system lines. If they are extremely hot, and the system lines are substantially cooler, then you don't have circulation on the system side.

Mez

Thanks bob for getting back to me. So I had the unit running for 15 min. Pic 1

The pipes inside the unit are hot, the pump is hot too.  Pic 2
However the outside piping is cold 56deg ( basement temp) pic 3

GroundUp

If the DHW function is working, the internal circ is flowing water. This is a very common issue with these, the 3 way is stuck. They don't always throw an error code

Mez

Thank you very much for the reply Groundup. It seams like it’s the 3way valve. 

I purged the lines, I descaled the exchanger. I also checked the zone circulating pump and it seams to work. I will give the 3 way valve a try

Ironman

If the pipes between the the bottom of the boiler and the manifold are both hot, then its not the 3 way valve, its a SYSTEM circulation problem.

There's also a strainer at the pump inlet on the bottom of the boiler. Caution: you have to valve off the boiler and depressurized it first.

Mez

Thank you guys for the insights. I ended up replacing the 3way valve, and it’s working good. Now the zone pipes and heaters are hot, a Temperature are about 112 to 95 ( in - out). 

If someone this issue in the future there is a good video on YouTube
 https://youtu.be/9eJdG3bG84k 
Or you can just type laars mascot 3way and come right up. 

For those who took time to provide their expertise, thank you very much. 

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BillyO

Ken Resnick is the Babe Ruth of Laars service, I am naming my next child after him!!!

GroundUp

Ironman said:

If the pipes between the the bottom of the boiler and the manifold are both hot, then its not the 3 way valve, its a SYSTEM circulation problem.

There's also a strainer at the pump inlet on the bottom of the boiler. Caution: you have to valve off the boiler and depressurized it first.

The piping between the boiler and the purge tee was cold

Ironman

All that rust is not a good indication. It's probably the cause of the failure.

That system needs to be properly flushed and cleaned and a dirt mag installed on the return. Also, any leaks need to be located and repaired.

Mez

Bon,
i did flush both the heating and the DHW loops using city water, is there some kind of liquid that can be Introduced into the system to clean the inside pipes?
i already descaled the exchanger

BillyO

HTP and Laars same problem. Changed 6 3way valves in last 3 years. Horrible engineering

Ironman

Fernox boiler cleaner + a dirt separator on the return.

Ironman

All that rust indicates oxygenated water. That mean there’s a leak(s) that needs to be fixed.

Le John

I’m wondering why more manufactures don’t use the Caleffi made three way valve that is in the Lochinvar Noble combi.  

Le John

BillyO said:

Ken Resnick is the Babe Ruth of Laars service, I am naming my next child after him!!!

@BillyO Ken and Rathe Associates is a great representation of a boiler rep that knows the Laars boilers and helps its customers with questions or problems whenever and however they can.

EzzyT

This is one of the reasons why we shy away from wall hung combi units. To much reliance on poorly manufactured components to operate once heating or cooling equipment.

Mez

The cost of the 3 way valve is around $80, and it’s covered by the warranty. Actual replacement $, out of pocket. Go figure! These manufacturers come up with crappy products and hide behind their warranty. 

PeteA

I know this is a few years old but I’m considering one of these and I’m curious these still experiencing similar failure points in the 3way valve like some of the other posters say? I love the idea that it seems like it’s easy to work on and parts are available and normal O rings everywhere 

hot_rod

Looking at the water in the bucket and the rust build up inside the valve body, that is not a manufactures defect. A squirt of conditioner in every boiler you install could prevent most of these type of failures.
Assuming the system is leak-free